[PATCH 0/2] KVM: arm64: A few trace additions

[PATCH 0/2] KVM: arm64: A few trace additions

[Akihiko Odaki]

These are tracepoints I added during recent debugging. I hope they are
useful for others too.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
Akihiko Odaki (2):
      KVM: arm64: Trace values with kvm_sys_access
      KVM: arm64: Trace SMC in a way similar to HVC

 arch/arm64/kvm/handle_exit.c       |  3 +++
 arch/arm64/kvm/sys_regs.c          | 24 ++++++++++++++----------
 arch/arm64/kvm/trace_handle_exit.h | 26 ++++++++++++++++++++++++--
 3 files changed, 41 insertions(+), 12 deletions(-)
---
base-commit: 8098cf067a7aae92a4f293df03964bf8474faca1
change-id: 20250319-trace-80cb8d39de2e

Best regards,
-- 
Akihiko Odaki <akihiko.odaki@daynix.com>

[PATCH 1/2] KVM: arm64: Trace values with kvm_sys_access

[Akihiko Odaki]

Tracing values written to or read from system registers.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 arch/arm64/kvm/sys_regs.c          | 24 ++++++++++++++----------
 arch/arm64/kvm/trace_handle_exit.h |  6 ++++--
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 14f66c7a4545..362e2758d101 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -3994,23 +3994,27 @@ static void perform_access(struct kvm_vcpu *vcpu,
 			   struct sys_reg_params *params,
 			   const struct sys_reg_desc *r)
 {
-	trace_kvm_sys_access(*vcpu_pc(vcpu), params, r);
+	bool skip;
 
 	/* Check for regs disabled by runtime config */
 	if (sysreg_hidden(vcpu, r)) {
 		kvm_inject_undefined(vcpu);
-		return;
+		skip = false;
+	} else {
+		/*
+		 * Not having an accessor means that we have configured a trap
+		 * that we don't know how to handle. This certainly qualifies
+		 * as a gross bug that should be fixed right away.
+		 */
+		BUG_ON(!r->access);
+
+		/* Skip instruction if instructed so */
+		skip = r->access(vcpu, params, r);
 	}
 
-	/*
-	 * Not having an accessor means that we have configured a trap
-	 * that we don't know how to handle. This certainly qualifies
-	 * as a gross bug that should be fixed right away.
-	 */
-	BUG_ON(!r->access);
+	trace_kvm_sys_access(*vcpu_pc(vcpu), params, r);
 
-	/* Skip instruction if instructed so */
-	if (likely(r->access(vcpu, params, r)))
+	if (likely(skip))
 		kvm_incr_pc(vcpu);
 }
 
diff --git a/arch/arm64/kvm/trace_handle_exit.h b/arch/arm64/kvm/trace_handle_exit.h
index f85415db7713..b0308d95304d 100644
--- a/arch/arm64/kvm/trace_handle_exit.h
+++ b/arch/arm64/kvm/trace_handle_exit.h
@@ -88,6 +88,7 @@ TRACE_EVENT(kvm_sys_access,
 
 	TP_STRUCT__entry(
 		__field(unsigned long,			vcpu_pc)
+		__field(u64,				regval)
 		__field(bool,				is_write)
 		__field(const char *,			name)
 		__field(u8,				Op0)
@@ -99,6 +100,7 @@ TRACE_EVENT(kvm_sys_access,
 
 	TP_fast_assign(
 		__entry->vcpu_pc = vcpu_pc;
+		__entry->regval = params->regval;
 		__entry->is_write = params->is_write;
 		__entry->name = reg->name;
 		__entry->Op0 = reg->Op0;
@@ -109,10 +111,10 @@ TRACE_EVENT(kvm_sys_access,
 		__entry->Op2 = reg->Op2;
 	),
 
-	TP_printk("PC: %lx %s (%d,%d,%d,%d,%d) %s",
+	TP_printk("PC: %lx %s (%d,%d,%d,%d,%d) %llx %s",
 		  __entry->vcpu_pc, __entry->name ?: "UNKN",
 		  __entry->Op0, __entry->Op1, __entry->CRn,
-		  __entry->CRm, __entry->Op2,
+		  __entry->CRm, __entry->Op2, __entry->regval,
 		  __entry->is_write ? "write" : "read")
 );
 

-- 
2.48.1

[PATCH 2/2] KVM: arm64: Trace SMC in a way similar to HVC

[Akihiko Odaki]

KVM handles SMCCC calls from virtual EL2 that use the SMC instruction
since commit bd36b1a9eb5a ("KVM: arm64: nv: Handle SMCs taken from
virtual EL2"). Copy the tracepoint for HVC to the SMC handler to trace
SMCCC calls whether they come from either HVC or SMC.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 arch/arm64/kvm/handle_exit.c       |  3 +++
 arch/arm64/kvm/trace_handle_exit.h | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 512d152233ff..087880b645be 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -55,6 +55,9 @@ static int handle_hvc(struct kvm_vcpu *vcpu)
 
 static int handle_smc(struct kvm_vcpu *vcpu)
 {
+	trace_kvm_smc_arm64(*vcpu_pc(vcpu), vcpu_get_reg(vcpu, 0),
+			    kvm_vcpu_hvc_get_imm(vcpu));
+
 	/*
 	 * Forward this trapped smc instruction to the virtual EL2 if
 	 * the guest has asked for it.
diff --git a/arch/arm64/kvm/trace_handle_exit.h b/arch/arm64/kvm/trace_handle_exit.h
index b0308d95304d..a3a0e0a46c60 100644
--- a/arch/arm64/kvm/trace_handle_exit.h
+++ b/arch/arm64/kvm/trace_handle_exit.h
@@ -46,6 +46,26 @@ TRACE_EVENT(kvm_hvc_arm64,
 		  __entry->vcpu_pc, __entry->r0, __entry->imm)
 );
 
+TRACE_EVENT(kvm_smc_arm64,
+	TP_PROTO(unsigned long vcpu_pc, unsigned long r0, unsigned long imm),
+	TP_ARGS(vcpu_pc, r0, imm),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, vcpu_pc)
+		__field(unsigned long, r0)
+		__field(unsigned long, imm)
+	),
+
+	TP_fast_assign(
+		__entry->vcpu_pc = vcpu_pc;
+		__entry->r0 = r0;
+		__entry->imm = imm;
+	),
+
+	TP_printk("SMC at 0x%016lx (r0: 0x%016lx, imm: 0x%lx)",
+		  __entry->vcpu_pc, __entry->r0, __entry->imm)
+);
+
 /*
  * The dreg32 name is a leftover from a distant past. This will really
  * output a 64bit value...

-- 
2.48.1