On 11/6/23 16:45, Lendacky, Thomas via groups.io wrote:
The CPUID_EXTENDED_TOPOLOGY CPUID leaf takes a subleaf as input when returning CPUID information. However, the AsmCpuid() function does not zero out ECX before the CPUID instruction, so the input leaf is used as the sub-leaf for the CPUID request and returns erroneous/invalid CPUID data, since the intent of the request was to get data related to sub-leaf 0. Instead, use AsmCpuidEx() for the CPUID_EXTENDED_TOPOLOGY leaf.
Alternatively, the AsmCpuid() function could be changed to XOR ECX before invoking the CPUID instruction. This would ensure that the 0 sub-leaf is returned for any CPUID leaves that support sub-leaves. Thoughts?
Adding some additional maintainers for their thoughts, too. Thanks, Tom
Fixes: d4d7c9ad5fe5 ("UefiCpuPkg/MpInitLib: use BSP to do extended ...") Signed-off-by: Tom Lendacky <thomas.lenda...@amd.com> --- UefiCpuPkg/Library/MpInitLib/AmdSev.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/UefiCpuPkg/Library/MpInitLib/AmdSev.c b/UefiCpuPkg/Library/MpInitLib/AmdSev.c index bda4960f6fd3..d34f9513e002 100644 --- a/UefiCpuPkg/Library/MpInitLib/AmdSev.c +++ b/UefiCpuPkg/Library/MpInitLib/AmdSev.c @@ -256,7 +256,14 @@ FillExchangeInfoDataSevEs ( if (StdRangeMax >= CPUID_EXTENDED_TOPOLOGY) { CPUID_EXTENDED_TOPOLOGY_EBX ExtTopoEbx;- AsmCpuid (CPUID_EXTENDED_TOPOLOGY, NULL, &ExtTopoEbx.Uint32, NULL, NULL);+ AsmCpuidEx ( + CPUID_EXTENDED_TOPOLOGY, + 0, + NULL, + &ExtTopoEbx.Uint32, + NULL, + NULL + ); ExchangeInfo->ExtTopoAvail = !!ExtTopoEbx.Bits.LogicalProcessors; } }
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