From: Lai Jiangshan laijs@linux.alibaba.com
[ Upstream commit 6b123c3a89a90ac6418e4d64b1e23f09d458a77d ]
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 d81135a57aa6("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 21823fbda552("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 a91a7c709600("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: d81135a57aa6("KVM: x86: do not reset mmu if CR0.CD and CR0.NW are changed") Fixes: 21823fbda552("KVM: x86: Invalidate all PGDs for the current PCID on MOV CR3 w/ flush") Fixes: a91a7c709600("KVM: X86: Don't reset mmu context when toggling X86_CR4_PGE") Suggested-by: Sean Christopherson seanjc@google.com Signed-off-by: Lai Jiangshan laijs@linux.alibaba.com Message-Id: 20211216021938.11752-3-jiangshanlai@gmail.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Mathias Krause minipli@grsecurity.net --- arch/x86/kvm/x86.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 038ac5bbdd19..065e1a5b3b94 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -792,6 +792,13 @@ int load_pdptrs(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, unsigned long cr3) } ret = 1;
+ /* + * 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);