mirror of https://github.com/torvalds/linux.git
2868 Commits
| Author | SHA1 | Message | Date |
|---|---|---|---|
Sean Christopherson
|
f3ced000a2 |
KVM: x86: Always sync PIR to IRR prior to scanning I/O APIC routes
Sync pending posted interrupts to the IRR prior to re-scanning I/O APIC
routes, irrespective of whether the I/O APIC is emulated by userspace or
by KVM. If a level-triggered interrupt routed through the I/O APIC is
pending or in-service for a vCPU, KVM needs to intercept EOIs on said
vCPU even if the vCPU isn't the destination for the new routing, e.g. if
servicing an interrupt using the old routing races with I/O APIC
reconfiguration.
Commit
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Sean Christopherson
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89a58812c4 |
KVM: x86: Drop support for hand tuning APIC timer advancement from userspace
Remove support for specifying a static local APIC timer advancement value, and instead present a read-only boolean parameter to let userspace enable or disable KVM's dynamic APIC timer advancement. Realistically, it's all but impossible for userspace to specify an advancement that is more precise than what KVM's adaptive tuning can provide. E.g. a static value needs to be tuned for the exact hardware and kernel, and if KVM is using hrtimers, likely requires additional tuning for the exact configuration of the entire system. Dropping support for a userspace provided value also fixes several flaws in the interface. E.g. KVM interprets a negative value other than -1 as a large advancement, toggling between a negative and positive value yields unpredictable behavior as vCPUs will switch from dynamic to static advancement, changing the advancement in the middle of VM creation can result in different values for vCPUs within a VM, etc. Those flaws are mostly fixable, but there's almost no justification for taking on yet more complexity (it's minimal complexity, but still non-zero). The only arguments against using KVM's adaptive tuning is if a setup needs a higher maximum, or if the adjustments are too reactive, but those are arguments for letting userspace control the absolute max advancement and the granularity of each adjustment, e.g. similar to how KVM provides knobs for halt polling. Link: https://lore.kernel.org/all/20240520115334.852510-1-zhoushuling@huawei.com Cc: Shuling Zhou <zhoushuling@huawei.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-ID: <20240522010304.1650603-1-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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Paolo Bonzini
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7d41e24da2 |
KVM x86 misc changes for 6.10:
- Advertise the max mappable GPA in the "guest MAXPHYADDR" CPUID field, which
is unused by hardware, so that KVM can communicate its inability to map GPAs
that set bits 51:48 due to lack of 5-level paging. Guest firmware is
expected to use the information to safely remap BARs in the uppermost GPA
space, i.e to avoid placing a BAR at a legal, but unmappable, GPA.
- Use vfree() instead of kvfree() for allocations that always use vcalloc()
or __vcalloc().
- Don't completely ignore same-value writes to immutable feature MSRs, as
doing so results in KVM failing to reject accesses to MSR that aren't
supposed to exist given the vCPU model and/or KVM configuration.
- Don't mark APICv as being inhibited due to ABSENT if APICv is disabled
KVM-wide to avoid confusing debuggers (KVM will never bother clearing the
ABSENT inhibit, even if userspace enables in-kernel local APIC).
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Merge tag 'kvm-x86-misc-6.10' of https://github.com/kvm-x86/linux into HEAD
KVM x86 misc changes for 6.10:
- Advertise the max mappable GPA in the "guest MAXPHYADDR" CPUID field, which
is unused by hardware, so that KVM can communicate its inability to map GPAs
that set bits 51:48 due to lack of 5-level paging. Guest firmware is
expected to use the information to safely remap BARs in the uppermost GPA
space, i.e to avoid placing a BAR at a legal, but unmappable, GPA.
- Use vfree() instead of kvfree() for allocations that always use vcalloc()
or __vcalloc().
- Don't completely ignore same-value writes to immutable feature MSRs, as
doing so results in KVM failing to reject accesses to MSR that aren't
supposed to exist given the vCPU model and/or KVM configuration.
- Don't mark APICv as being inhibited due to ABSENT if APICv is disabled
KVM-wide to avoid confusing debuggers (KVM will never bother clearing the
ABSENT inhibit, even if userspace enables in-kernel local APIC).
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Paolo Bonzini
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4232da23d7 |
Merge tag 'loongarch-kvm-6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson into HEAD
LoongArch KVM changes for v6.10 1. Add ParaVirt IPI support. 2. Add software breakpoint support. 3. Add mmio trace events support. |
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Sean Christopherson
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40269c03fd |
KVM: x86: Explicitly zero kvm_caps during vendor module load
Zero out all of kvm_caps when loading a new vendor module to ensure that KVM can't inadvertently rely on global initialization of a field, and add a comment above the definition of kvm_caps to call out that all fields needs to be explicitly computed during vendor module load. Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com> Message-ID: <20240423165328.2853870-4-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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Sean Christopherson
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555485bd86 |
KVM: x86: Fully re-initialize supported_mce_cap on vendor module load
Effectively reset supported_mce_cap on vendor module load to ensure that
capabilities aren't unintentionally preserved across module reload, e.g.
if kvm-intel.ko added a module param to control LMCE support, or if
someone somehow managed to load a vendor module that doesn't support LMCE
after loading and unloading kvm-intel.ko.
Practically speaking, this bug is a non-issue as kvm-intel.ko doesn't have
a module param for LMCE, and there is no system in the world that supports
both kvm-intel.ko and kvm-amd.ko.
Fixes:
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Sean Christopherson
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c43ad19045 |
KVM: x86: Fully re-initialize supported_vm_types on vendor module load
Recompute the entire set of supported VM types when a vendor module is
loaded, as preserving supported_vm_types across vendor module unload and
reload can result in VM types being incorrectly treated as supported.
E.g. if a vendor module is loaded with TDP enabled, unloaded, and then
reloaded with TDP disabled, KVM_X86_SW_PROTECTED_VM will be incorrectly
retained. Ditto for SEV_VM and SEV_ES_VM and their respective module
params in kvm-amd.ko.
Fixes:
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Alejandro Jimenez
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6982b34c21 |
KVM: x86: Only set APICV_INHIBIT_REASON_ABSENT if APICv is enabled
Use the APICv enablement status to determine if APICV_INHIBIT_REASON_ABSENT
needs to be set, instead of unconditionally setting the reason during
initialization.
Specifically, in cases where AVIC is disabled via module parameter or lack
of hardware support, unconditionally setting an inhibit reason due to the
absence of an in-kernel local APIC can lead to a scenario where the reason
incorrectly remains set after a local APIC has been created by either
KVM_CREATE_IRQCHIP or the enabling of KVM_CAP_IRQCHIP_SPLIT. This is
because the helpers in charge of removing the inhibit return early if
enable_apicv is not true, and therefore the bit remains set.
This leads to confusion as to the cause why APICv is not active, since an
incorrect reason will be reported by tracepoints and/or a debugging tool
that examines the currently set inhibit reasons.
Fixes:
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Sean Christopherson
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1d294dfaba |
KVM: x86: Allow, don't ignore, same-value writes to immutable MSRs
When handling userspace writes to immutable feature MSRs for a vCPU that
has already run, fall through into the normal code to set the MSR instead
of immediately returning '0'. I.e. allow such writes, instead of ignoring
such writes. This fixes a bug where KVM incorrectly allows writes to the
VMX MSRs that enumerate which CR{0,4} can be set, but only if the vCPU has
already run.
The intent of returning '0' and thus ignoring the write, was to avoid any
side effects, e.g. refreshing the PMU and thus doing weird things with
perf events while the vCPU is running. That approach sounds nice in
theory, but in practice it makes it all but impossible to maintain a sane
ABI, e.g. all VMX MSRs return -EBUSY if the CPU is post-VMXON, and the VMX
MSRs for fixed-1 CR bits are never writable, etc.
As for refreshing the PMU, kvm_set_msr_common() explicitly skips the PMU
refresh if MSR_IA32_PERF_CAPABILITIES is being written with the current
value, specifically to avoid unwanted side effects. And if necessary,
adding similar logic for other MSRs is not difficult.
