6.15-stable review patch. If anyone has any objections, please let me know.
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From: Mikhail Paulyshka me@mixaill.net
commit 5b937a1ed64ebeba8876e398110a5790ad77407c upstream.
AMD Cyan Skillfish (Family 17h, Model 47h, Stepping 0h) has an error that causes RDSEED to always return 0xffffffff, while RDRAND works correctly.
Mask the RDSEED cap for this CPU so that both /proc/cpuinfo and direct CPUID read report RDSEED as unavailable.
[ bp: Move to amd.c, massage. ]
Signed-off-by: Mikhail Paulyshka me@mixaill.net Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Cc: stable@kernel.org Link: https://lore.kernel.org/20250524145319.209075-1-me@mixaill.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/msr-index.h | 1 + arch/x86/kernel/cpu/amd.c | 7 +++++++ tools/arch/x86/include/asm/msr-index.h | 1 + 3 files changed, 9 insertions(+)
--- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -624,6 +624,7 @@ #define MSR_AMD64_OSVW_STATUS 0xc0010141 #define MSR_AMD_PPIN_CTL 0xc00102f0 #define MSR_AMD_PPIN 0xc00102f1 +#define MSR_AMD64_CPUID_FN_7 0xc0011002 #define MSR_AMD64_CPUID_FN_1 0xc0011004 #define MSR_AMD64_LS_CFG 0xc0011020 #define MSR_AMD64_DC_CFG 0xc0011022 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -972,6 +972,13 @@ static void init_amd_zen2(struct cpuinfo init_spectral_chicken(c); fix_erratum_1386(c); zen2_zenbleed_check(c); + + /* Disable RDSEED on AMD Cyan Skillfish because of an error. */ + if (c->x86_model == 0x47 && c->x86_stepping == 0x0) { + clear_cpu_cap(c, X86_FEATURE_RDSEED); + msr_clear_bit(MSR_AMD64_CPUID_FN_7, 18); + pr_emerg("RDSEED is not reliable on this platform; disabling.\n"); + } }
static void init_amd_zen3(struct cpuinfo_x86 *c) --- a/tools/arch/x86/include/asm/msr-index.h +++ b/tools/arch/x86/include/asm/msr-index.h @@ -616,6 +616,7 @@ #define MSR_AMD64_OSVW_STATUS 0xc0010141 #define MSR_AMD_PPIN_CTL 0xc00102f0 #define MSR_AMD_PPIN 0xc00102f1 +#define MSR_AMD64_CPUID_FN_7 0xc0011002 #define MSR_AMD64_CPUID_FN_1 0xc0011004 #define MSR_AMD64_LS_CFG 0xc0011020 #define MSR_AMD64_DC_CFG 0xc0011022