linux-kernel - [PATCH 1/3] KVM: x86: make vendor code check for all nested events

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Date:   Wed, 27 Apr 2022 13:37:56 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     mlevitsk@...hat.com, seanjc@...gle.com, stable@...r.kernel.org
Subject: [PATCH 1/3] KVM: x86: make vendor code check for all nested events

Right now, the VMX preemption timer is special cased via the
hv_timer_pending, but the purpose of the callback can be easily
extended to observing any event that can occur only in non-root
mode.  Interrupts, NMIs etc. are already handled properly by
the *_interrupt_allowed callbacks, so what is missing is only
MTF.  Check it in the newly-renamed callback, so that
kvm_vcpu_running's call to kvm_check_nested_events
becomes redundant.

Cc: stable@...r.kernel.org
Reported-by: Maxim Levitsky <mlevitsk@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/include/asm/kvm_host.h | 2 +-
 arch/x86/kvm/vmx/nested.c       | 7 ++++++-
 arch/x86/kvm/x86.c              | 8 ++++----
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4ff36610af6a..e2e4f60159e9 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1504,7 +1504,7 @@ struct kvm_x86_ops {
 struct kvm_x86_nested_ops {
 	void (*leave_nested)(struct kvm_vcpu *vcpu);
 	int (*check_events)(struct kvm_vcpu *vcpu);
-	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 856c87563883..54672025c3a1 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3857,6 +3857,11 @@ 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)
+{
+	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);
@@ -6809,7 +6814,7 @@ __init int nested_vmx_hardware_setup(int (*exit_handlers[])(struct kvm_vcpu *))
 struct kvm_x86_nested_ops vmx_nested_ops = {
 	.leave_nested = vmx_leave_nested,
 	.check_events = vmx_check_nested_events,
-	.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 a6ab19afc638..0e73607b02bd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9471,8 +9471,8 @@ 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);
@@ -12183,8 +12183,8 @@ 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;
 
 	return false;
-- 
2.31.1