Fixes:
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Linus Torvalds
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817772266d |
* Clean up SVM's enter/exit assembly code so that it can be compiled
without OBJECT_FILES_NON_STANDARD. This fixes a warning
"Unpatched return thunk in use. This should not happen!" when running
KVM selftests.
* Fix a mostly benign bug in the gfn_to_pfn_cache infrastructure where KVM
would allow userspace to refresh the cache with a bogus GPA. The bug has
existed for quite some time, but was exposed by a new sanity check added in
6.9 (to ensure a cache is either GPA-based or HVA-based).
* Drop an unused param from gfn_to_pfn_cache_invalidate_start() that got left
behind during a 6.9 cleanup.
* Fix a math goof in x86's hugepage logic for KVM_SET_MEMORY_ATTRIBUTES that
results in an array overflow (detected by KASAN).
* Fix a bug where KVM incorrectly clears root_role.direct when userspace sets
guest CPUID.
* Fix a dirty logging bug in the where KVM fails to write-protect SPTEs used
by a nested guest, if KVM is using Page-Modification Logging and the nested
hypervisor is NOT using EPT.
x86 PMU:
* Drop support for virtualizing adaptive PEBS, as KVM's implementation is
architecturally broken without an obvious/easy path forward, and because
exposing adaptive PEBS can leak host LBRs to the guest, i.e. can leak
host kernel addresses to the guest.
* Set the enable bits for general purpose counters in PERF_GLOBAL_CTRL at
RESET time, as done by both Intel and AMD processors.
* Disable LBR virtualization on CPUs that don't support LBR callstacks, as
KVM unconditionally uses PERF_SAMPLE_BRANCH_CALL_STACK when creating the
perf event, and would fail on such CPUs.
Tests:
* Fix a flaw in the max_guest_memory selftest that results in it exhausting
the supply of ucall structures when run with more than 256 vCPUs.
* Mark KVM_MEM_READONLY as supported for RISC-V in set_memory_region_test.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm fixes from Paolo Bonzini:
"This is a bit on the large side, mostly due to two changes:
- Changes to disable some broken PMU virtualization (see below for
details under "x86 PMU")
- Clean up SVM's enter/exit assembly code so that it can be compiled
without OBJECT_FILES_NON_STANDARD. This fixes a warning "Unpatched
return thunk in use. This should not happen!" when running KVM
selftests.
Everything else is small bugfixes and selftest changes:
- Fix a mostly benign bug in the gfn_to_pfn_cache infrastructure
where KVM would allow userspace to refresh the cache with a bogus
GPA. The bug has existed for quite some time, but was exposed by a
new sanity check added in 6.9 (to ensure a cache is either
GPA-based or HVA-based).
- Drop an unused param from gfn_to_pfn_cache_invalidate_start() that
got left behind during a 6.9 cleanup.
- Fix a math goof in x86's hugepage logic for
KVM_SET_MEMORY_ATTRIBUTES that results in an array overflow
(detected by KASAN).
- Fix a bug where KVM incorrectly clears root_role.direct when
userspace sets guest CPUID.
- Fix a dirty logging bug in the where KVM fails to write-protect
SPTEs used by a nested guest, if KVM is using Page-Modification
Logging and the nested hypervisor is NOT using EPT.
x86 PMU:
- Drop support for virtualizing adaptive PEBS, as KVM's
implementation is architecturally broken without an obvious/easy
path forward, and because exposing adaptive PEBS can leak host LBRs
to the guest, i.e. can leak host kernel addresses to the guest.
- Set the enable bits for general purpose counters in
PERF_GLOBAL_CTRL at RESET time, as done by both Intel and AMD
processors.
- Disable LBR virtualization on CPUs that don't support LBR
callstacks, as KVM unconditionally uses
PERF_SAMPLE_BRANCH_CALL_STACK when creating the perf event, and
would fail on such CPUs.
Tests:
- Fix a flaw in the max_guest_memory selftest that results in it
exhausting the supply of ucall structures when run with more than
256 vCPUs.
- Mark KVM_MEM_READONLY as supported for RISC-V in
set_memory_region_test"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (30 commits)
KVM: Drop unused @may_block param from gfn_to_pfn_cache_invalidate_start()
KVM: selftests: Add coverage of EPT-disabled to vmx_dirty_log_test
KVM: x86/mmu: Fix and clarify comments about clearing D-bit vs. write-protecting
KVM: x86/mmu: Remove function comments above clear_dirty_{gfn_range,pt_masked}()
KVM: x86/mmu: Write-protect L2 SPTEs in TDP MMU when clearing dirty status
KVM: x86/mmu: Precisely invalidate MMU root_role during CPUID update
KVM: VMX: Disable LBR virtualization if the CPU doesn't support LBR callstacks
perf/x86/intel: Expose existence of callback support to KVM
KVM: VMX: Snapshot LBR capabilities during module initialization
KVM: x86/pmu: Do not mask LVTPC when handling a PMI on AMD platforms
KVM: x86: Snapshot if a vCPU's vendor model is AMD vs. Intel compatible
KVM: x86: Stop compiling vmenter.S with OBJECT_FILES_NON_STANDARD
KVM: SVM: Create a stack frame in __svm_sev_es_vcpu_run()
KVM: SVM: Save/restore args across SEV-ES VMRUN via host save area
KVM: SVM: Save/restore non-volatile GPRs in SEV-ES VMRUN via host save area
KVM: SVM: Clobber RAX instead of RBX when discarding spec_ctrl_intercepted
KVM: SVM: Drop 32-bit "support" from __svm_sev_es_vcpu_run()
KVM: SVM: Wrap __svm_sev_es_vcpu_run() with #ifdef CONFIG_KVM_AMD_SEV
KVM: SVM: Create a stack frame in __svm_vcpu_run() for unwinding
KVM: SVM: Remove a useless zeroing of allocated memory
...
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Sean Christopherson
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e913ef159f |
KVM: x86: Split core of hypercall emulation to helper function
By necessity, TDX will use a different register ABI for hypercalls. Break out the core functionality so that it may be reused for TDX. Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> Message-Id: <5134caa55ac3dec33fb2addb5545b52b3b52db02.1705965635.git.isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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Paolo Bonzini
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2a955c4db1 |
KVM: x86: Add supported_vm_types to kvm_caps
This simplifies the implementation of KVM_CHECK_EXTENSION(KVM_CAP_VM_TYPES), and also allows the vendor module to specify which VM types are supported. Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-ID: <20240404121327.3107131-9-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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Paolo Bonzini
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517987e3fb |
KVM: x86: add fields to struct kvm_arch for CoCo features
Some VM types have characteristics in common; in fact, the only use of VM types right now is kvm_arch_has_private_mem and it assumes that _all_ nonzero VM types have private memory. We will soon introduce a VM type for SEV and SEV-ES VMs, and at that point we will have two special characteristics of confidential VMs that depend on the VM type: not just if memory is private, but also whether guest state is protected. For the latter we have kvm->arch.guest_state_protected, which is only set on a fully initialized VM. For VM types with protected guest state, we can actually fix a problem in the SEV-ES implementation, where ioctls to set registers do not cause an error even if the VM has been initialized and the guest state encrypted. Make sure that when using VM types that will become an error. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20240209183743.22030-7-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com> Message-ID: <20240404121327.3107131-8-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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Paolo Bonzini
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546d714b08 |
KVM: introduce new vendor op for KVM_GET_DEVICE_ATTR
Allow vendor modules to provide their own attributes on /dev/kvm. To avoid proliferation of vendor ops, implement KVM_HAS_DEVICE_ATTR and KVM_GET_DEVICE_ATTR in terms of the same function. You're not supposed to use KVM_GET_DEVICE_ATTR to do complicated computations, especially on /dev/kvm. Reviewed-by: Michael Roth <michael.roth@amd.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com> Message-ID: <20240404121327.3107131-5-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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Paolo Bonzini
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8d2aec3b2d |
KVM: x86: use u64_to_user_ptr()
There is no danger to the kernel if 32-bit userspace provides a 64-bit value that has the high bits set, but for whatever reason happens to resolve to an address that has something mapped there. KVM uses the checked version of get_user() and put_user(), so any faults are caught properly. Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-ID: <20240404121327.3107131-4-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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Sean Christopherson
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fd706c9b16 |
KVM: x86: Snapshot if a vCPU's vendor model is AMD vs. Intel compatible
Add kvm_vcpu_arch.is_amd_compatible to cache if a vCPU's vendor model is compatible with AMD, i.e. if the vCPU vendor is AMD or Hygon, along with helpers to check if a vCPU is compatible AMD vs. Intel. To handle Intel vs. AMD behavior related to masking the LVTPC entry, KVM will need to check for vendor compatibility on every PMI injection, i.e. querying for AMD will soon be a moderately hot path. Note! This subtly (or maybe not-so-subtly) makes "Intel compatible" KVM's default behavior, both if userspace omits (or never sets) CPUID 0x0 and if userspace sets a completely unknown vendor. One could argue that KVM should treat such vCPUs as not being compatible with Intel *or* AMD, but that would add useless complexity to KVM. KVM needs to do *something* in the face of vendor specific behavior, and so unless KVM conjured up a magic third option, choosing to treat unknown vendors as neither Intel nor AMD means that checks on AMD compatibility would yield Intel behavior, and checks for Intel compatibility would yield AMD behavior. And that's far worse as it would effectively yield random behavior depending on whether KVM checked for AMD vs. Intel vs. !AMD vs. !Intel. And practically speaking, all x86 CPUs follow either Intel or AMD architecture, i.e. "supporting" an unknown third architecture adds no value. Deliberately don't convert any of the existing guest_cpuid_is_intel() checks, as the Intel side of things is messier due to some flows explicitly checking for exactly vendor==Intel, versus some flows assuming anything that isn't "AMD compatible" gets Intel behavior. The Intel code will be cleaned up in the future. Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Message-ID: <20240405235603.1173076-2-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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Li RongQing
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a952d608f0 |
KVM: Use vfree for memory allocated by vcalloc()/__vcalloc()
commit 37b2a6510a48("KVM: use __vcalloc for very large allocations")
replaced kvzalloc()/kvcalloc() with vcalloc(), but didn't replace kvfree()
with vfree().
