From 2746a6b72ab9a92bd188c4ac3e4122ee1c18f754 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 28 Oct 2021 13:15:55 -0400 Subject: [PATCH] KVM: x86: skip host CPUID call for hypervisor leaves 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 Signed-off-by: Paolo Bonzini --- arch/x86/kvm/cpuid.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 494d4d3..ff756cd 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -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); -- 2.7.4