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KVM: x86: skip host CPUID call for hypervisor leaves

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Hypervisor leaves are always synthesized by __do_cpuid_func; just return
zeroes and do not ask the host.  Even on nested virtualization, a value
from another hypervisor would be bogus, because all hypercalls and MSRs
are processed by KVM.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2021-10-28 13:15:55 -04:00
parent 9d68c6f60e
commit 2746a6b72a
1 changed files with 9 additions and 1 deletions
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10
arch/x86/kvm/cpuid.c
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@ -712,9 +712,17 @@ static struct kvm_cpuid_entry2 *do_host_cpuid(struct kvm_cpuid_array *array,
entry = &array->entries[array->nent++];
memset(entry, 0, sizeof(*entry));
entry->function = function;
entry->index = index;
entry->flags = 0;
switch (function & 0xC0000000) {
case 0x40000000:
/* Hypervisor leaves are always synthesized by __do_cpuid_func. */
return entry;
default:
break;
}
cpuid_count(entry->function, entry->index,
&entry->eax, &entry->ebx, &entry->ecx, &entry->edx);