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Link: https://lore.kernel.org/r/20240131012357.53563-1-lirongqing@baidu.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Daniel Sneddon
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ed2e8d49b5 |
KVM: x86: Add BHI_NO
Intel processors that aren't vulnerable to BHI will set MSR_IA32_ARCH_CAPABILITIES[BHI_NO] = 1;. Guests may use this BHI_NO bit to determine if they need to implement BHI mitigations or not. Allow this bit to be passed to the guests. Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org> |
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Linus Torvalds
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4f712ee0cb |
S390:
* Changes to FPU handling came in via the main s390 pull request
* Only deliver to the guest the SCLP events that userspace has
requested.
* More virtual vs physical address fixes (only a cleanup since
virtual and physical address spaces are currently the same).
* Fix selftests undefined behavior.
x86:
* Fix a restriction that the guest can't program a PMU event whose
encoding matches an architectural event that isn't included in the
guest CPUID. The enumeration of an architectural event only says
that if a CPU supports an architectural event, then the event can be
programmed *using the architectural encoding*. The enumeration does
NOT say anything about the encoding when the CPU doesn't report support
the event *in general*. It might support it, and it might support it
using the same encoding that made it into the architectural PMU spec.
* Fix a variety of bugs in KVM's emulation of RDPMC (more details on
individual commits) and add a selftest to verify KVM correctly emulates
RDMPC, counter availability, and a variety of other PMC-related
behaviors that depend on guest CPUID and therefore are easier to
validate with selftests than with custom guests (aka kvm-unit-tests).
* Zero out PMU state on AMD if the virtual PMU is disabled, it does not
cause any bug but it wastes time in various cases where KVM would check
if a PMC event needs to be synthesized.
* Optimize triggering of emulated events, with a nice ~10% performance
improvement in VM-Exit microbenchmarks when a vPMU is exposed to the
guest.
* Tighten the check for "PMI in guest" to reduce false positives if an NMI
arrives in the host while KVM is handling an IRQ VM-Exit.
* Fix a bug where KVM would report stale/bogus exit qualification information
when exiting to userspace with an internal error exit code.
* Add a VMX flag in /proc/cpuinfo to report 5-level EPT support.
* Rework TDP MMU root unload, free, and alloc to run with mmu_lock held for
read, e.g. to avoid serializing vCPUs when userspace deletes a memslot.
* Tear down TDP MMU page tables at 4KiB granularity (used to be 1GiB). KVM
doesn't support yielding in the middle of processing a zap, and 1GiB
granularity resulted in multi-millisecond lags that are quite impolite
for CONFIG_PREEMPT kernels.
* Allocate write-tracking metadata on-demand to avoid the memory overhead when
a kernel is built with i915 virtualization support but the workloads use
neither shadow paging nor i915 virtualization.
* Explicitly initialize a variety of on-stack variables in the emulator that
triggered KMSAN false positives.
* Fix the debugregs ABI for 32-bit KVM.
* Rework the "force immediate exit" code so that vendor code ultimately decides
how and when to force the exit, which allowed some optimization for both
Intel and AMD.
* Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
vCPU creation ultimately failed, causing extra unnecessary work.
* Cleanup the logic for checking if the currently loaded vCPU is in-kernel.
* Harden against underflowing the active mmu_notifier invalidation
count, so that "bad" invalidations (usually due to bugs elsehwere in the
kernel) are detected earlier and are less likely to hang the kernel.
x86 Xen emulation:
* Overlay pages can now be cached based on host virtual address,
instead of guest physical addresses. This removes the need to
reconfigure and invalidate the cache if the guest changes the
gpa but the underlying host virtual address remains the same.
* When possible, use a single host TSC value when computing the deadline for
Xen timers in order to improve the accuracy of the timer emulation.
* Inject pending upcall events when the vCPU software-enables its APIC to fix
a bug where an upcall can be lost (and to follow Xen's behavior).
* Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen
events fails, e.g. if the guest has aliased xAPIC IDs.
RISC-V:
* Support exception and interrupt handling in selftests
* New self test for RISC-V architectural timer (Sstc extension)
* New extension support (Ztso, Zacas)
* Support userspace emulation of random number seed CSRs.
ARM:
* Infrastructure for building KVM's trap configuration based on the
architectural features (or lack thereof) advertised in the VM's ID
registers
* Support for mapping vfio-pci BARs as Normal-NC (vaguely similar to
x86's WC) at stage-2, improving the performance of interacting with
assigned devices that can tolerate it
* Conversion of KVM's representation of LPIs to an xarray, utilized to
address serialization some of the serialization on the LPI injection
path
* Support for _architectural_ VHE-only systems, advertised through the
absence of FEAT_E2H0 in the CPU's ID register
* Miscellaneous cleanups, fixes, and spelling corrections to KVM and
selftests
LoongArch:
* Set reserved bits as zero in CPUCFG.
* Start SW timer only when vcpu is blocking.
* Do not restart SW timer when it is expired.
* Remove unnecessary CSR register saving during enter guest.
* Misc cleanups and fixes as usual.
Generic:
* cleanup Kconfig by removing CONFIG_HAVE_KVM, which was basically always
true on all architectures except MIPS (where Kconfig determines the
available depending on CPU capabilities). It is replaced either by
an architecture-dependent symbol for MIPS, and IS_ENABLED(CONFIG_KVM)
everywhere else.
* Factor common "select" statements in common code instead of requiring
each architecture to specify it
* Remove thoroughly obsolete APIs from the uapi headers.
* Move architecture-dependent stuff to uapi/asm/kvm.h
* Always flush the async page fault workqueue when a work item is being
removed, especially during vCPU destruction, to ensure that there are no
workers running in KVM code when all references to KVM-the-module are gone,
i.e. to prevent a very unlikely use-after-free if kvm.ko is unloaded.
* Grab a reference to the VM's mm_struct in the async #PF worker itself instead
of gifting the worker a reference, so that there's no need to remember
to *conditionally* clean up after the worker.
Selftests:
* Reduce boilerplate especially when utilize selftest TAP infrastructure.
* Add basic smoke tests for SEV and SEV-ES, along with a pile of library
support for handling private/encrypted/protected memory.
