[PATCH 14/21] KVM: x86: Formalize blocking of nested pending exceptions

Sean Christopherson
2022-03-11T03:29:28Z

Capture nested_run_pending as block_pending_exceptions so that the logic
of why exceptions are blocked only needs to be documented once instead of
at every place that employs the logic.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/nested.c | 20 ++++++++++----------
arch/x86/kvm/vmx/nested.c | 23 ++++++++++++-----------
2 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index bef5a93166a8..60df9d4d19b5 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1201,10 +1201,16 @@ static inline bool nested_exit_on_init(struct vcpu_svm *svm)

static int svm_check_nested_events(struct kvm_vcpu *vcpu)
{
- struct vcpu_svm *svm = to_svm(vcpu);
- bool block_nested_events =
- kvm_event_needs_reinjection(vcpu) || svm->nested.nested_run_pending;
struct kvm_lapic *apic = vcpu->arch.apic;
+ struct vcpu_svm *svm = to_svm(vcpu);
+ /*
+ * Only a pending nested run blocks a pending exception. If there is a
+ * previously injected event, the pending exception occurred while said
+ * event was being delivered and thus needs to be handled.
+ */
+ bool block_nested_exceptions = svm->nested.nested_run_pending;
+ bool block_nested_events = block_nested_exceptions ||
+ kvm_event_needs_reinjection(vcpu);

if (lapic_in_kernel(vcpu) &&
test_bit(KVM_APIC_INIT, &apic->pending_events)) {
@@ -1217,13 +1223,7 @@ static int svm_check_nested_events(struct kvm_vcpu *vcpu)
}

if (vcpu->arch.exception.pending) {
- /*
- * Only a pending nested run can block a pending exception.
- * Otherwise an injected NMI/interrupt should either be
- * lost or delivered to the nested hypervisor in the EXITINTINFO
- * vmcb field, while delivering the pending exception.
- */
- if (svm->nested.nested_run_pending)
+ if (block_nested_exceptions)
return -EBUSY;
if (!nested_exit_on_exception(svm))
return 0;
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index c88031d44148..01cf579c0260 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3878,11 +3878,17 @@ static bool nested_vmx_preemption_timer_pending(struct kvm_vcpu *vcpu)

static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
{
- struct vcpu_vmx *vmx = to_vmx(vcpu);
- unsigned long exit_qual;
- bool block_nested_events =
- vmx->nested.nested_run_pending || kvm_event_needs_reinjection(vcpu);
struct kvm_lapic *apic = vcpu->arch.apic;
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ unsigned long exit_qual;
+ /*
+ * Only a pending nested run blocks a pending exception. If there is a
+ * previously injected event, the pending exception occurred while said
+ * event was being delivered and thus needs to be handled.
+ */
+ bool block_nested_exceptions = vmx->nested.nested_run_pending;
+ bool block_nested_events = block_nested_exceptions ||
+ kvm_event_needs_reinjection(vcpu);

if (lapic_in_kernel(vcpu) &&
test_bit(KVM_APIC_INIT, &apic->pending_events)) {
@@ -3916,15 +3922,10 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
* Process exceptions that are higher priority than Monitor Trap Flag:
* fault-like exceptions, TSS T flag #DB (not emulated by KVM, but
* could theoretically come in from userspace), and ICEBP (INT1).
- *
- * Note that only a pending nested run can block a pending exception.
- * Otherwise an injected NMI/interrupt should either be
- * lost or delivered to the nested hypervisor in the IDT_VECTORING_INFO,
- * while delivering the pending exception.
*/
if (vcpu->arch.exception.pending &&
!(vmx_get_pending_dbg_trap(vcpu) & ~DR6_BT)) {
- if (vmx->nested.nested_run_pending)
+ if (block_nested_exceptions)
return -EBUSY;
if (!nested_vmx_check_exception(vcpu, &exit_qual))
goto no_vmexit;
@@ -3941,7 +3942,7 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
}

if (vcpu->arch.exception.pending) {
- if (vmx->nested.nested_run_pending)
+ if (block_nested_exceptions)
return -EBUSY;
if (!nested_vmx_check_exception(vcpu, &exit_qual))
goto no_vmexit;
--
2.35.1.723.g4982287a31-goog