[PATCH v3 4/8] KVM: nSVM: refactor the CR3 reload on migration
From: Maxim Levitsky <hidden>
Date: 2021-06-07 09:02:45
Also in:
kvm, lkml
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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 <redacted> --- 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 8f5dbc80f57f..e3e5775b8f1c 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;
@@ -803,7 +803,7 @@ 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;
@@ -1299,6 +1299,19 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu, !nested_vmcb_valid_sregs(vcpu, save)) 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
@@ -1356,9 +1369,14 @@ 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;
--
2.26.3