[RFC 6/9] RISC-V: KVM: Add SBI PMU extension support

[Atish Patra]

SBI PMU extension allows KVM guests to configure/start/stop/query about
the PMU counters in virtualized enviornment as well.

In order to allow that, KVM implements the entire SBI PMU extension.

Signed-off-by: Atish Patra <atishp at rivosinc.com>
---
 arch/riscv/kvm/vcpu_sbi.c     | 11 +++++
 arch/riscv/kvm/vcpu_sbi_pmu.c | 81 +++++++++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+)
 create mode 100644 arch/riscv/kvm/vcpu_sbi_pmu.c

diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index d45e7da3f0d3..da9f7959340e 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -50,6 +50,16 @@ extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_hsm;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_experimental;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_vendor;
 
+#ifdef CONFIG_RISCV_PMU_SBI
+extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_pmu;
+#else
+static const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_pmu = {
+	.extid_start = -1UL,
+	.extid_end = -1UL,
+	.handler = NULL,
+};
+#endif
+
 static const struct kvm_vcpu_sbi_extension *sbi_ext[] = {
 	&vcpu_sbi_ext_v01,
 	&vcpu_sbi_ext_base,
@@ -58,6 +68,7 @@ static const struct kvm_vcpu_sbi_extension *sbi_ext[] = {
 	&vcpu_sbi_ext_rfence,
 	&vcpu_sbi_ext_srst,
 	&vcpu_sbi_ext_hsm,
+	&vcpu_sbi_ext_pmu,
 	&vcpu_sbi_ext_experimental,
 	&vcpu_sbi_ext_vendor,
 };
diff --git a/arch/riscv/kvm/vcpu_sbi_pmu.c b/arch/riscv/kvm/vcpu_sbi_pmu.c
new file mode 100644
index 000000000000..90c51a95d4f4
--- /dev/null
+++ b/arch/riscv/kvm/vcpu_sbi_pmu.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022 Rivos Inc
+ *
+ * Authors:
+ *     Atish Patra <atishp at rivosinc.com>
+ */
+
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/kvm_host.h>
+#include <asm/csr.h>
+#include <asm/sbi.h>
+#include <asm/kvm_vcpu_sbi.h>
+
+static int kvm_sbi_ext_pmu_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
+				   unsigned long *out_val,
+				   struct kvm_cpu_trap *utrap,
+				   bool *exit)
+{
+	int ret = -EOPNOTSUPP;
+	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
+	unsigned long funcid = cp->a6;
+	uint64_t temp;
+
+	switch (funcid) {
+	case SBI_EXT_PMU_NUM_COUNTERS:
+		ret = kvm_riscv_vcpu_pmu_num_ctrs(vcpu, out_val);
+		break;
+	case SBI_EXT_PMU_COUNTER_GET_INFO:
+		ret = kvm_riscv_vcpu_pmu_ctr_info(vcpu, cp->a0, out_val);
+		break;
+	case SBI_EXT_PMU_COUNTER_CFG_MATCH:
+#if defined(CONFIG_32BIT)
+		temp = ((uint64_t)cp->a5 << 32) | cp->a4;
+#else
+		temp = cp->a4;
+#endif
+		ret = kvm_riscv_vcpu_pmu_ctr_cfg_match(vcpu, cp->a0, cp->a1, cp->a2, cp->a3, temp);
+		if (ret >= 0) {
+			*out_val = ret;
+			ret = 0;
+		}
+		break;
+	case SBI_EXT_PMU_COUNTER_START:
+#if defined(CONFIG_32BIT)
+		temp = ((uint64_t)cp->a4 << 32) | cp->a3;
+#else
+		temp = cp->a3;
+#endif
+		ret = kvm_riscv_vcpu_pmu_ctr_start(vcpu, cp->a0, cp->a1, cp->a2, temp);
+		break;
+	case SBI_EXT_PMU_COUNTER_STOP:
+		ret = kvm_riscv_vcpu_pmu_ctr_stop(vcpu, cp->a0, cp->a1, cp->a2);
+		break;
+	case SBI_EXT_PMU_COUNTER_FW_READ:
+		ret = kvm_riscv_vcpu_pmu_ctr_read(vcpu, cp->a0, out_val);
+		break;
+	default:
+		ret = -EOPNOTSUPP;
+	}
+
+	return ret;
+}
+
+unsigned long kvm_sbi_ext_pmu_probe(unsigned long extid)
+{
+	/*
+	 * PMU Extension is only available to guests if privilege mode filtering
+	 * is available. Otherwise, guest will always count events while the
+	 * execution is in hypervisor mode.
+	 */
+	return riscv_isa_extension_available(NULL, SSCOFPMF);
+}
+
+const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_pmu = {
+	.extid_start = SBI_EXT_PMU,
+	.extid_end = SBI_EXT_PMU,
+	.handler = kvm_sbi_ext_pmu_handler,
+	.probe = kvm_sbi_ext_pmu_probe,
+};
-- 
2.25.1