Re: [PATCH 2/3] KVM: x86: Report CPUID.7.1 support on CPUs with CPUID.7 indices > 1

[Sean Christopherson <seanjc@google.com>]

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@google.com>
> Fixes: bcf600ca8d21 ("KVM: x86: Remove the unnecessary loop on CPUID 0x7 sub-leafs")
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---
>  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?