Re: [PATCH v2 15/49] KVM: x86: Zero out PV features cache when the CPUID leaf is not present

[Maxim Levitsky]

On Fri, 2024-05-17 at 10:38 -0700, Sean Christopherson wrote:
> Clear KVM's PV feature cache prior when processing a new guest CPUID so
> that KVM doesn't keep a stale cache entry if userspace does KVM_SET_CPUID2
> multiple times, once with a PV features entry, and a second time without.
> 
> Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
> Cc: Oliver Upton <oliver.upton@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>  arch/x86/kvm/cpuid.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index f756a91a3f2f..be1c8f43e090 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -246,6 +246,8 @@ void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_cpuid_entry2 *best = kvm_find_kvm_cpuid_features(vcpu);
>  
> +	vcpu->arch.pv_cpuid.features = 0;
> +
>  	/*
>  	 * save the feature bitmap to avoid cpuid lookup for every PV
>  	 * operation

Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>

Best regards,
	Maxim Levitsky