diff options
| author | Gregory Price <gourry@gourry.net> | 2025-10-20 11:13:55 +0200 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2025-10-28 12:37:49 +0100 |
| commit | 607b9fb2ce248cc5b633c5949e0153838992c152 (patch) | |
| tree | 07af746f4fcdd0eca790152340e661ea532cfc65 | |
| parent | 8a9fb5129e8e64d24543ebc70de941a2d77a9e77 (diff) | |
x86/CPU/AMD: Add RDSEED fix for Zen5
There's an issue with RDSEED's 16-bit and 32-bit register output
variants on Zen5 which return a random value of 0 "at a rate inconsistent
with randomness while incorrectly signaling success (CF=1)". Search the
web for AMD-SB-7055 for more detail.
Add a fix glue which checks microcode revisions.
[ bp: Add microcode revisions checking, rewrite. ]
Cc: stable@vger.kernel.org
Signed-off-by: Gregory Price <gourry@gourry.net>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20251018024010.4112396-1-gourry@gourry.net
| -rw-r--r-- | arch/x86/kernel/cpu/amd.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index ccaa51ce63f6..bc29be670a2a 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -1035,8 +1035,18 @@ static void init_amd_zen4(struct cpuinfo_x86 *c) } } +static const struct x86_cpu_id zen5_rdseed_microcode[] = { + ZEN_MODEL_STEP_UCODE(0x1a, 0x02, 0x1, 0x0b00215a), + ZEN_MODEL_STEP_UCODE(0x1a, 0x11, 0x0, 0x0b101054), +}; + static void init_amd_zen5(struct cpuinfo_x86 *c) { + if (!x86_match_min_microcode_rev(zen5_rdseed_microcode)) { + clear_cpu_cap(c, X86_FEATURE_RDSEED); + msr_clear_bit(MSR_AMD64_CPUID_FN_7, 18); + pr_emerg_once("RDSEED32 is broken. Disabling the corresponding CPUID bit.\n"); + } } static void init_amd(struct cpuinfo_x86 *c) |