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KVM: SEV: Drop page refcount early in VMSA reload

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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.

Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Link: https://patch.msgid.link/20260826-gmem-no-return-page-v4-4-3bb9c1ddb4e3@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Ackerley Tng 2026-08-26 09:01:49 +00:00 committed by Sean Christopherson
parent acafcf32c8
commit 3c427e5c03
1 changed files with 1 additions and 2 deletions
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3
arch/x86/kvm/svm/sev.c
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@ -4078,6 +4078,7 @@ 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);
/*
@ -4092,8 +4093,6 @@ 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);
}
/*