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From: "Lendacky, Thomas via groups.io" <thomas.lendacky=amd.com@groups.io>
To: devel@edk2.groups.io, "Kinney,
	Michael D" <michael.d.kinney@intel.com>,
	"Gao, Liming" <liming.gao@intel.com>,
	"Liu, Zhiguang" <zhiguang.liu@intel.com>
Cc: Eric Dong <eric.dong@intel.com>, Ray Ni <ray.ni@intel.com>,
	Rahul Kumar <rahul1.kumar@intel.com>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Ard Biesheuvel <ardb+tianocore@kernel.org>,
	Michael Roth <michael.roth@amd.com>
Subject: Re: [edk2-devel] [PATCH 1/2] UefiCpuPkg/MpInitLib: Use AsmCpuidEx() for CPUID_EXTENDED_TOPOLOGY leaf
Date: Mon, 6 Nov 2023 17:15:51 -0600	[thread overview]
Message-ID: <26becea4-2ad8-4773-ab3d-5ad98ff48759@amd.com> (raw)
In-Reply-To: <17952A20A9E21541.12603@groups.io>

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.lendacky@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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  parent reply	other threads:[~2023-11-06 23:15 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-06 22:45 [edk2-devel] [PATCH 0/2] SEV-SNP guest support fixes Lendacky, Thomas via groups.io
2023-11-06 22:45 ` [edk2-devel] [PATCH 1/2] UefiCpuPkg/MpInitLib: Use AsmCpuidEx() for CPUID_EXTENDED_TOPOLOGY leaf Lendacky, Thomas via groups.io
2023-11-28 10:31   ` Ni, Ray
2023-11-06 22:45 ` [edk2-devel] [PATCH 2/2] UefiCpuPkg/MpInitLib: Copy SEV-ES save area pointer during APIC ID sorting Lendacky, Thomas via groups.io
2023-11-28 10:33   ` Ni, Ray
     [not found] ` <17952A20A9E21541.12603@groups.io>
2023-11-06 23:15   ` Lendacky, Thomas via groups.io [this message]
2023-11-07  1:19     ` [edk2-devel] [PATCH 1/2] UefiCpuPkg/MpInitLib: Use AsmCpuidEx() for CPUID_EXTENDED_TOPOLOGY leaf Michael D Kinney
2023-11-28 14:35     ` Lendacky, Thomas via groups.io
     [not found]     ` <179BD02AA4207037.22216@groups.io>
2024-01-17 21:26       ` Lendacky, Thomas via groups.io
2024-01-18 23:10         ` Michael D Kinney
2024-01-19 10:00           ` Ni, Ray
2024-01-19 23:16             ` Michael D Kinney
2024-01-19 23:48               ` Ni, Ray
2024-01-20  1:49                 ` Michael D Kinney
2024-01-20  6:48                   ` Ni, Ray
2024-01-20 16:03                     ` Lendacky, Thomas via groups.io
2024-01-21  3:00                       ` Ni, Ray
2023-11-07  9:55 ` [edk2-devel] [PATCH 0/2] SEV-SNP guest support fixes Gerd Hoffmann
2023-11-17 21:43   ` Lendacky, Thomas via groups.io
2023-11-27 19:00     ` Lendacky, Thomas via groups.io

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