Recent AMD node rework removed the "search and count" method of caching AMD
root devices. This depended on the value from a Data Fabric register that was
expected to hold the PCI bus of one of the root devices attached to that
fabric.
However, this expectation is incorrect. The register, when read from PCI
config space, returns the bitwise-OR of the buses of all attached root
devices.
This behavior is benign on AMD reference design boards, since the bus numbers
are aligned. This results in a bitwise-OR value matching one of the buses. For
example, 0x00 | 0x40 | 0xA0 | 0xE0 = 0xE0.
This behavior breaks on boards where the bus numbers are not exactly aligned.
For example, 0x00 | 0x07 | 0xE0 | 0x15 = 0x1F.
The examples above are for AMD node 0. The first root device on other nodes
will not be 0x00. The first root device for other nodes will depend on the
total number of root devices, the system topology, and the specific PCI bus
number assignment.
For example, a system with 2 AMD nodes could have this:
Node 0 : 0x00 0x07 0x0e 0x15
Node 1 : 0x1c 0x23 0x2a 0x31
The bus numbering style in the reference boards is not a requirement. The
numbering found in other boards is not incorrect. Therefore, the root device
caching method needs to be adjusted.
Go back to the "search and count" method used before the recent rework.
Search for root devices using PCI class code rather than fixed PCI IDs.
This keeps the goal of the rework (remove dependency on PCI IDs) while being
able to support various board designs.
Merge helper functions to reduce code duplication.
[ bp: Reflow comment. ]
Fixes: 40a5f6ffdf ("x86/amd_nb: Simplify root device search")
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/all/20251028-fix-amd-root-v2-1-843e38f8be2c@amd.com
There are certain registers on AMD Zen systems that can only be accessed
through SMN.
Introduce a new interface that provides debugfs files for accessing SMN. As
this introduces the capability for userspace to manipulate the hardware in
unpredictable ways, taint the kernel when writing.
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250130-wip-x86-amd-nb-cleanup-v4-3-b5cc997e471b@amd.com
Offsets 0x60 and 0x64 are used internally by kernel drivers that call
the amd_smn_read() and amd_smn_write() functions. If userspace accesses
the regions at the same time as the kernel it may cause malfunctions in
drivers using the offsets.
Add these offsets to the exclusions so that the kernel is tainted if a
non locked down userspace tries to access them.
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250130-wip-x86-amd-nb-cleanup-v4-2-b5cc997e471b@amd.com
The HSMP interface is just an SMN interface with different offsets.
Define an HSMP wrapper in the SMN code and have the HSMP platform driver
use that rather than a local solution.
Also, remove the "root" member from AMD_NB, since there are no more
users of it.
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Carlos Bilbao <carlos.bilbao@kernel.org>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20250130-wip-x86-amd-nb-cleanup-v4-1-b5cc997e471b@amd.com
There are more than one SMN index/data pair available for software use.
The register offsets are different, but the protocol is the same.
Use defines for the SMN offset values and allow the index/data offsets
to be passed to the read/write helper function.
This eases code reuse with other SMN users in the kernel.
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241206161210.163701-14-yazen.ghannam@amd.com
Use guard(mutex) and convert PCI error codes to common ones.
Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241206161210.163701-12-yazen.ghannam@amd.com
SMN access was bolted into amd_nb mostly as convenience. This has
limitations though that require incurring tech debt to keep it working.
Move SMN access to the newly introduced AMD Node driver.
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> # pdx86
Acked-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com> # PMF, PMC
Link: https://lore.kernel.org/r/20241206161210.163701-11-yazen.ghannam@amd.com
The "root" device search was introduced to support SMN access for Zen
systems. This device represents a PCIe root complex. It is not the
same as the "CPU/node" devices found at slots 0x18-0x1F.
There may be multiple PCIe root complexes within an AMD node. Such is
the case with server or High-end Desktop (HEDT) systems, etc. Therefore
it is not enough to assume "root <-> AMD node" is a 1-to-1 association.
Currently, this is handled by skipping "extra" root complexes during the
search. However, the hardware provides the PCI bus number of an AMD
node's root device.
Use the hardware info to get the root device's bus and drop the extra
search code and PCI IDs.
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241206161210.163701-7-yazen.ghannam@amd.com
The "AMD Node" concept spans many families of systems and applies to
a number of subsystems and drivers.
Currently, the AMD Northbridge code is overloaded with AMD node
functionality. However, the node concept is broader than just
northbridges.
Start files to host common AMD node functions and definitions. Include
a helper to find an AMD node device function based on the convention
described in AMD documentation.
Anything that needs node functionality should include this rather than
amd_nb.h. The AMD_NB code will be reduced to only northbridge-specific
code needed for legacy systems.
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241206161210.163701-5-yazen.ghannam@amd.com
Yazen Ghannam
Ingo Molnar
Mario Limonciello