* Fix benign bugs where tests neglect to close() guest_memfd files.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm updates from Paolo Bonzini:
"S390:
- Changes to FPU handling came in via the main s390 pull request
- Only deliver to the guest the SCLP events that userspace has
requested
- More virtual vs physical address fixes (only a cleanup since
virtual and physical address spaces are currently the same)
- Fix selftests undefined behavior
x86:
- Fix a restriction that the guest can't program a PMU event whose
encoding matches an architectural event that isn't included in the
guest CPUID. The enumeration of an architectural event only says
that if a CPU supports an architectural event, then the event can
be programmed *using the architectural encoding*. The enumeration
does NOT say anything about the encoding when the CPU doesn't
report support the event *in general*. It might support it, and it
might support it using the same encoding that made it into the
architectural PMU spec
- Fix a variety of bugs in KVM's emulation of RDPMC (more details on
individual commits) and add a selftest to verify KVM correctly
emulates RDMPC, counter availability, and a variety of other
PMC-related behaviors that depend on guest CPUID and therefore are
easier to validate with selftests than with custom guests (aka
kvm-unit-tests)
- Zero out PMU state on AMD if the virtual PMU is disabled, it does
not cause any bug but it wastes time in various cases where KVM
would check if a PMC event needs to be synthesized
- Optimize triggering of emulated events, with a nice ~10%
performance improvement in VM-Exit microbenchmarks when a vPMU is
exposed to the guest
- Tighten the check for "PMI in guest" to reduce false positives if
an NMI arrives in the host while KVM is handling an IRQ VM-Exit
- Fix a bug where KVM would report stale/bogus exit qualification
information when exiting to userspace with an internal error exit
code
- Add a VMX flag in /proc/cpuinfo to report 5-level EPT support
- Rework TDP MMU root unload, free, and alloc to run with mmu_lock
held for read, e.g. to avoid serializing vCPUs when userspace
deletes a memslot
- Tear down TDP MMU page tables at 4KiB granularity (used to be
1GiB). KVM doesn't support yielding in the middle of processing a
zap, and 1GiB granularity resulted in multi-millisecond lags that
are quite impolite for CONFIG_PREEMPT kernels
- Allocate write-tracking metadata on-demand to avoid the memory
overhead when a kernel is built with i915 virtualization support
but the workloads use neither shadow paging nor i915 virtualization
- Explicitly initialize a variety of on-stack variables in the
emulator that triggered KMSAN false positives
- Fix the debugregs ABI for 32-bit KVM
- Rework the "force immediate exit" code so that vendor code
ultimately decides how and when to force the exit, which allowed
some optimization for both Intel and AMD
- Fix a long-standing bug where kvm_has_noapic_vcpu could be left
elevated if vCPU creation ultimately failed, causing extra
unnecessary work
- Cleanup the logic for checking if the currently loaded vCPU is
in-kernel
- Harden against underflowing the active mmu_notifier invalidation
count, so that "bad" invalidations (usually due to bugs elsehwere
in the kernel) are detected earlier and are less likely to hang the
kernel
x86 Xen emulation:
- Overlay pages can now be cached based on host virtual address,
instead of guest physical addresses. This removes the need to
reconfigure and invalidate the cache if the guest changes the gpa
but the underlying host virtual address remains the same
- When possible, use a single host TSC value when computing the
deadline for Xen timers in order to improve the accuracy of the
timer emulation
- Inject pending upcall events when the vCPU software-enables its
APIC to fix a bug where an upcall can be lost (and to follow Xen's
behavior)
- Fall back to the slow path instead of warning if "fast" IRQ
delivery of Xen events fails, e.g. if the guest has aliased xAPIC
IDs
RISC-V:
- Support exception and interrupt handling in selftests
- New self test for RISC-V architectural timer (Sstc extension)
- New extension support (Ztso, Zacas)
- Support userspace emulation of random number seed CSRs
ARM:
- Infrastructure for building KVM's trap configuration based on the
architectural features (or lack thereof) advertised in the VM's ID
registers
- Support for mapping vfio-pci BARs as Normal-NC (vaguely similar to
x86's WC) at stage-2, improving the performance of interacting with
assigned devices that can tolerate it
- Conversion of KVM's representation of LPIs to an xarray, utilized
to address serialization some of the serialization on the LPI
injection path
- Support for _architectural_ VHE-only systems, advertised through
the absence of FEAT_E2H0 in the CPU's ID register
- Miscellaneous cleanups, fixes, and spelling corrections to KVM and
selftests
LoongArch:
- Set reserved bits as zero in CPUCFG
- Start SW timer only when vcpu is blocking
- Do not restart SW timer when it is expired
- Remove unnecessary CSR register saving during enter guest
- Misc cleanups and fixes as usual
Generic:
- Clean up Kconfig by removing CONFIG_HAVE_KVM, which was basically
always true on all architectures except MIPS (where Kconfig
determines the available depending on CPU capabilities). It is
replaced either by an architecture-dependent symbol for MIPS, and
IS_ENABLED(CONFIG_KVM) everywhere else
- Factor common "select" statements in common code instead of
requiring each architecture to specify it
- Remove thoroughly obsolete APIs from the uapi headers
- Move architecture-dependent stuff to uapi/asm/kvm.h
- Always flush the async page fault workqueue when a work item is
being removed, especially during vCPU destruction, to ensure that
there are no workers running in KVM code when all references to
KVM-the-module are gone, i.e. to prevent a very unlikely
use-after-free if kvm.ko is unloaded
- Grab a reference to the VM's mm_struct in the async #PF worker
itself instead of gifting the worker a reference, so that there's
no need to remember to *conditionally* clean up after the worker
Selftests:
- Reduce boilerplate especially when utilize selftest TAP
infrastructure
- Add basic smoke tests for SEV and SEV-ES, along with a pile of
library support for handling private/encrypted/protected memory
- Fix benign bugs where tests neglect to close() guest_memfd files"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (246 commits)
selftests: kvm: remove meaningless assignments in Makefiles
KVM: riscv: selftests: Add Zacas extension to get-reg-list test
RISC-V: KVM: Allow Zacas extension for Guest/VM
KVM: riscv: selftests: Add Ztso extension to get-reg-list test
RISC-V: KVM: Allow Ztso extension for Guest/VM
RISC-V: KVM: Forward SEED CSR access to user space
KVM: riscv: selftests: Add sstc timer test
KVM: riscv: selftests: Change vcpu_has_ext to a common function
KVM: riscv: selftests: Add guest helper to get vcpu id
KVM: riscv: selftests: Add exception handling support
LoongArch: KVM: Remove unnecessary CSR register saving during enter guest
LoongArch: KVM: Do not restart SW timer when it is expired
LoongArch: KVM: Start SW timer only when vcpu is blocking
LoongArch: KVM: Set reserved bits as zero in CPUCFG
KVM: selftests: Explicitly close guest_memfd files in some gmem tests
KVM: x86/xen: fix recursive deadlock in timer injection
KVM: pfncache: simplify locking and make more self-contained
KVM: x86/xen: remove WARN_ON_ONCE() with false positives in evtchn delivery
KVM: x86/xen: inject vCPU upcall vector when local APIC is enabled
KVM: x86/xen: improve accuracy of Xen timers
...
