linux-kernel - [PATCH v8 7/8] KVM: arm64: Support trace filtering for guests

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Message-Id: <20241127100130.1162639-8-james.clark@linaro.org>
Date: Wed, 27 Nov 2024 10:01:24 +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 Brown <broonie@...nel.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	James Morse <james.morse@....com>,
	"Rob Herring (Arm)" <robh@...nel.org>,
	Shiqi Liu <shiqiliu@...t.edu.cn>,
	Fuad Tabba <tabba@...gle.com>,
	Raghavendra Rao Ananta <rananta@...gle.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v8 7/8] 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  |  5 +++++
 arch/arm64/kvm/debug.c             | 28 ++++++++++++++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/debug-sr.c |  1 +
 3 files changed, 34 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index ba251caa593b..cce07887551b 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -613,6 +613,7 @@ struct kvm_host_data {
 #define KVM_HOST_DATA_FLAG_HAS_SPE	0
 #define KVM_HOST_DATA_FLAG_HAS_TRF	1
 #define KVM_HOST_DATA_FLAG_TRBE_ENABLED	2
+#define KVM_HOST_DATA_FLAG_GUEST_FILTER	3
 	unsigned long flags;
 
 	struct kvm_cpu_context host_ctxt;
@@ -1387,6 +1388,8 @@ 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_set_trfcr(u64 guest_trfcr);
+void kvm_clear_trfcr(void);
 #else
 static inline void kvm_set_pmu_events(u64 set, struct perf_event_attr *attr) {}
 static inline void kvm_clr_pmu_events(u64 clr) {}
@@ -1396,6 +1399,8 @@ 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_set_trfcr(u64 guest_trfcr) {}
+static inline void kvm_clear_trfcr(void) {}
 #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 0c340ae7b5d1..9266f2776991 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -337,3 +337,31 @@ void kvm_disable_trbe(void)
 	host_data_clear_flag(TRBE_ENABLED);
 }
 EXPORT_SYMBOL_GPL(kvm_disable_trbe);
+
+void kvm_set_trfcr(u64 guest_trfcr)
+{
+	if (is_protected_kvm_enabled() || WARN_ON_ONCE(preemptible()))
+		return;
+
+	if (has_vhe())
+		write_sysreg_s(guest_trfcr, SYS_TRFCR_EL12);
+	else {
+		*host_data_ptr(guest_trfcr_el1) = guest_trfcr;
+		host_data_set_flag(GUEST_FILTER);
+	}
+}
+EXPORT_SYMBOL_GPL(kvm_set_trfcr);
+
+void kvm_clear_trfcr(void)
+{
+	if (is_protected_kvm_enabled() || WARN_ON_ONCE(preemptible()))
+		return;
+
+	if (has_vhe())
+		write_sysreg_s(0, SYS_TRFCR_EL12);
+	else {
+		*host_data_ptr(guest_trfcr_el1) = 0;
+		host_data_clear_flag(GUEST_FILTER);
+	}
+}
+EXPORT_SYMBOL_GPL(kvm_clear_trfcr);
diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
index 9479bee41801..7edee7ace433 100644
--- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c
+++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
@@ -67,6 +67,7 @@ static void __trace_do_switch(u64 *saved_trfcr, u64 new_trfcr)
 static bool __trace_needs_switch(void)
 {
 	return host_data_test_flag(TRBE_ENABLED) ||
+	       host_data_test_flag(GUEST_FILTER) ||
 	       (is_protected_kvm_enabled() && host_data_test_flag(HAS_TRF));
 }
 
-- 
2.34.1