x86/amd_nb: Enhance SMN access error checking

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AMD Zen-based systems use a System Management Network (SMN) that
provides access to implementation-specific registers.

SMN accesses are done indirectly through an index/data pair in PCI
config space. The accesses can fail for a variety of reasons.

Include code comments to describe some possible scenarios.

Require error checking for callers of amd_smn_read() and amd_smn_write().
This is needed because many error conditions cannot be checked by these
functions.

  [ bp: Touchup comment. ]

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20240606-fix-smn-bad-read-v4-4-ffde21931c3f@amd.com

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This commit is contained in:

Yazen Ghannam 2024-06-06 11:12:57 -05:00 • committed by Borislav Petkov (AMD)

parent c2d79cc545

commit dc5243921b

2 changed files with 41 additions and 7 deletions

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4

arch/x86/include/asm/amd_nb.h

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44

arch/x86/kernel/amd_nb.c

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