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KVM: arm64: Turn vgic-v3 errata traps into a patched-in constant 

The trap bits are currently only set to manage CPU errata. However,
we are about to make use of them for purposes beyond beating broken
CPUs into submission.

For this purpose, turn these errata-driven bits into a patched-in
constant that is merged with the KVM-driven value at the point of
programming the ICH_HCR_EL2 register, rather than being directly
stored with with the shadow value..

This allows the KVM code to distinguish between a trap being handled
for the purpose of an erratum workaround, or for KVM's own need.

Tested-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://msgid.link/20251120172540.2267180-5-maz@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Marc Zyngier 2025-11-20 17:24:54 +00:00 committed by Oliver Upton
parent 08f4f41c1e
commit 8d3dfab1d3
5 changed files with 84 additions and 49 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm64/kernel/image-vars.h
View File

@ -91,6 +91,7 @@ KVM_NVHE_ALIAS(spectre_bhb_patch_loop_mitigation_enable);
KVM_NVHE_ALIAS(spectre_bhb_patch_wa3);
KVM_NVHE_ALIAS(spectre_bhb_patch_clearbhb);
KVM_NVHE_ALIAS(alt_cb_patch_nops);
KVM_NVHE_ALIAS(kvm_compute_ich_hcr_trap_bits);
/* Global kernel state accessed by nVHE hyp code. */
KVM_NVHE_ALIAS(kvm_vgic_global_state);

21
arch/arm64/kvm/hyp/vgic-v3-sr.c
View File

@ -14,6 +14,8 @@
#include <asm/kvm_hyp.h>
#include <asm/kvm_mmu.h>
#include "../../vgic/vgic.h"
#define vtr_to_max_lr_idx(v) ((v) & 0xf)
#define vtr_to_nr_pre_bits(v) ((((u32)(v) >> 26) & 7) + 1)
#define vtr_to_nr_apr_regs(v) (1 << (vtr_to_nr_pre_bits(v) - 5))
@ -196,6 +198,11 @@ static u32 __vgic_v3_read_ap1rn(int n)
return val;
}
static u64 compute_ich_hcr(struct vgic_v3_cpu_if *cpu_if)
{
return cpu_if->vgic_hcr | vgic_ich_hcr_trap_bits();
}
void __vgic_v3_save_state(struct vgic_v3_cpu_if *cpu_if)
{
u64 used_lrs = cpu_if->used_lrs;
@ -218,7 +225,7 @@ void __vgic_v3_save_state(struct vgic_v3_cpu_if *cpu_if)
elrsr = read_gicreg(ICH_ELRSR_EL2);
write_gicreg(cpu_if->vgic_hcr & ~ICH_HCR_EL2_En, ICH_HCR_EL2);
write_gicreg(0, ICH_HCR_EL2);
for (i = 0; i < used_lrs; i++) {
if (elrsr & (1 << i))
@ -237,7 +244,7 @@ void __vgic_v3_restore_state(struct vgic_v3_cpu_if *cpu_if)
int i;
if (used_lrs || cpu_if->its_vpe.its_vm) {
write_gicreg(cpu_if->vgic_hcr, ICH_HCR_EL2);
write_gicreg(compute_ich_hcr(cpu_if), ICH_HCR_EL2);
for (i = 0; i < used_lrs; i++)
__gic_v3_set_lr(cpu_if->vgic_lr[i], i);
@ -307,14 +314,14 @@ void __vgic_v3_activate_traps(struct vgic_v3_cpu_if *cpu_if)
}
/*
* If we need to trap system registers, we must write
* ICH_HCR_EL2 anyway, even if no interrupts are being
* injected. Note that this also applies if we don't expect
* any system register access (no vgic at all).
* If we need to trap system registers, we must write ICH_HCR_EL2
* anyway, even if no interrupts are being injected. Note that this
* also applies if we don't expect any system register access (no
* vgic at all). In any case, no need to provide MI configuration.
*/
if (static_branch_unlikely(&vgic_v3_cpuif_trap) ||
cpu_if->its_vpe.its_vm || !cpu_if->vgic_sre)
write_gicreg(cpu_if->vgic_hcr, ICH_HCR_EL2);
write_gicreg(vgic_ich_hcr_trap_bits() | ICH_HCR_EL2_En, ICH_HCR_EL2);
}
void __vgic_v3_deactivate_traps(struct vgic_v3_cpu_if *cpu_if)

12
arch/arm64/kvm/vgic/vgic-v3-nested.c
View File

@ -298,19 +298,9 @@ static void vgic_v3_create_shadow_state(struct kvm_vcpu *vcpu,
struct vgic_v3_cpu_if *s_cpu_if)
{
struct vgic_v3_cpu_if *host_if = &vcpu->arch.vgic_cpu.vgic_v3;
u64 val = 0;
int i;
/*
* If we're on a system with a broken vgic that requires
* trapping, propagate the trapping requirements.
*
* Ah, the smell of rotten fruits...
*/
if (static_branch_unlikely(&vgic_v3_cpuif_trap))
val = host_if->vgic_hcr & (ICH_HCR_EL2_TALL0 | ICH_HCR_EL2_TALL1 |
ICH_HCR_EL2_TC | ICH_HCR_EL2_TDIR);
s_cpu_if->vgic_hcr = __vcpu_sys_reg(vcpu, ICH_HCR_EL2) | val;
s_cpu_if->vgic_hcr = __vcpu_sys_reg(vcpu, ICH_HCR_EL2);
s_cpu_if->vgic_vmcr = __vcpu_sys_reg(vcpu, ICH_VMCR_EL2);
s_cpu_if->vgic_sre = host_if->vgic_sre;

