Re: [PATCH v7 5/8] KVM: x86/mmu: Don't pass FOLL_GET to __kvm_follow_pfn
From: Yan Zhao <hidden>
Date: 2023-07-19 06:36:06
Also in:
kvm, kvmarm, linux-arm-kernel, lkml
On Tue, Jul 04, 2023 at 04:50:50PM +0900, David Stevens wrote:
quoted hunk ↗ jump to hunk
@@ -4451,7 +4461,8 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault out_unlock: write_unlock(&vcpu->kvm->mmu_lock); - kvm_release_pfn_clean(fault->pfn); + if (fault->is_refcounted_page) + kvm_set_page_accessed(pfn_to_page(fault->pfn));
For a refcounted page, as now KVM puts its ref early in kvm_faultin_pfn(), should this kvm_set_page_accessed() be placed before unlocking mmu_lock? Otherwise, if the user unmaps a region (which triggers kvm_unmap_gfn_range() with mmu_lock holding for write), and release the page, and if the two steps happen after checking page_count() in kvm_set_page_accessed() and before mark_page_accessed(), the latter function may mark accessed to a page that is released or does not belong to current process. Is it true?
quoted hunk ↗ jump to hunk
return r; }@@ -4529,7 +4540,8 @@ static int kvm_tdp_mmu_page_fault(struct kvm_vcpu *vcpu, out_unlock: read_unlock(&vcpu->kvm->mmu_lock); - kvm_release_pfn_clean(fault->pfn); + if (fault->is_refcounted_page) + kvm_set_page_accessed(pfn_to_page(fault->pfn)); return r; }
Ditto.