|
|
|
Linus Torvalds
|
0e33cf955f |
* Mitigate RFDS vulnerability
-----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEV76QKkVc4xCGURexaDWVMHDJkrAFAmXvZgoACgkQaDWVMHDJ krC2Eg//aZKBp97/DSzRqXKDwJzVUr0sGJ9cii0gVT1sI+1U6ZZCh/roVH4xOT5/ HqtOOnQ+X0mwUx2VG3Yv2VPI7VW68sJ3/y9D8R4tnMEsyQ4CmDw96Pre3NyKr/Av jmW7SK94fOkpNFJOMk3zpk7GtRUlCsVkS1P61dOmMYduguhel/V20rWlx83BgnAY Rf/c3rBjqe8Ri3rzBP5icY/d6OgwoafuhME31DD/j6oKOh+EoQBvA4urj46yMTMX /mrK7hCm/wqwuOOvgGbo7sfZNBLCYy3SZ3EyF4beDERhPF1DaSvCwOULpGVJroqu SelFsKXAtEbYrDgsan+MYlx3bQv43q7PbHska1gjkH91plO4nAsssPr5VsusUKmT sq8jyBaauZb40oLOSgooL4RqAHrfs8q5695Ouwh/DB/XovMezUI1N/BkpGFmqpJI o2xH9P5q520pkB8pFhN9TbRuFSGe/dbWC24QTq1DUajo3M3RwcwX6ua9hoAKLtDF pCV5DNcVcXHD3Cxp0M5dQ5JEAiCnW+ZpUWgxPQamGDNW5PEvjDmFwql2uWw/qOuW lkheOIffq8ejUBQFbN8VXfIzzeeKQNFiIcViaqGITjIwhqdHAzVi28OuIGwtdh3g ywLzSC8yvyzgKrNBgtFMr3ucKN0FoPxpBro253xt2H7w8srXW64= =5V9t -----END PGP SIGNATURE----- Merge tag 'rfds-for-linus-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 RFDS mitigation from Dave Hansen: "RFDS is a CPU vulnerability that may allow a malicious userspace to infer stale register values from kernel space. Kernel registers can have all kinds of secrets in them so the mitigation is basically to wait until the kernel is about to return to userspace and has user values in the registers. At that point there is little chance of kernel secrets ending up in the registers and the microarchitectural state can be cleared. This leverages some recent robustness fixes for the existing MDS vulnerability. Both MDS and RFDS use the VERW instruction for mitigation" * tag 'rfds-for-linus-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests x86/rfds: Mitigate Register File Data Sampling (RFDS) Documentation/hw-vuln: Add documentation for RFDS x86/mmio: Disable KVM mitigation when X86_FEATURE_CLEAR_CPU_BUF is set |
|
Pawan Gupta
|
2a0180129d |
KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests
Mitigation for RFDS requires RFDS_CLEAR capability which is enumerated by MSR_IA32_ARCH_CAPABILITIES bit 27. If the host has it set, export it to guests so that they can deploy the mitigation. RFDS_NO indicates that the system is not vulnerable to RFDS, export it to guests so that they don't deploy the mitigation unnecessarily. When the host is not affected by X86_BUG_RFDS, but has RFDS_NO=0, synthesize RFDS_NO to the guest. Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> |
|
|
Paolo Bonzini
|
e9a2bba476 |
KVM Xen and pfncache changes for 6.9:
- Rip out the half-baked support for using gfn_to_pfn caches to manage pages
that are "mapped" into guests via physical addresses.
- Add support for using gfn_to_pfn caches with only a host virtual address,
i.e. to bypass the "gfn" stage of the cache. The primary use case is
overlay pages, where the guest may change the gfn used to reference the
overlay page, but the backing hva+pfn remains the same.
- Add an ioctl() to allow mapping Xen's shared_info page using an hva instead
of a gpa, so that userspace doesn't need to reconfigure and invalidate the
cache/mapping if the guest changes the gpa (but userspace keeps the resolved
hva the same).
- When possible, use a single host TSC value when computing the deadline for
Xen timers in order to improve the accuracy of the timer emulation.
- Inject pending upcall events when the vCPU software-enables its APIC to fix
a bug where an upcall can be lost (and to follow Xen's behavior).
- Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen
events fails, e.g. if the guest has aliased xAPIC IDs.
- Extend gfn_to_pfn_cache's mutex to cover (de)activation (in addition to
refresh), and drop a now-redundant acquisition of xen_lock (that was
protecting the shared_info cache) to fix a deadlock due to recursively
acquiring xen_lock.
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Merge tag 'kvm-x86-xen-6.9' of https://github.com/kvm-x86/linux into HEAD
KVM Xen and pfncache changes for 6.9:
- Rip out the half-baked support for using gfn_to_pfn caches to manage pages
that are "mapped" into guests via physical addresses.
- Add support for using gfn_to_pfn caches with only a host virtual address,
i.e. to bypass the "gfn" stage of the cache. The primary use case is
overlay pages, where the guest may change the gfn used to reference the
overlay page, but the backing hva+pfn remains the same.
- Add an ioctl() to allow mapping Xen's shared_info page using an hva instead
of a gpa, so that userspace doesn't need to reconfigure and invalidate the
cache/mapping if the guest changes the gpa (but userspace keeps the resolved
hva the same).
- When possible, use a single host TSC value when computing the deadline for
Xen timers in order to improve the accuracy of the timer emulation.
- Inject pending upcall events when the vCPU software-enables its APIC to fix
a bug where an upcall can be lost (and to follow Xen's behavior).
- Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen
events fails, e.g. if the guest has aliased xAPIC IDs.
- Extend gfn_to_pfn_cache's mutex to cover (de)activation (in addition to
refresh), and drop a now-redundant acquisition of xen_lock (that was
protecting the shared_info cache) to fix a deadlock due to recursively
acquiring xen_lock.
|
|
|
Paolo Bonzini
|
e9025cdd8c |
KVM x86 PMU changes for 6.9:
- Fix several bugs where KVM speciously prevents the guest from utilizing
fixed counters and architectural event encodings based on whether or not
guest CPUID reports support for the _architectural_ encoding.
- Fix a variety of bugs in KVM's emulation of RDPMC, e.g. for "fast" reads,
priority of VMX interception vs #GP, PMC types in architectural PMUs, etc.
- Add a selftest to verify KVM correctly emulates RDMPC, counter availability,
and a variety of other PMC-related behaviors that depend on guest CPUID,
i.e. are difficult to validate via KVM-Unit-Tests.
- Zero out PMU metadata on AMD if the virtual PMU is disabled to avoid wasting
cycles, e.g. when checking if a PMC event needs to be synthesized when
skipping an instruction.
- Optimize triggering of emulated events, e.g. for "count instructions" events
when skipping an instruction, which yields a ~10% performance improvement in
VM-Exit microbenchmarks when a vPMU is exposed to the guest.
- Tighten the check for "PMI in guest" to reduce false positives if an NMI
arrives in the host while KVM is handling an IRQ VM-Exit.
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Merge tag 'kvm-x86-pmu-6.9' of https://github.com/kvm-x86/linux into HEAD
KVM x86 PMU changes for 6.9:
- Fix several bugs where KVM speciously prevents the guest from utilizing
fixed counters and architectural event encodings based on whether or not
guest CPUID reports support for the _architectural_ encoding.
- Fix a variety of bugs in KVM's emulation of RDPMC, e.g. for "fast" reads,
priority of VMX interception vs #GP, PMC types in architectural PMUs, etc.
- Add a selftest to verify KVM correctly emulates RDMPC, counter availability,
and a variety of other PMC-related behaviors that depend on guest CPUID,
i.e. are difficult to validate via KVM-Unit-Tests.
- Zero out PMU metadata on AMD if the virtual PMU is disabled to avoid wasting
cycles, e.g. when checking if a PMC event needs to be synthesized when
skipping an instruction.
- Optimize triggering of emulated events, e.g. for "count instructions" events
when skipping an instruction, which yields a ~10% performance improvement in
VM-Exit microbenchmarks when a vPMU is exposed to the guest.
- Tighten the check for "PMI in guest" to reduce false positives if an NMI
arrives in the host while KVM is handling an IRQ VM-Exit.
|
|
|
Paolo Bonzini
|
41ebae2ecd |
KVM x86 MMU changes for 6.9:
- Clean up code related to unprotecting shadow pages when retrying a guest
instruction after failed #PF-induced emulation.
- Zap TDP MMU roots at 4KiB granularity to minimize the delay in yielding if
a reschedule is needed, e.g. if a high priority task needs to run. Because
KVM doesn't support yielding in the middle of processing a zapped non-leaf
SPTE, zapping at 1GiB granularity can result in multi-millisecond lag when
attempting to schedule in a high priority.
- Rework TDP MMU root unload, free, and alloc to run with mmu_lock held for
read, e.g. to avoid serializing vCPUs when userspace deletes a memslot.
- Allocate write-tracking metadata on-demand to avoid the memory overhead when
running kernels built with KVMGT support (external write-tracking enabled),
but for workloads that don't use nested virtualization (shadow paging) or
KVMGT.
