linux-kernel - [PATCH v9 6/7] KVM: arm64: Support trace filtering for guests

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Message-Id: <20250106142446.628923-7-james.clark@linaro.org>
Date: Mon,  6 Jan 2025 14:24:41 +0000
From: James Clark <james.clark@...aro.org>
To: maz@...nel.org,
	kvmarm@...ts.linux.dev,
	oliver.upton@...ux.dev,
	suzuki.poulose@....com,
	coresight@...ts.linaro.org
Cc: James Clark <james.clark@...aro.org>,
	Joey Gouly <joey.gouly@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Mike Leach <mike.leach@...aro.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Mark Rutland <mark.rutland@....com>,
	Shiqi Liu <shiqiliu@...t.edu.cn>,
	Mark Brown <broonie@...nel.org>,
	James Morse <james.morse@....com>,
	Anshuman Khandual <anshuman.khandual@....com>,
	"Rob Herring (Arm)" <robh@...nel.org>,
	Raghavendra Rao Ananta <rananta@...gle.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v9 6/7] KVM: arm64: Support trace filtering for guests

For nVHE, switch the filter value in and out if the Coresight driver
asks for it. This will support filters for guests when sinks other than
TRBE are used.

For VHE, just write the filter directly to TRFCR_EL1 where trace can be
used even with TRBE sinks.

Signed-off-by: James Clark <james.clark@...aro.org>
---
 arch/arm64/include/asm/kvm_host.h |  2 ++
 arch/arm64/kvm/debug.c            | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 8fdc7b6efc79..7cfa024de4e3 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1396,6 +1396,7 @@ void kvm_clr_pmu_events(u64 clr);
 bool kvm_set_pmuserenr(u64 val);
 void kvm_enable_trbe(void);
 void kvm_disable_trbe(void);
+void kvm_tracing_set_el1_configuration(u64 trfcr_while_in_guest);
 #else
 static inline void kvm_set_pmu_events(u64 set, struct perf_event_attr *attr) {}
 static inline void kvm_clr_pmu_events(u64 clr) {}
@@ -1405,6 +1406,7 @@ static inline bool kvm_set_pmuserenr(u64 val)
 }
 static inline void kvm_enable_trbe(void) {}
 static inline void kvm_disable_trbe(void) {}
+static inline void kvm_tracing_set_el1_configuration(u64 trfcr_while_in_guest) {}
 #endif
 
 void kvm_vcpu_load_vhe(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 92a24adadb0e..0e4c805e7e89 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -245,3 +245,21 @@ void kvm_disable_trbe(void)
 	host_data_clear_flag(TRBE_ENABLED);
 }
 EXPORT_SYMBOL_GPL(kvm_disable_trbe);
+
+void kvm_tracing_set_el1_configuration(u64 trfcr_while_in_guest)
+{
+	if (is_protected_kvm_enabled() || WARN_ON_ONCE(preemptible()))
+		return;
+
+	if (has_vhe()) {
+		write_sysreg_s(trfcr_while_in_guest, SYS_TRFCR_EL12);
+		return;
+	}
+
+	*host_data_ptr(trfcr_while_in_guest) = trfcr_while_in_guest;
+	if (read_sysreg_s(SYS_TRFCR_EL1) != trfcr_while_in_guest)
+		host_data_set_flag(EL1_TRACING_CONFIGURED);
+	else
+		host_data_clear_flag(EL1_TRACING_CONFIGURED);
+}
+EXPORT_SYMBOL_GPL(kvm_tracing_set_el1_configuration);
-- 
2.34.1