On Fri, Aug 26, 2022, Jim Mattson wrote:
> Previously, KVM reported support for CPUID.(EAX=7,ECX=1) only if the
> maximum leaf 7 index on the host was exactly 1. A recent microcode
> patch for Ice Lake raised the maximum leaf 7 index from 0 to 2,
> skipping right over 1. Though that patch left CPUID.(EAX=7,ECX=1)
> filled with zeros on Ice Lake, it nonetheless exposed this bug.
>
> Report CPUID.(EAX=7,ECX=1) support if the maximum leaf 7 index on the
> host is at least 1.
>
> Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
> Fixes: bcf600ca8d21 ("KVM: x86: Remove the unnecessary loop on CPUID 0x7 sub-leafs")
> Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
> ---
> arch/x86/kvm/cpuid.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 07be45c5bb93..64cdabb3cb2c 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -886,7 +886,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
> cpuid_entry_override(entry, CPUID_7_EDX);
>
> /* KVM only supports 0x7.0 and 0x7.1, capped above via min(). */
> - if (entry->eax == 1) {
> + if (entry->eax >= 1) {
But as the comment says, above this is:
entry->eax = min(entry->eax, 1u);
...
/* KVM only supports 0x7.0 and 0x7.1, capped above via min(). */
if (entry->eax == 1) {
What am I missing?