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Merge tag 'kvm-x86-mmu-6.9' of https://github.com/kvm-x86/linux into HEAD
KVM x86 MMU changes for 6.9:
- Clean up code related to unprotecting shadow pages when retrying a guest
instruction after failed #PF-induced emulation.
- Zap TDP MMU roots at 4KiB granularity to minimize the delay in yielding if
a reschedule is needed, e.g. if a high priority task needs to run. Because
KVM doesn't support yielding in the middle of processing a zapped non-leaf
SPTE, zapping at 1GiB granularity can result in multi-millisecond lag when
attempting to schedule in a high priority.
- Rework TDP MMU root unload, free, and alloc to run with mmu_lock held for
read, e.g. to avoid serializing vCPUs when userspace deletes a memslot.
- Allocate write-tracking metadata on-demand to avoid the memory overhead when
running kernels built with KVMGT support (external write-tracking enabled),
but for workloads that don't use nested virtualization (shadow paging) or
KVMGT.
|
|
|
Paolo Bonzini
|
c9cd0beae9 |
KVM x86 misc changes for 6.9:
- Explicitly initialize a variety of on-stack variables in the emulator that
triggered KMSAN false positives (though in fairness in KMSAN, it's comically
difficult to see that the uninitialized memory is never truly consumed).
- Fix the deubgregs ABI for 32-bit KVM, and clean up code related to reading
DR6 and DR7.
- Rework the "force immediate exit" code so that vendor code ultimately
decides how and when to force the exit. This allows VMX to further optimize
handling preemption timer exits, and allows SVM to avoid sending a duplicate
IPI (SVM also has a need to force an exit).
- Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
vCPU creation ultimately failed, and add WARN to guard against similar bugs.
- Provide a dedicated arch hook for checking if a different vCPU was in-kernel
(for directed yield), and simplify the logic for checking if the currently
loaded vCPU is in-kernel.
- Misc cleanups and fixes.
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Merge tag 'kvm-x86-misc-6.9' of https://github.com/kvm-x86/linux into HEAD
KVM x86 misc changes for 6.9:
- Explicitly initialize a variety of on-stack variables in the emulator that
triggered KMSAN false positives (though in fairness in KMSAN, it's comically
difficult to see that the uninitialized memory is never truly consumed).
- Fix the deubgregs ABI for 32-bit KVM, and clean up code related to reading
DR6 and DR7.
- Rework the "force immediate exit" code so that vendor code ultimately
decides how and when to force the exit. This allows VMX to further optimize
handling preemption timer exits, and allows SVM to avoid sending a duplicate
IPI (SVM also has a need to force an exit).
- Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
vCPU creation ultimately failed, and add WARN to guard against similar bugs.
- Provide a dedicated arch hook for checking if a different vCPU was in-kernel
(for directed yield), and simplify the logic for checking if the currently
loaded vCPU is in-kernel.
- Misc cleanups and fixes.
|
|
|
Paolo Bonzini
|
39fee313fd |
Merge tag 'kvm-x86-guest_memfd_fixes-6.8' of https://github.com/kvm-x86/linux into HEAD
KVM GUEST_MEMFD fixes for 6.8: - Make KVM_MEM_GUEST_MEMFD mutually exclusive with KVM_MEM_READONLY to avoid creating ABI that KVM can't sanely support. - Update documentation for KVM_SW_PROTECTED_VM to make it abundantly clear that such VMs are purely a development and testing vehicle, and come with zero guarantees. - Limit KVM_SW_PROTECTED_VM guests to the TDP MMU, as the long term plan is to support confidential VMs with deterministic private memory (SNP and TDX) only in the TDP MMU. - Fix a bug in a GUEST_MEMFD negative test that resulted in false passes when verifying that KVM_MEM_GUEST_MEMFD memslots can't be dirty logged. |
|
David Woodhouse
|
451a707813 |
KVM: x86/xen: improve accuracy of Xen timers
A test program such as http://david.woodhou.se/timerlat.c confirms user
reports that timers are increasingly inaccurate as the lifetime of a
guest increases. Reporting the actual delay observed when asking for
100µs of sleep, it starts off OK on a newly-launched guest but gets
worse over time, giving incorrect sleep times:
root@ip-10-0-193-21:~# ./timerlat -c -n 5
00000000 latency 103243/100000 (3.2430%)
00000001 latency 103243/100000 (3.2430%)
00000002 latency 103242/100000 (3.2420%)
00000003 latency 103245/100000 (3.2450%)
00000004 latency 103245/100000 (3.2450%)
The biggest problem is that get_kvmclock_ns() returns inaccurate values
when the guest TSC is scaled. The guest sees a TSC value scaled from the
host TSC by a mul/shift conversion (hopefully done in hardware). The
guest then converts that guest TSC value into nanoseconds using the
mul/shift conversion given to it by the KVM pvclock information.
But get_kvmclock_ns() performs only a single conversion directly from
host TSC to nanoseconds, giving a different result. A test program at
http://david.woodhou.se/tsdrift.c demonstrates the cumulative error
over a day.
It's non-trivial to fix get_kvmclock_ns(), although I'll come back to
that. The actual guest hv_clock is per-CPU, and *theoretically* each
vCPU could be running at a *different* frequency. But this patch is
needed anyway because...
The other issue with Xen timers was that the code would snapshot the
host CLOCK_MONOTONIC at some point in time, and then... after a few
interrupts may have occurred, some preemption perhaps... would also read
the guest's kvmclock. Then it would proceed under the false assumption
that those two happened at the *same* time. Any time which *actually*
elapsed between reading the two clocks was introduced as inaccuracies
in the time at which the timer fired.
Fix it to use a variant of kvm_get_time_and_clockread(), which reads the
host TSC just *once*, then use the returned TSC value to calculate the
kvmclock (making sure to do that the way the guest would instead of
making the same mistake get_kvmclock_ns() does).
Sadly, hrtimers based on CLOCK_MONOTONIC_RAW are not supported, so Xen
timers still have to use CLOCK_MONOTONIC. In practice the difference
between the two won't matter over the timescales involved, as the
*absolute* values don't matter; just the delta.
This does mean a new variant of kvm_get_time_and_clockread() is needed;
called kvm_get_monotonic_and_clockread() because that's what it does.
Fixes:
|
|
|
Sean Christopherson
|
a1176ef5c9 |
KVM: x86/mmu: Restrict KVM_SW_PROTECTED_VM to the TDP MMU
Advertise and support software-protected VMs if and only if the TDP MMU is
enabled, i.e. disallow KVM_SW_PROTECTED_VM if TDP is enabled for KVM's
legacy/shadow MMU. TDP support for the shadow MMU is maintenance-only,
e.g. support for TDX and SNP will also be restricted to the TDP MMU.
