linux-kernel - [PATCH v2] KVM: x86: Add tracepoint for dr_write/dr

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Message-Id: <20201009032130.6774-1-lihaiwei.kernel@gmail.com>
Date:   Fri,  9 Oct 2020 11:21:30 +0800
From:   lihaiwei.kernel@...il.com
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     pbonzini@...hat.com, sean.j.christopherson@...el.com,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, Haiwei Li <lihaiwei@...cent.com>
Subject: [PATCH v2] KVM: x86: Add tracepoint for dr_write/dr_read

From: Haiwei Li <lihaiwei@...cent.com>

When vmexit occurs caused by accessing dr, there is no tracepoint to track
this action. Add tracepoint for this on x86 kvm.

Signed-off-by: Haiwei Li <lihaiwei@...cent.com>
---
v1 -> v2:
 * Improve the changelog 

 arch/x86/kvm/svm/svm.c |  2 ++
 arch/x86/kvm/trace.h   | 27 +++++++++++++++++++++++++++
 arch/x86/kvm/vmx/vmx.c | 10 ++++++++--
 arch/x86/kvm/x86.c     |  1 +
 4 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 4f401fc6a05d..52c69551aea4 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2423,12 +2423,14 @@ static int dr_interception(struct vcpu_svm *svm)
 		if (!kvm_require_dr(&svm->vcpu, dr - 16))
 			return 1;
 		val = kvm_register_read(&svm->vcpu, reg);
+		trace_kvm_dr_write(dr - 16, val);
 		kvm_set_dr(&svm->vcpu, dr - 16, val);
 	} else {
 		if (!kvm_require_dr(&svm->vcpu, dr))
 			return 1;
 		kvm_get_dr(&svm->vcpu, dr, &val);
 		kvm_register_write(&svm->vcpu, reg, val);
+		trace_kvm_dr_read(dr, val);
 	}
 
 	return kvm_skip_emulated_instruction(&svm->vcpu);
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index aef960f90f26..b3bf54405862 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -405,6 +405,33 @@ TRACE_EVENT(kvm_cr,
 #define trace_kvm_cr_read(cr, val)		trace_kvm_cr(0, cr, val)
 #define trace_kvm_cr_write(cr, val)		trace_kvm_cr(1, cr, val)
 
+/*
+ * Tracepoint for guest DR access.
+ */
+TRACE_EVENT(kvm_dr,
+	TP_PROTO(unsigned int rw, unsigned int dr, unsigned long val),
+	TP_ARGS(rw, dr, val),
+
+	TP_STRUCT__entry(
+		__field(	unsigned int,	rw		)
+		__field(	unsigned int,	dr		)
+		__field(	unsigned long,	val		)
+	),
+
+	TP_fast_assign(
+		__entry->rw		= rw;
+		__entry->dr		= dr;
+		__entry->val		= val;
+	),
+
+	TP_printk("dr_%s %x = 0x%lx",
+		  __entry->rw ? "write" : "read",
+		  __entry->dr, __entry->val)
+);
+
+#define trace_kvm_dr_read(dr, val)		trace_kvm_dr(0, dr, val)
+#define trace_kvm_dr_write(dr, val)		trace_kvm_dr(1, dr, val)
+
 TRACE_EVENT(kvm_pic_set_irq,
 	    TP_PROTO(__u8 chip, __u8 pin, __u8 elcr, __u8 imr, bool coalesced),
 	    TP_ARGS(chip, pin, elcr, imr, coalesced),
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4551a7e80ebc..f78fd297d51e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5091,10 +5091,16 @@ static int handle_dr(struct kvm_vcpu *vcpu)
 
 		if (kvm_get_dr(vcpu, dr, &val))
 			return 1;
+		trace_kvm_dr_read(dr, val);
 		kvm_register_write(vcpu, reg, val);
-	} else
-		if (kvm_set_dr(vcpu, dr, kvm_register_readl(vcpu, reg)))
+	} else {
+		unsigned long val;
+
+		val = kvm_register_readl(vcpu, reg);
+		trace_kvm_dr_write(dr, val);
+		if (kvm_set_dr(vcpu, dr, val))
 			return 1;
+	}
 
 	return kvm_skip_emulated_instruction(vcpu);
 }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c4015a43cc8a..68cb7b331324 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11153,6 +11153,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_page_fault);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_msr);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_cr);
+EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_dr);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_vmrun);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_vmexit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_vmexit_inject);
-- 
2.18.4