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    Subject[PATCH] KVM: x86/cpuid: Clear XFD for component i if the base feature is missing
    Date
    From: Like Xu <likexu@tencent.com>

    According to Intel extended feature disable (XFD) spec, the sub-function i
    (i > 1) of CPUID function 0DH enumerates "details for state component i.
    ECX[2] enumerates support for XFD support for this state component."

    If KVM does not report F(XFD) feature (e.g. due to CONFIG_X86_64),
    then the corresponding XFD support for any state component i
    should also be removed. Translate this dependency into KVM terms.

    Fixes: 690a757d610e ("kvm: x86: Add CPUID support for Intel AMX")
    Signed-off-by: Like Xu <likexu@tencent.com>
    ---
    arch/x86/kvm/cpuid.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
    index c55e57b30e81..e96efef4f048 100644
    --- a/arch/x86/kvm/cpuid.c
    +++ b/arch/x86/kvm/cpuid.c
    @@ -886,6 +886,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
    --array->nent;
    continue;
    }
    +
    + if (!kvm_cpu_cap_has(X86_FEATURE_XFD))
    + entry->ecx &= ~BIT_ULL(2);
    entry->edx = 0;
    }
    break;
    --
    2.33.1
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