From b222b0b88162bdef4eceb12a79d5edbbdb23dbfd Mon Sep 17 00:00:00 2001 From: Maxim Levitsky Date: Mon, 7 Jun 2021 12:01:59 +0300 Subject: [PATCH] KVM: nSVM: refactor the CR3 reload on migration Document the actual reason why we need to do it on migration and move the call to svm_set_nested_state to be closer to VMX code. To avoid loading the PDPTRs from possibly not up to date memory map, in nested_svm_load_cr3 after the move, move this code to .get_nested_state_pages. Signed-off-by: Maxim Levitsky Message-Id: <20210607090203.133058-5-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/nested.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index f0a7f84..e917eba 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -385,12 +385,12 @@ static inline bool nested_npt_enabled(struct vcpu_svm *svm) * if we are emulating VM-Entry into a guest with NPT enabled. */ static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, - bool nested_npt) + bool nested_npt, bool reload_pdptrs) { if (CC(kvm_vcpu_is_illegal_gpa(vcpu, cr3))) return -EINVAL; - if (!nested_npt && is_pae_paging(vcpu) && + if (reload_pdptrs && !nested_npt && is_pae_paging(vcpu) && CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))) return -EINVAL; @@ -574,7 +574,7 @@ int enter_svm_guest_mode(struct kvm_vcpu *vcpu, u64 vmcb12_gpa, nested_vmcb02_prepare_save(svm, vmcb12); ret = nested_svm_load_cr3(&svm->vcpu, vmcb12->save.cr3, - nested_npt_enabled(svm)); + nested_npt_enabled(svm), true); if (ret) return ret; @@ -801,7 +801,7 @@ int nested_svm_vmexit(struct vcpu_svm *svm) nested_svm_uninit_mmu_context(vcpu); - rc = nested_svm_load_cr3(vcpu, svm->vmcb->save.cr3, false); + rc = nested_svm_load_cr3(vcpu, svm->vmcb->save.cr3, false, true); if (rc) return 1; @@ -1298,6 +1298,19 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, goto out_free; /* + * While the nested guest CR3 is already checked and set by + * KVM_SET_SREGS, it was set when nested state was yet loaded, + * thus MMU might not be initialized correctly. + * Set it again to fix this. + */ + + ret = nested_svm_load_cr3(&svm->vcpu, vcpu->arch.cr3, + nested_npt_enabled(svm), false); + if (WARN_ON_ONCE(ret)) + goto out_free; + + + /* * All checks done, we can enter guest mode. Userspace provides * vmcb12.control, which will be combined with L1 and stored into * vmcb02, and the L1 save state which we store in vmcb01. @@ -1354,9 +1367,14 @@ static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu) if (WARN_ON(!is_guest_mode(vcpu))) return true; - if (nested_svm_load_cr3(&svm->vcpu, vcpu->arch.cr3, - nested_npt_enabled(svm))) - return false; + if (!nested_npt_enabled(svm) && is_pae_paging(vcpu)) + /* + * Reload the guest's PDPTRs since after a migration + * the guest CR3 might be restored prior to setting the nested + * state which can lead to a load of wrong PDPTRs. + */ + if (CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, vcpu->arch.cr3))) + return false; if (!nested_svm_vmrun_msrpm(svm)) { vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; -- 2.7.4