Fixes:
|
|
|
Sean Christopherson
|
322d79f1db |
KVM: x86: Clean up directed yield API for "has pending interrupt"
Directly return the boolean result of whether or not a vCPU has a pending interrupt instead of effectively doing: if (true) return true; return false; Reviewed-by: Yuan Yao <yuan.yao@intel.com> Link: https://lore.kernel.org/r/20240110003938.490206-4-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
9b8615c5d3 |
KVM: x86: Rely solely on preempted_in_kernel flag for directed yield
Snapshot preempted_in_kernel using kvm_arch_vcpu_in_kernel() so that the flag is "accurate" (or rather, consistent and deterministic within KVM) for guests with protected state, and explicitly use preempted_in_kernel when checking if a vCPU was preempted in kernel mode instead of bouncing through kvm_arch_vcpu_in_kernel(). Drop the gnarly logic in kvm_arch_vcpu_in_kernel() that redirects to preempted_in_kernel if the target vCPU is not the "running", i.e. loaded, vCPU, as the only reason that code existed was for the directed yield case where KVM wants to check the CPL of a vCPU that may or may not be loaded on the current pCPU. Cc: Like Xu <like.xu.linux@gmail.com> Reviewed-by: Yuan Yao <yuan.yao@intel.com> Link: https://lore.kernel.org/r/20240110003938.490206-3-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
77bcd9e623 |
KVM: Add dedicated arch hook for querying if vCPU was preempted in-kernel
Plumb in a dedicated hook for querying whether or not a vCPU was preempted in-kernel. Unlike literally every other architecture, x86's VMX can check if a vCPU is in kernel context if and only if the vCPU is loaded on the current pCPU. x86's kvm_arch_vcpu_in_kernel() works around the limitation by querying kvm_get_running_vcpu() and redirecting to vcpu->arch.preempted_in_kernel as needed. But that's unnecessary, confusing, and fragile, e.g. x86 has had at least one bug where KVM incorrectly used a stale preempted_in_kernel. No functional change intended. Reviewed-by: Yuan Yao <yuan.yao@intel.com> Link: https://lore.kernel.org/r/20240110003938.490206-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
fc3c94142b |
KVM: x86: Sanity check that kvm_has_noapic_vcpu is zero at module_exit()
WARN if kvm.ko is unloaded with an elevated kvm_has_noapic_vcpu to guard against incorrect management of the key, e.g. to detect if KVM fails to decrement the key in error paths. Because kvm_has_noapic_vcpu is purely an optimization, in all likelihood KVM could completely botch handling of kvm_has_noapic_vcpu and no one would notice (which is a good argument for deleting the key entirely, but that's a problem for another day). Note, ideally the sanity check would be performance when kvm_usage_count goes to zero, but adding an arch callback just for this sanity check isn't at all worth doing. Link: https://lore.kernel.org/r/20240209222047.394389-3-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
a78d904669 |
KVM: x86: Move "KVM no-APIC vCPU" key management into local APIC code
Move incrementing and decrementing of kvm_has_noapic_vcpu into kvm_create_lapic() and kvm_free_lapic() respectively to fix a benign bug where KVM fails to decrement the count if vCPU creation ultimately fails, e.g. due to a memory allocation failing. Note, the bug is benign as kvm_has_noapic_vcpu is used purely to optimize lapic_in_kernel() checks, and that optimization is quite dubious. That, and practically speaking no setup that cares at all about performance runs with a userspace local APIC. Reported-by: Li RongQing <lirongqing@baidu.com> Cc: Maxim Levitsky <mlevitsk@redhat.com> Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com> Link: https://lore.kernel.org/r/20240209222047.394389-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
0ec3d6d1f1 |
KVM: x86: Fully defer to vendor code to decide how to force immediate exit
Now that vmx->req_immediate_exit is used only in the scope of vmx_vcpu_run(), use force_immediate_exit to detect that KVM should usurp the VMX preemption to force a VM-Exit and let vendor code fully handle forcing a VM-Exit. Opportunsitically drop __kvm_request_immediate_exit() and just have vendor code call smp_send_reschedule() directly. SVM already does this when injecting an event while also trying to single-step an IRET, i.e. it's not exactly secret knowledge that KVM uses a reschedule IPI to force an exit. Link: https://lore.kernel.org/r/20240110012705.506918-7-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
9c9025ea00 |
KVM: x86: Plumb "force_immediate_exit" into kvm_entry() tracepoint
Annotate the kvm_entry() tracepoint with "immediate exit" when KVM is forcing a VM-Exit immediately after VM-Enter, e.g. when KVM wants to inject an event but needs to first complete some other operation. Knowing that KVM is (or isn't) forcing an exit is useful information when debugging issues related to event injection. Suggested-by: Maxim Levitsky <mlevitsk@redhat.com> Link: https://lore.kernel.org/r/20240110012705.506918-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
dfeef3d3f3 |
KVM: x86: Drop superfluous check on direct MMU vs. WRITE_PF_TO_SP flag
Remove reexecute_instruction()'s final check on the MMU being direct, as
EMULTYPE_WRITE_PF_TO_SP is only ever set if the MMU is indirect, i.e. is a
shadow MMU. Prior to commit
|
|
|
Sean Christopherson
|
515c18a64e |
KVM: x86: Drop dedicated logic for direct MMUs in reexecute_instruction()
Now that KVM doesn't pointlessly acquire mmu_lock for direct MMUs, drop the dedicated path entirely and always query indirect_shadow_pages when deciding whether or not to try unprotecting the gfn. For indirect, a.k.a. shadow MMUs, checking indirect_shadow_pages is harmless; unless *every* shadow page was somehow zapped while KVM was attempting to emulate the instruction, indirect_shadow_pages is guaranteed to be non-zero. Well, unless the instruction used a direct hugepage with 2-level paging for its code page, but in that case, there's obviously nothing to unprotect. And in the extremely unlikely case all shadow pages were zapped, there's again obviously nothing to unprotect. Link: https://lore.kernel.org/r/20240203002343.383056-3-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
Mingwei Zhang
|
474b99ed70 |
KVM: x86/mmu: Don't acquire mmu_lock when using indirect_shadow_pages as a heuristic
Drop KVM's completely pointless acquisition of mmu_lock when deciding whether or not to unprotect any shadow pages residing at the gfn before resuming the guest to let it retry an instruction that KVM failed to emulated. In this case, indirect_shadow_pages is used as a coarse-grained heuristic to check if there is any chance of there being a relevant shadow page to unprotected. But acquiring mmu_lock largely defeats any benefit to the heuristic, as taking mmu_lock for write is likely far more costly to the VM as a whole than unnecessarily walking mmu_page_hash. Furthermore, the current code is already prone to false negatives and false positives, as it drops mmu_lock before checking the flag and unprotecting shadow pages. And as evidenced by the lack of bug reports, neither false positives nor false negatives are problematic. A false positive simply means that KVM will try to unprotect shadow pages that have already been zapped. And a false negative means that KVM will resume the guest without unprotecting the gfn, i.e. if a shadow page was _just_ created, the vCPU will hit the same page fault and do the whole dance all over again, and detect and unprotect the shadow page the second time around (or not, if something else zaps it first). Reported-by: Jim Mattson <jmattson@google.com> Signed-off-by: Mingwei Zhang <mizhang@google.com> [sean: drop READ_ONCE() and comment change, rewrite changelog] Link: https://lore.kernel.org/r/20240203002343.383056-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
2a5f091ce1 |
KVM: x86: Open code all direct reads to guest DR6 and DR7
Bite the bullet, and open code all direct reads of DR6 and DR7. KVM currently has a mix of open coded accesses and calls to kvm_get_dr(), which is confusing and ugly because there's no rhyme or reason as to why any particular chunk of code uses kvm_get_dr(). The obvious alternative is to force all accesses through kvm_get_dr(), but it's not at all clear that doing so would be a net positive, e.g. even if KVM ends up wanting/needing to force all reads through a common helper, e.g. to play caching games, the cost of reverting this change is likely lower than the ongoing cost of maintaining weird, arbitrary code. No functional change intended. Cc: Mathias Krause <minipli@grsecurity.net> Reviewed-by: Mathias Krause <minipli@grsecurity.net> Link: https://lore.kernel.org/r/20240209220752.388160-3-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
fc5375dd8c |
KVM: x86: Make kvm_get_dr() return a value, not use an out parameter
Convert kvm_get_dr()'s output parameter to a return value, and clean up most of the mess that was created by forcing callers to provide a pointer. No functional change intended. Acked-by: Mathias Krause <minipli@grsecurity.net> Reviewed-by: Mathias Krause <minipli@grsecurity.net> Link: https://lore.kernel.org/r/20240209220752.388160-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
Paul Durrant
|
615451d8cb |
KVM: x86/xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability
Now that all relevant kernel changes and selftests are in place, enable the new capability. Signed-off-by: Paul Durrant <pdurrant@amazon.com> Reviewed-by: David Woodhouse <dwmw@amazon.co.uk> Link: https://lore.kernel.org/r/20240215152916.1158-17-paul@xen.org Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Paul Durrant
|
a4bff3df51 |
KVM: pfncache: remove KVM_GUEST_USES_PFN usage
As noted in [1] the KVM_GUEST_USES_PFN usage flag is never set by any callers of kvm_gpc_init(), and for good reason: the implementation is incomplete/broken. And it's not clear that there will ever be a user of KVM_GUEST_USES_PFN, as coordinating vCPUs with mmu_notifier events is non-trivial. Remove KVM_GUEST_USES_PFN and all related code, e.g. dropping KVM_GUEST_USES_PFN also makes the 'vcpu' argument redundant, to avoid having to reason about broken code as __kvm_gpc_refresh() evolves. Moreover, all existing callers specify KVM_HOST_USES_PFN so the usage check in hva_to_pfn_retry() and hence the 'usage' argument to kvm_gpc_init() are also redundant. [1] https://lore.kernel.org/all/ZQiR8IpqOZrOpzHC@google.com Signed-off-by: Paul Durrant <pdurrant@amazon.com> Reviewed-by: David Woodhouse <dwmw@amazon.co.uk> Link: https://lore.kernel.org/r/20240215152916.1158-6-paul@xen.org [sean: explicitly call out that guest usage is incomplete] Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Paul Durrant
|
78b74638eb |
KVM: pfncache: add a mark-dirty helper
At the moment pages are marked dirty by open-coded calls to mark_page_dirty_in_slot(), directly deferefencing the gpa and memslot from the cache. After a subsequent patch these may not always be set so add a helper now so that caller will protected from the need to know about this detail. Signed-off-by: Paul Durrant <pdurrant@amazon.com> Reviewed-by: David Woodhouse <dwmw@amazon.co.uk> Link: https://lore.kernel.org/r/20240215152916.1158-5-paul@xen.org [sean: decrease indentation, use gpa_to_gfn()] Signed-off-by: Sean Christopherson <seanjc@google.com> |
|
|
Sean Christopherson
|
910c57dfa4 |
KVM: x86: Mark target gfn of emulated atomic instruction as dirty
When emulating an atomic access on behalf of the guest, mark the target
gfn dirty if the CMPXCHG by KVM is attempted and doesn't fault. This
fixes a bug where KVM effectively corrupts guest memory during live
migration by writing to guest memory without informing userspace that the
page is dirty.
