[edk2-devel] [PATCH v2 1/1] UefiCpuPkg/BaseXApicX2ApicLib: fix CPUID_V2_EXTENDED_TOPOLOGY detection
Laszlo Ersek
lersek at redhat.com
Wed Oct 25 10:09:51 UTC 2023
On 10/17/23 13:28, Gerd Hoffmann wrote:
> Checking the max cpuid leaf is not enough to figure whenever
> CPUID_V2_EXTENDED_TOPOLOGY is supported. Intel SDM says:
>
> Software must detect the presence of CPUID leaf 1FH by verifying
> (a) the highest leaf index supported by CPUID is >= 1FH, and
> (b) CPUID.1FH:EBX[15:0] reports a non-zero value.
>
> The same is true for CPUID leaf 0BH.
>
> This patch adds the EBX check to GetProcessorLocation2ByApicId(). The
> patch also fixes the existing check in GetProcessorLocationByApicId() to
> be in line with the spec by looking at bits 15:0. The comments are
> updated with a quote from the Intel SDM.
>
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2241388
> Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
> ---
> .../BaseXApicX2ApicLib/BaseXApicX2ApicLib.c | 21 ++++++++++++++-----
> 1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
> index aa4eb11181f6..c0a847583330 100644
> --- a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
> +++ b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
> @@ -1294,11 +1294,12 @@ GetProcessorLocationByApicId (
> NULL
> );
> //
> - // If CPUID.(EAX=0BH, ECX=0H):EBX returns zero and maximum input value for
> - // basic CPUID information is greater than 0BH, then CPUID.0BH leaf is not
> - // supported on that processor.
> + // Quoting Intel SDM:
> + // Software must detect the presence of CPUID leaf 0BH by
> + // verifying (a) the highest leaf index supported by CPUID is >=
> + // 0BH, and (b) CPUID.0BH:EBX[15:0] reports a non-zero value.
> //
> - if (ExtendedTopologyEbx.Uint32 != 0) {
> + if (ExtendedTopologyEbx.Bits.LogicalProcessors != 0) {
> TopologyLeafSupported = TRUE;
>
> //
> @@ -1424,6 +1425,7 @@ GetProcessorLocation2ByApicId (
> )
> {
> CPUID_EXTENDED_TOPOLOGY_EAX ExtendedTopologyEax;
> + CPUID_EXTENDED_TOPOLOGY_EBX ExtendedTopologyEbx;
> CPUID_EXTENDED_TOPOLOGY_ECX ExtendedTopologyEcx;
> UINT32 MaxStandardCpuIdIndex;
> UINT32 Index;
> @@ -1436,10 +1438,19 @@ GetProcessorLocation2ByApicId (
> }
>
> //
> - // Get max index of CPUID
> + // Quoting Intel SDM:
> + // Software must detect the presence of CPUID leaf 1FH by verifying
> + // (a) the highest leaf index supported by CPUID is >= 1FH, and (b)
> + // CPUID.1FH:EBX[15:0] reports a non-zero value.
> //
> AsmCpuid (CPUID_SIGNATURE, &MaxStandardCpuIdIndex, NULL, NULL, NULL);
> if (MaxStandardCpuIdIndex < CPUID_V2_EXTENDED_TOPOLOGY) {
> + ExtendedTopologyEbx.Bits.LogicalProcessors = 0;
> + } else {
> + AsmCpuidEx (CPUID_V2_EXTENDED_TOPOLOGY, 0, NULL, &ExtendedTopologyEbx.Uint32, NULL, NULL);
> + }
> +
> + if (ExtendedTopologyEbx.Bits.LogicalProcessors == 0) {
> if (Die != NULL) {
> *Die = 0;
> }
Commit 170d4ce8e90abb1eff03852940a69c9d17f8afe5 (via #4954).
Laszlo
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