Re: [PATCH v2 3/4] KVM: SEV: Drop page refcount early in VMSA reload

[Michael Roth]

On Tue, Aug 18, 2026 at 09:15:54AM +0000, Ackerley Tng wrote:
> When reloading the guest VMSA for an SEV-SNP vCPU, KVM retrieves the PFN
> from guest_memfd.
> 
> Drop the page reference immediately after retrieving the PFN instead of
> holding it across MMU lock acquisition in preparation for a follow-up patch
> to stop returning page pointers from guest_memfd PFN lookups.
> 
> This is safe because the page's validity and presence are governed by KVM's
> MMU invalidation protocol rather than the page reference.
> 
> No functional change intended.
> 
> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>

Reviewed-by: Michael Roth <michael.roth@xxxxxxx>

> ---
>  arch/x86/kvm/svm/sev.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index b34b11d7f8fad..d3d620bc04dce 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -4062,6 +4062,7 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
>  	 */
>  	if (kvm_gmem_get_pfn(vcpu->kvm, slot, gfn, &pfn, &page, NULL))
>  		return;
> +	kvm_release_page_clean(page);
>  
>  	read_lock(&kvm->mmu_lock);
>  	/*
> @@ -4076,8 +4077,6 @@ static void __sev_snp_reload_vmsa(struct kvm_vcpu *vcpu, gpa_t gpa)
>  	else
>  		svm->vmcb->control.vmsa_pa = pfn_to_hpa(pfn);
>  	read_unlock(&kvm->mmu_lock);
> -
> -	kvm_release_page_clean(page);
>  }
>  
>  /*
> 
> -- 
> 2.55.0.699.gb54405d56f-goog
>