Messages in this thread | | | Subject | Re: [PATCH 06/30] KVM: SVM: always update CR3 in VMCB | From | Krish Sadhukhan <> | Date | Fri, 29 May 2020 10:41:58 -0700 |
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On 5/29/20 8:39 AM, Paolo Bonzini wrote: > svm_load_mmu_pgd is delaying the write of GUEST_CR3 to prepare_vmcs02
Did you mean to say enter_svm_guest_mode here ? > as > an optimization, but this is only correct before the nested vmentry. > If userspace is modifying CR3 with KVM_SET_SREGS after the VM has > already been put in guest mode, the value of CR3 will not be updated. > Remove the optimization, which almost never triggers anyway. > This was was added in commit 689f3bf21628 ("KVM: x86: unify callbacks > to load paging root", 2020-03-16) just to keep the two vendor-specific > modules closer, but we'll fix VMX too. > > Fixes: 689f3bf21628 ("KVM: x86: unify callbacks to load paging root") > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > arch/x86/kvm/svm/nested.c | 6 +----- > arch/x86/kvm/svm/svm.c | 16 +++++----------- > 2 files changed, 6 insertions(+), 16 deletions(-) > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > index dcac4c3510ab..8756c9f463fd 100644 > --- a/arch/x86/kvm/svm/nested.c > +++ b/arch/x86/kvm/svm/nested.c > @@ -256,11 +256,7 @@ void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa, > svm_set_efer(&svm->vcpu, nested_vmcb->save.efer); > svm_set_cr0(&svm->vcpu, nested_vmcb->save.cr0); > svm_set_cr4(&svm->vcpu, nested_vmcb->save.cr4); > - if (npt_enabled) { > - svm->vmcb->save.cr3 = nested_vmcb->save.cr3; > - svm->vcpu.arch.cr3 = nested_vmcb->save.cr3; > - } else > - (void)kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3); > + (void)kvm_set_cr3(&svm->vcpu, nested_vmcb->save.cr3); > > /* Guest paging mode is active - reset mmu */ > kvm_mmu_reset_context(&svm->vcpu); > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 545f63ebc720..feb96a410f2d 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -3447,7 +3447,6 @@ static fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu) > static void svm_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long root) > { > struct vcpu_svm *svm = to_svm(vcpu); > - bool update_guest_cr3 = true; > unsigned long cr3; > > cr3 = __sme_set(root); > @@ -3456,18 +3455,13 @@ static void svm_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long root) > mark_dirty(svm->vmcb, VMCB_NPT); > > /* Loading L2's CR3 is handled by enter_svm_guest_mode. */ > - if (is_guest_mode(vcpu)) > - update_guest_cr3 = false; > - else if (test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail)) > - cr3 = vcpu->arch.cr3; > - else /* CR3 is already up-to-date. */ > - update_guest_cr3 = false; > + if (!test_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail)) > + return; > + cr3 = vcpu->arch.cr3; > } > > - if (update_guest_cr3) { > - svm->vmcb->save.cr3 = cr3; > - mark_dirty(svm->vmcb, VMCB_CR); > - } > + svm->vmcb->save.cr3 = cr3; > + mark_dirty(svm->vmcb, VMCB_CR); > } > > static int is_disabled(void)
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