Marking the page dirty got unintentionally dropped when KVM's emulated
CMPXCHG was converted to do a user access. Before that, KVM explicitly
mapped the guest page into kernel memory, and marked the page dirty during
the unmap phase.
Mark the page dirty even if the CMPXCHG fails, as the old data is written
back on failure, i.e. the page is still written. The value written is
guaranteed to be the same because the operation is atomic, but KVM's ABI
is that all writes are dirty logged regardless of the value written. And
more importantly, that's what KVM did before the buggy commit.
Huge kudos to the folks on the Cc list (and many others), who did all the
actual work of triaging and debugging.
Fixes:
|
|
|
Paolo Bonzini
|
2f8ebe43a0 |
KVM selftests fixes/cleanups (and one KVM x86 cleanup) for 6.8:
- Remove redundant newlines from error messages.
- Delete an unused variable in the AMX test (which causes build failures when
compiling with -Werror).
- Fail instead of skipping tests if open(), e.g. of /dev/kvm, fails with an
error code other than ENOENT (a Hyper-V selftest bug resulted in an EMFILE,
and the test eventually got skipped).
- Fix TSC related bugs in several Hyper-V selftests.
- Fix a bug in the dirty ring logging test where a sem_post() could be left
pending across multiple runs, resulting in incorrect synchronization between
the main thread and the vCPU worker thread.
- Relax the dirty log split test's assertions on 4KiB mappings to fix false
positives due to the number of mappings for memslot 0 (used for code and
data that is NOT being dirty logged) changing, e.g. due to NUMA balancing.
- Have KVM's gtod_is_based_on_tsc() return "bool" instead of an "int" (the
function generates boolean values, and all callers treat the return value as
a bool).
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Merge tag 'kvm-x86-selftests-6.8-rcN' of https://github.com/kvm-x86/linux into HEAD
KVM selftests fixes/cleanups (and one KVM x86 cleanup) for 6.8:
- Remove redundant newlines from error messages.
- Delete an unused variable in the AMX test (which causes build failures when
compiling with -Werror).
- Fail instead of skipping tests if open(), e.g. of /dev/kvm, fails with an
error code other than ENOENT (a Hyper-V selftest bug resulted in an EMFILE,
and the test eventually got skipped).
- Fix TSC related bugs in several Hyper-V selftests.
- Fix a bug in the dirty ring logging test where a sem_post() could be left
pending across multiple runs, resulting in incorrect synchronization between
the main thread and the vCPU worker thread.
- Relax the dirty log split test's assertions on 4KiB mappings to fix false
positives due to the number of mappings for memslot 0 (used for code and
data that is NOT being dirty logged) changing, e.g. due to NUMA balancing.
- Have KVM's gtod_is_based_on_tsc() return "bool" instead of an "int" (the
function generates boolean values, and all callers treat the return value as
a bool).
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Paolo Bonzini
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22d0bc0721 |
KVM x86 fixes for 6.8:
- Make a KVM_REQ_NMI request while handling KVM_SET_VCPU_EVENTS if and only
if the incoming events->nmi.pending is non-zero. If the target vCPU is in
the UNITIALIZED state, the spurious request will result in KVM exiting to
userspace, which in turn causes QEMU to constantly acquire and release
QEMU's global mutex, to the point where the BSP is unable to make forward
progress.
- Fix a type (u8 versus u64) goof that results in pmu->fixed_ctr_ctrl being
incorrectly truncated, and ultimately causes KVM to think a fixed counter
has already been disabled (KVM thinks the old value is '0').
- Fix a stack leak in KVM_GET_MSRS where a failed MSR read from userspace
that is ultimately ignored due to ignore_msrs=true doesn't zero the output
as intended.
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Merge tag 'kvm-x86-fixes-6.8-rcN' of https://github.com/kvm-x86/linux into HEAD
KVM x86 fixes for 6.8:
- Make a KVM_REQ_NMI request while handling KVM_SET_VCPU_EVENTS if and only
if the incoming events->nmi.pending is non-zero. If the target vCPU is in
the UNITIALIZED state, the spurious request will result in KVM exiting to
userspace, which in turn causes QEMU to constantly acquire and release
QEMU's global mutex, to the point where the BSP is unable to make forward
progress.
- Fix a type (u8 versus u64) goof that results in pmu->fixed_ctr_ctrl being
incorrectly truncated, and ultimately causes KVM to think a fixed counter
has already been disabled (KVM thinks the old value is '0').
- Fix a stack leak in KVM_GET_MSRS where a failed MSR read from userspace
that is ultimately ignored due to ignore_msrs=true doesn't zero the output
as intended.
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Mathias Krause
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e1dda3afe2 |
KVM: x86: Fix broken debugregs ABI for 32 bit kernels
The ioctl()s to get and set KVM's debug registers are broken for 32 bit
kernels as they'd only copy half of the user register state because of a
UAPI and in-kernel type mismatch (__u64 vs. unsigned long; 8 vs. 4
bytes).
This makes it impossible for userland to set anything but DR0 without
resorting to bit folding tricks.
Switch to a loop for copying debug registers that'll implicitly do the
type conversion for us, if needed.
There are likely no users (left) for 32bit KVM, fix the bug nonetheless.
Fixes:
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Mathias Krause
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3376ca3f1a |
KVM: x86: Fix KVM_GET_MSRS stack info leak
Commit |
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Sean Christopherson
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f19063b1ca |
KVM: x86/pmu: Snapshot event selectors that KVM emulates in software
Snapshot the event selectors for the events that KVM emulates in software, which is currently instructions retired and branch instructions retired. The event selectors a tied to the underlying CPU, i.e. are constant for a given platform even though perf doesn't manage the mappings as such. Getting the event selectors from perf isn't exactly cheap, especially if mitigations are enabled, as at least one indirect call is involved. Snapshot the values in KVM instead of optimizing perf as working with the raw event selectors will be required if KVM ever wants to emulate events that aren't part of perf's uABI, i.e. that don't have an "enum perf_hw_id" entry. Link: https://lore.kernel.org/r/20231110022857.1273836-8-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
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Vitaly Kuznetsov
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9e62797fd7 |
KVM: x86: Make gtod_is_based_on_tsc() return 'bool'
gtod_is_based_on_tsc() is boolean in nature, i.e. it returns '1' for good clocksources and '0' otherwise. Moreover, its result is used raw by kvm_get_time_and_clockread()/kvm_get_walltime_and_clockread() which are 'bool'. No functional change intended. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Link: https://lore.kernel.org/r/20240109141121.1619463-6-vkuznets@redhat.com Signed-off-by: Sean Christopherson <seanjc@google.com> |