linux-kernel - [PATCH 1/2] KVM: arm64: Trace values with kvm_sys

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Message-Id: <20250319-trace-v1-1-0fff03204efa@daynix.com>
Date: Wed, 19 Mar 2025 20:38:55 +0900
From: Akihiko Odaki <akihiko.odaki@...nix.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
 Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>, 
 Zenghui Yu <yuzenghui@...wei.com>, 
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, devel@...nix.com, 
 Akihiko Odaki <akihiko.odaki@...nix.com>
Subject: [PATCH 1/2] KVM: arm64: Trace values with kvm_sys_access

Tracing values written to or read from system registers.

Signed-off-by: Akihiko Odaki <akihiko.odaki@...nix.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