Commit 6b123c3a authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Reconstruct shadow page root if the guest PDPTEs is changed 



For shadow paging, the page table needs to be reconstructed before the
coming VMENTER if the guest PDPTEs is changed.

But not all paths that call load_pdptrs() will cause the page tables to be
reconstructed. Normally, kvm_mmu_reset_context() and kvm_mmu_free_roots()
are used to launch later reconstruction.

The commit d81135a5("KVM: x86: do not reset mmu if CR0.CD and
CR0.NW are changed") skips kvm_mmu_reset_context() after load_pdptrs()
when changing CR0.CD and CR0.NW.

The commit 21823fbd("KVM: x86: Invalidate all PGDs for the current
PCID on MOV CR3 w/ flush") skips kvm_mmu_free_roots() after
load_pdptrs() when rewriting the CR3 with the same value.

The commit a91a7c70("KVM: X86: Don't reset mmu context when
toggling X86_CR4_PGE") skips kvm_mmu_reset_context() after
load_pdptrs() when changing CR4.PGE.

Guests like linux would keep the PDPTEs unchanged for every instance of
pagetable, so this missing reconstruction has no problem for linux
guests.

Fixes: d81135a5("KVM: x86: do not reset mmu if CR0.CD and CR0.NW are changed")
Fixes: 21823fbd("KVM: x86: Invalidate all PGDs for the current PCID on MOV CR3 w/ flush")
Fixes: a91a7c70("KVM: X86: Don't reset mmu context when toggling X86_CR4_PGE")
Suggested-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarLai Jiangshan <laijs@linux.alibaba.com>
Message-Id: <20211216021938.11752-3-jiangshanlai@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a9f2705e

arch/x86/kvm/x86.c

+7 −0
Original line number Diff line number Diff line
@@ -841,6 +841,13 @@ int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3) 
		}

	}



	/*

	 * Marking VCPU_EXREG_PDPTR dirty doesn't work for !tdp_enabled.

	 * Shadow page roots need to be reconstructed instead.

	 */

	if (!tdp_enabled && memcmp(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs)))

		kvm_mmu_free_roots(vcpu, mmu, KVM_MMU_ROOT_CURRENT);



	memcpy(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs));

	kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);

	kvm_make_request(KVM_REQ_LOAD_MMU_PGD, vcpu);