linux-kernel - [PATCH v4 2/2] riscv: KVM: add basic support for host vs guest profiling

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Message-Id: <00342d535311eb0629b9ba4f1e457a48e2abee33.1728957131.git.zhouquan@iscas.ac.cn>
Date: Tue, 15 Oct 2024 10:58:37 +0800
From: zhouquan@...as.ac.cn
To: anup@...infault.org,
	ajones@...tanamicro.com,
	atishp@...shpatra.org,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	mark.rutland@....com,
	alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org
Cc: linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	kvm@...r.kernel.org,
	kvm-riscv@...ts.infradead.org,
	linux-perf-users@...r.kernel.org,
	Quan Zhou <zhouquan@...as.ac.cn>
Subject: [PATCH v4 2/2] riscv: KVM: add basic support for host vs guest profiling

From: Quan Zhou <zhouquan@...as.ac.cn>

For the information collected on the host side, we need to
identify which data originates from the guest and record
these events separately, this can be achieved by having
KVM register perf callbacks.

Signed-off-by: Quan Zhou <zhouquan@...as.ac.cn>
---
 arch/riscv/include/asm/kvm_host.h | 10 ++++++++++
 arch/riscv/kvm/Kconfig            |  1 +
 arch/riscv/kvm/main.c             | 12 ++++++++++--
 arch/riscv/kvm/vcpu.c             |  7 +++++++
 4 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 2e2254fd2a2a..35eab6e0f4ae 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -286,6 +286,16 @@ struct kvm_vcpu_arch {
 	} sta;
 };
 
+/*
+ * Returns true if a Performance Monitoring Interrupt (PMI), a.k.a. perf event,
+ * arrived in guest context.  For riscv, any event that arrives while a vCPU is
+ * loaded is considered to be "in guest".
+ */
+static inline bool kvm_arch_pmi_in_guest(struct kvm_vcpu *vcpu)
+{
+	return IS_ENABLED(CONFIG_GUEST_PERF_EVENTS) && !!vcpu;
+}
+
 static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 
 #define KVM_RISCV_GSTAGE_TLB_MIN_ORDER		12
diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
index 26d1727f0550..0c3cbb0915ff 100644
--- a/arch/riscv/kvm/Kconfig
+++ b/arch/riscv/kvm/Kconfig
@@ -32,6 +32,7 @@ config KVM
 	select KVM_XFER_TO_GUEST_WORK
 	select KVM_GENERIC_MMU_NOTIFIER
 	select SCHED_INFO
+	select GUEST_PERF_EVENTS if PERF_EVENTS
 	help
 	  Support hosting virtualized guest machines.
 
diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
index f3427f6de608..5682e338ae6d 100644
--- a/arch/riscv/kvm/main.c
+++ b/arch/riscv/kvm/main.c
@@ -51,6 +51,12 @@ void kvm_arch_disable_virtualization_cpu(void)
 	csr_write(CSR_HIDELEG, 0);
 }
 
+static void kvm_riscv_teardown(void)
+{
+	kvm_riscv_aia_exit();
+	kvm_unregister_perf_callbacks();
+}
+
 static int __init riscv_kvm_init(void)
 {
 	int rc;
@@ -105,9 +111,11 @@ static int __init riscv_kvm_init(void)
 		kvm_info("AIA available with %d guest external interrupts\n",
 			 kvm_riscv_aia_nr_hgei);
 
+	kvm_register_perf_callbacks(NULL);
+
 	rc = kvm_init(sizeof(struct kvm_vcpu), 0, THIS_MODULE);
 	if (rc) {
-		kvm_riscv_aia_exit();
+		kvm_riscv_teardown();
 		return rc;
 	}
 
@@ -117,7 +125,7 @@ module_init(riscv_kvm_init);
 
 static void __exit riscv_kvm_exit(void)
 {
-	kvm_riscv_aia_exit();
+	kvm_riscv_teardown();
 
 	kvm_exit();
 }
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 8d7d381737ee..e8ffb3456898 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -226,6 +226,13 @@ bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
 	return (vcpu->arch.guest_context.sstatus & SR_SPP) ? true : false;
 }
 
+#ifdef CONFIG_GUEST_PERF_EVENTS
+unsigned long kvm_arch_vcpu_get_ip(struct kvm_vcpu *vcpu)
+{
+	return vcpu->arch.guest_context.sepc;
+}
+#endif
+
 vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
 {
 	return VM_FAULT_SIGBUS;
-- 
2.34.1