tree bd795eca0fc821ca5f21b509d4a52cf2a23052a9
parent 88dd4ca06c8392155289e5462cd26af3762a1b04
author Zhao Liu <zhao1.liu@intel.com> 1713973755 +0800
committer Paolo Bonzini <pbonzini@redhat.com> 1716399809 +0200

i386/cpu: Use APIC ID info get NumSharingCache for CPUID[0x8000001D].EAX[bits 25:14]

The commit 8f4202fb1080 ("i386: Populate AMD Processor Cache Information
for cpuid 0x8000001D") adds the cache topology for AMD CPU by encoding
the number of sharing threads directly.

From AMD's APM, NumSharingCache (CPUID[0x8000001D].EAX[bits 25:14])
means [1]:

The number of logical processors sharing this cache is the value of
this field incremented by 1. To determine which logical processors are
sharing a cache, determine a Share Id for each processor as follows:

ShareId = LocalApicId >> log2(NumSharingCache+1)

Logical processors with the same ShareId then share a cache. If
NumSharingCache+1 is not a power of two, round it up to the next power
of two.

From the description above, the calculation of this field should be same
as CPUID[4].EAX[bits 25:14] for Intel CPUs. So also use the offsets of
APIC ID to calculate this field.

[1]: APM, vol.3, appendix.E.4.15 Function 8000_001Dh--Cache Topology
     Information

Tested-by: Yongwei Ma <yongwei.ma@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-ID: <20240424154929.1487382-8-zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>