Messages in this thread Patch in this message | | | From | Lai Jiangshan <> | Subject | [PATCH V2 2/3] KVM: x86/mmu: Ensure pae_root to be reconstructed for shadow paging if the guest PDPTEs is changed | Date | Thu, 16 Dec 2021 10:19:37 +0800 |
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From: Lai Jiangshan <laijs@linux.alibaba.com>
For shadow paging, the pae_root 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 pae_root 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> --- 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 af22ad79e081..71c389a47801 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -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); -- 2.19.1.6.gb485710b
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