83
arch/arm64/kvm/vgic/vgic-v3.c
View File

@ -301,20 +301,9 @@ void vcpu_set_ich_hcr(struct kvm_vcpu *vcpu)
return;
/* Hide GICv3 sysreg if necessary */
if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V2) {
if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V2)
vgic_v3->vgic_hcr |= (ICH_HCR_EL2_TALL0 | ICH_HCR_EL2_TALL1 |
ICH_HCR_EL2_TC);
return;
}
if (group0_trap)
vgic_v3->vgic_hcr |= ICH_HCR_EL2_TALL0;
if (group1_trap)
vgic_v3->vgic_hcr |= ICH_HCR_EL2_TALL1;
if (common_trap)
vgic_v3->vgic_hcr |= ICH_HCR_EL2_TC;
if (dir_trap)
vgic_v3->vgic_hcr |= ICH_HCR_EL2_TDIR;
}
int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq)
@ -635,8 +624,50 @@ static const struct midr_range broken_seis[] = {
static bool vgic_v3_broken_seis(void)
{
return ((kvm_vgic_global_state.ich_vtr_el2 & ICH_VTR_EL2_SEIS) &&
is_midr_in_range_list(broken_seis));
return (is_kernel_in_hyp_mode() &&
is_midr_in_range_list(broken_seis) &&
(read_sysreg_s(SYS_ICH_VTR_EL2) & ICH_VTR_EL2_SEIS));
}
void noinstr kvm_compute_ich_hcr_trap_bits(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr,
int nr_inst)
{
u32 insn, oinsn, rd;
u64 hcr = 0;
if (cpus_have_cap(ARM64_WORKAROUND_CAVIUM_30115)) {
group0_trap = true;
group1_trap = true;
}
if (vgic_v3_broken_seis()) {
/* We know that these machines have ICH_HCR_EL2.TDIR */
group0_trap = true;
group1_trap = true;
dir_trap = true;
}
if (group0_trap)
hcr |= ICH_HCR_EL2_TALL0;
if (group1_trap)
hcr |= ICH_HCR_EL2_TALL1;
if (common_trap)
hcr |= ICH_HCR_EL2_TC;
if (dir_trap)
hcr |= ICH_HCR_EL2_TDIR;
/* Compute target register */
oinsn = le32_to_cpu(*origptr);
rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, oinsn);
/* movz rd, #(val & 0xffff) */
insn = aarch64_insn_gen_movewide(rd,
(u16)hcr,
0,
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_MOVEWIDE_ZERO);
*updptr = cpu_to_le32(insn);
}
/**
@ -650,6 +681,7 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
{
u64 ich_vtr_el2 = kvm_call_hyp_ret(__vgic_v3_get_gic_config);
bool has_v2;
u64 traps;
int ret;
has_v2 = ich_vtr_el2 >> 63;
@ -708,29 +740,18 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
if (has_v2)
static_branch_enable(&vgic_v3_has_v2_compat);
if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_30115)) {
group0_trap = true;
group1_trap = true;
}
if (vgic_v3_broken_seis()) {
kvm_info("GICv3 with broken locally generated SEI\n");
kvm_vgic_global_state.ich_vtr_el2 &= ~ICH_VTR_EL2_SEIS;
group0_trap = true;
group1_trap = true;
if (ich_vtr_el2 & ICH_VTR_EL2_TDS)
dir_trap = true;
else
common_trap = true;
}
if (group0_trap || group1_trap || common_trap | dir_trap) {
traps = vgic_ich_hcr_trap_bits();
if (traps) {
kvm_info("GICv3 sysreg trapping enabled ([%s%s%s%s], reduced performance)\n",
group0_trap ? "G0" : "",
group1_trap ? "G1" : "",
common_trap ? "C" : "",
dir_trap ? "D" : "");
(traps & ICH_HCR_EL2_TALL0) ? "G0" : "",
(traps & ICH_HCR_EL2_TALL1) ? "G1" : "",
(traps & ICH_HCR_EL2_TC) ? "C" : "",
(traps & ICH_HCR_EL2_TDIR) ? "D" : "");
static_branch_enable(&vgic_v3_cpuif_trap);
}

16
arch/arm64/kvm/vgic/vgic.h
View File

@ -164,6 +164,22 @@ static inline int vgic_write_guest_lock(struct kvm *kvm, gpa_t gpa,
return ret;
}
void kvm_compute_ich_hcr_trap_bits(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst);
static inline u64 vgic_ich_hcr_trap_bits(void)
{
u64 hcr;
/* All the traps are in the bottom 16bits */
asm volatile(ALTERNATIVE_CB("movz %0, #0\n",
ARM64_ALWAYS_SYSTEM,
kvm_compute_ich_hcr_trap_bits)
: "=r" (hcr));
return hcr;
}
/*
* This struct provides an intermediate representation of the fields contained
* in the GICH_VMCR and ICH_VMCR registers, such that code exporting the GIC