[PATCH v2 6/9] KVM: x86: make vendor code check for all nested events

Paolo Bonzini
2022-08-11T21:06:40Z

Interrupts, NMIs etc. sent while in guest mode are already handled
properly by the *_interrupt_allowed callbacks, but other events can
cause a vCPU to be runnable that are specific to guest mode.

In the case of VMX there are two, the preemption timer and the
monitor trap. The VMX preemption timer is already special cased via
the hv_timer_pending callback, but the purpose of the callback can be
easily extended to MTF or in fact any other event that can occur only
in guest mode.

Rename the callback and add an MTF check; kvm_arch_vcpu_runnable()
now will return true if an MTF is pending, without relying on
kvm_vcpu_running()'s call to kvm_check_nested_events(). Until that call
is removed, however, the patch introduces no functional change.

Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/vmx/nested.c | 9 ++++++++-
arch/x86/kvm/x86.c | 8 ++++----
3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5ffa578cafe1..293ff678fff5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1636,7 +1636,7 @@ struct kvm_x86_nested_ops {
int (*check_events)(struct kvm_vcpu *vcpu);
bool (*handle_page_fault_workaround)(struct kvm_vcpu *vcpu,
struct x86_exception *fault);
- bool (*hv_timer_pending)(struct kvm_vcpu *vcpu);
+ bool (*has_events)(struct kvm_vcpu *vcpu);
void (*triple_fault)(struct kvm_vcpu *vcpu);
int (*get_state)(struct kvm_vcpu *vcpu,
struct kvm_nested_state __user *user_kvm_nested_state,
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index ddd4367d4826..9631cdcdd058 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3876,6 +3876,13 @@ static bool nested_vmx_preemption_timer_pending(struct kvm_vcpu *vcpu)
to_vmx(vcpu)->nested.preemption_timer_expired;
}

+static bool vmx_has_nested_events(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+ return nested_vmx_preemption_timer_pending(vcpu) || vmx->nested.mtf_pending;
+}
+
static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -6816,7 +6823,7 @@ struct kvm_x86_nested_ops vmx_nested_ops = {
.leave_nested = vmx_leave_nested,
.check_events = vmx_check_nested_events,
.handle_page_fault_workaround = nested_vmx_handle_page_fault_workaround,
- .hv_timer_pending = nested_vmx_preemption_timer_pending,
+ .has_events = vmx_has_nested_events,
.triple_fault = nested_vmx_triple_fault,
.get_state = vmx_get_nested_state,
.set_state = vmx_set_nested_state,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7f084613fac8..0f9f24793b8a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9789,8 +9789,8 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
}

if (is_guest_mode(vcpu) &&
- kvm_x86_ops.nested_ops->hv_timer_pending &&
- kvm_x86_ops.nested_ops->hv_timer_pending(vcpu))
+ kvm_x86_ops.nested_ops->has_events &&
+ kvm_x86_ops.nested_ops->has_events(vcpu))
*req_immediate_exit = true;

WARN_ON(vcpu->arch.exception.pending);
@@ -12562,8 +12562,8 @@ static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
return true;

if (is_guest_mode(vcpu) &&
- kvm_x86_ops.nested_ops->hv_timer_pending &&
- kvm_x86_ops.nested_ops->hv_timer_pending(vcpu))
+ kvm_x86_ops.nested_ops->has_events &&
+ kvm_x86_ops.nested_ops->has_events(vcpu))
return true;

if (kvm_xen_has_pending_events(vcpu))
--
2.31.1