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Subject[PATCH 25/28] KVM: nSVM: leave guest mode when clearing EFER.SVME
Date
According to the AMD manual, the effect of turning off EFER.SVME while a
guest is running is undefined. We make it leave guest mode immediately,
similar to the effect of clearing the VMX bit in MSR_IA32_FEAT_CTL.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/svm/nested.c | 16 ++++++++++++++++
arch/x86/kvm/svm/svm.c | 10 ++++++++--
arch/x86/kvm/svm/svm.h | 1 +
3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index a504963ef532..e63e62d12acd 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -618,6 +618,22 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
return 0;
}

+/*
+ * Forcibly leave nested mode in order to be able to reset the VCPU later on.
+ */
+void svm_leave_nested(struct vcpu_svm *svm)
+{
+ if (is_guest_mode(&svm->vcpu)) {
+ struct vmcb *hsave = svm->nested.hsave;
+ struct vmcb *vmcb = svm->vmcb;
+
+ svm->nested.nested_run_pending = 0;
+ leave_guest_mode(&svm->vcpu);
+ copy_vmcb_control_area(&vmcb->control, &hsave->control);
+ nested_svm_uninit_mmu_context(&svm->vcpu);
+ }
+}
+
static int nested_svm_exit_handled_msr(struct vcpu_svm *svm)
{
u32 offset, msr, value;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index f0da6f0ebf1b..c1e746ccd7da 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -265,6 +265,7 @@ static int get_npt_level(struct kvm_vcpu *vcpu)

void svm_set_efer(struct kvm_vcpu *vcpu, u64 efer)
{
+ struct vcpu_svm *svm = to_svm(vcpu);
vcpu->arch.efer = efer;

if (!npt_enabled) {
@@ -275,8 +276,13 @@ void svm_set_efer(struct kvm_vcpu *vcpu, u64 efer)
efer &= ~EFER_LME;
}

- to_svm(vcpu)->vmcb->save.efer = efer | EFER_SVME;
- mark_dirty(to_svm(vcpu)->vmcb, VMCB_CR);
+ if (!(efer & EFER_SVME)) {
+ svm_leave_nested(svm);
+ svm_set_gif(svm, true);
+ }
+
+ svm->vmcb->save.efer = efer | EFER_SVME;
+ mark_dirty(svm->vmcb, VMCB_CR);
}

static int is_external_interrupt(u32 info)
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index be8e830f83fa..6ac4c00a5d82 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -389,6 +389,7 @@ static inline bool nested_exit_on_nmi(struct vcpu_svm *svm)

void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
struct vmcb *nested_vmcb);
+void svm_leave_nested(struct vcpu_svm *svm);
int nested_svm_vmrun(struct vcpu_svm *svm);
void nested_svm_vmloadsave(struct vmcb *from_vmcb, struct vmcb *to_vmcb);
int nested_svm_vmexit(struct vcpu_svm *svm);
--
2.26.2

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