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From:   "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
To:     Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>
Cc:     Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v3 07/12] KVM: x86: Trace re-injected exceptions
Date:   Mon,  2 May 2022 00:07:31 +0200
Message-Id: <25470690a38b4d2b32b6204875dd35676c65c9f2.1651440202.git.maciej.szmigiero@oracle.com>
In-Reply-To: <cover.1651440202.git.maciej.szmigiero@oracle.com>
References: <cover.1651440202.git.maciej.szmigiero@oracle.com>
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From: Sean Christopherson <seanjc@google.com>

Trace exceptions that are re-injected, not just those that KVM is
injecting for the first time.  Debugging re-injection bugs is painful
enough as is, not having visibility into what KVM is doing only makes
things worse.

Delay propagating pending=>injected in the non-reinjection path so that
the tracing can properly identify reinjected exceptions.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
 arch/x86/kvm/trace.h | 12 ++++++++----
 arch/x86/kvm/x86.c   | 16 +++++++++-------
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index de4762517569..d07428e660e3 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -358,25 +358,29 @@ TRACE_EVENT(kvm_inj_virq,
  * Tracepoint for kvm interrupt injection:
  */
 TRACE_EVENT(kvm_inj_exception,
-	TP_PROTO(unsigned exception, bool has_error, unsigned error_code),
-	TP_ARGS(exception, has_error, error_code),
+	TP_PROTO(unsigned exception, bool has_error, unsigned error_code,
+		 bool reinjected),
+	TP_ARGS(exception, has_error, error_code, reinjected),
 
 	TP_STRUCT__entry(
 		__field(	u8,	exception	)
 		__field(	u8,	has_error	)
 		__field(	u32,	error_code	)
+		__field(	bool,	reinjected	)
 	),
 
 	TP_fast_assign(
 		__entry->exception	= exception;
 		__entry->has_error	= has_error;
 		__entry->error_code	= error_code;
+		__entry->reinjected	= reinjected;
 	),
 
-	TP_printk("%s (0x%x)",
+	TP_printk("%s (0x%x)%s",
 		  __print_symbolic(__entry->exception, kvm_trace_sym_exc),
 		  /* FIXME: don't print error_code if not present */
-		  __entry->has_error ? __entry->error_code : 0)
+		  __entry->has_error ? __entry->error_code : 0,
+		  __entry->reinjected ? " [reinjected]" : "")
 );
 
 /*
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1abce22b14d7..a41d616ad943 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9393,6 +9393,11 @@ int kvm_check_nested_events(struct kvm_vcpu *vcpu)
 
 static void kvm_inject_exception(struct kvm_vcpu *vcpu)
 {
+	trace_kvm_inj_exception(vcpu->arch.exception.nr,
+				vcpu->arch.exception.has_error_code,
+				vcpu->arch.exception.error_code,
+				vcpu->arch.exception.injected);
+
 	if (vcpu->arch.exception.error_code && !is_protmode(vcpu))
 		vcpu->arch.exception.error_code = false;
 	static_call(kvm_x86_queue_exception)(vcpu);
@@ -9450,13 +9455,6 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
 
 	/* try to inject new event if pending */
 	if (vcpu->arch.exception.pending) {
-		trace_kvm_inj_exception(vcpu->arch.exception.nr,
-					vcpu->arch.exception.has_error_code,
-					vcpu->arch.exception.error_code);
-
-		vcpu->arch.exception.pending = false;
-		vcpu->arch.exception.injected = true;
-
 		if (exception_type(vcpu->arch.exception.nr) == EXCPT_FAULT)
 			__kvm_set_rflags(vcpu, kvm_get_rflags(vcpu) |
 					     X86_EFLAGS_RF);
@@ -9470,6 +9468,10 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
 		}
 
 		kvm_inject_exception(vcpu);
+
+		vcpu->arch.exception.pending = false;
+		vcpu->arch.exception.injected = true;
+
 		can_inject = false;
 	}