linux-kernel - [PATCH v2 4/6] arm64: KVM: Add interface to set guest value for TRFCR register

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Date:   Thu,  5 Oct 2023 13:57:52 +0100
From:   James Clark <james.clark@....com>
To:     coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.linux.dev, broonie@...nel.org, maz@...nel.org,
        suzuki.poulose@....com
Cc:     James Clark <james.clark@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Rob Herring <robh@...nel.org>,
        Jintack Lim <jintack.lim@...aro.org>,
        Akihiko Odaki <akihiko.odaki@...nix.com>,
        Fuad Tabba <tabba@...gle.com>, Joey Gouly <joey.gouly@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 4/6] arm64: KVM: Add interface to set guest value for TRFCR register

Add an interface for the Coresight driver to use to set the value of the
TRFCR register for the guest. This register controls the exclude
settings for trace at different exception levels, and is used to
honor the exclude_host and exclude_guest parameters from the Perf
session. This will be used to later write TRFCR_EL1 on nVHE at guest
switch. For VHE, TRFCR_EL1 is written immediately. Because guest writes
to the register are trapped, the value will persist and can't be
modified.

The settings must be copied to the vCPU before each run in the same
way that PMU events are because the per-cpu struct isn't accessible in
protected mode.

Now that both guest and host values are saved, rename trfcr_el1 to
host_trfcr_el1 to make it clear that's the value that should be restored
on return to the host.

Signed-off-by: James Clark <james.clark@....com>
---
 arch/arm64/include/asm/kvm_host.h |  3 +++
 arch/arm64/kvm/arm.c              |  1 +
 arch/arm64/kvm/debug.c            | 26 ++++++++++++++++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index b5200f199692..8f2b4ec8ea61 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1123,6 +1123,8 @@ void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu);
 void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr);
 void kvm_clr_pmu_events(u32 clr);
 bool kvm_set_pmuserenr(u64 val);
+void kvm_etm_set_guest_trfcr(u64 trfcr_guest);
+void kvm_etm_update_vcpu_events(struct kvm_vcpu *vcpu);
 #else
 static inline void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr) {}
 static inline void kvm_clr_pmu_events(u32 clr) {}
@@ -1130,6 +1132,7 @@ static inline bool kvm_set_pmuserenr(u64 val)
 {
 	return false;
 }
+static inline void kvm_etm_set_guest_trfcr(u64 trfcr_guest) {}
 #endif
 
 void kvm_vcpu_load_sysregs_vhe(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 78b0970eb8e6..22fab356b88f 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1012,6 +1012,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		kvm_vgic_flush_hwstate(vcpu);
 
 		kvm_pmu_update_vcpu_events(vcpu);
+		kvm_etm_update_vcpu_events(vcpu);
 
 		/*
 		 * Ensure we set mode to IN_GUEST_MODE after we disable
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 6a1bad1a921b..19e722359154 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -23,6 +23,12 @@
 
 static DEFINE_PER_CPU(u64, mdcr_el2);
 
+/*
+ * Per CPU value for TRFCR that should be applied to any guest vcpu that may
+ * run on that core in the future.
+ */
+static DEFINE_PER_CPU(u64, guest_trfcr);
+
 /**
  * save/restore_guest_debug_regs
  *
@@ -342,3 +348,23 @@ void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu)
 	vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_SPE);
 	vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRFCR);
 }
+
+void kvm_etm_set_guest_trfcr(u64 trfcr_guest)
+{
+	if (has_vhe())
+		write_sysreg_s(trfcr_guest, SYS_TRFCR_EL12);
+	else
+		*this_cpu_ptr(&guest_trfcr) = trfcr_guest;
+}
+EXPORT_SYMBOL_GPL(kvm_etm_set_guest_trfcr);
+
+/*
+ * Updates the vcpu's view of the etm events for this cpu. Must be
+ * called before every vcpu run after disabling interrupts, to ensure
+ * that an interrupt cannot fire and update the structure.
+ */
+void kvm_etm_update_vcpu_events(struct kvm_vcpu *vcpu)
+{
+	if (!has_vhe() && vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRFCR))
+		ctxt_sys_reg(&vcpu->arch.ctxt, TRFCR_EL1) = *this_cpu_ptr(&guest_trfcr);
+}
-- 
2.34.1