From 011751a15fd63ed7775bf94737a17dbed02a0a7b Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Thu, 16 Dec 2021 10:19:37 +0800 Subject: [PATCH] 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 22ab2e6b66fd("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 6d53f7590773("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 c56815a0d51b("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: 22ab2e6b66fd("KVM: x86: do not reset mmu if CR0.CD and CR0.NW are changed") Fixes: 6d53f7590773("KVM: x86: Invalidate all PGDs for the current PCID on MOV CR3 w/ flush") Fixes: c56815a0d51b("KVM: X86: Don't reset mmu context when toggling X86_CR4_PGE") Suggested-by: Sean Christopherson Signed-off-by: Lai Jiangshan Message-Id: <20211216021938.11752-3-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini --- 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 074a0578979f1..9ddad9493cb88 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); -- 2.39.5