Re: [PATCH v5 08/14] RISC-V: KVM: Add SBI PMU extension support

[Conor Dooley <conor@kernel.org>]

On 5 February 2023 02:15:09 GMT+01:00, Atish Patra <atishp@rivosinc.com> wrote:
>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.
>
>Reviewed-by: Anup Patel <anup@brainfault.org>
>Signed-off-by: Atish Patra <atishp@rivosinc.com>

Hey Atish,
CI is still complaining about something in this patch:
https://gist.github.com/conor-pwbot/8f8d6a60a65b0b44d96c9c3b220e3efd

I'm without a laptop this weekend, so apologies for
the lack of investigation as to whether there's a
reason for it.

Cheers,
Conor.


>---
> arch/riscv/kvm/Makefile       |  2 +-
> arch/riscv/kvm/vcpu_sbi.c     | 11 +++++
> arch/riscv/kvm/vcpu_sbi_pmu.c | 87 +++++++++++++++++++++++++++++++++++
> 3 files changed, 99 insertions(+), 1 deletion(-)
> create mode 100644 arch/riscv/kvm/vcpu_sbi_pmu.c
>
>diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
>index 5de1053..278e97c 100644
>--- a/arch/riscv/kvm/Makefile
>+++ b/arch/riscv/kvm/Makefile
>@@ -25,4 +25,4 @@ kvm-y += vcpu_sbi_base.o
> kvm-y += vcpu_sbi_replace.o
> kvm-y += vcpu_sbi_hsm.o
> kvm-y += vcpu_timer.o
>-kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o
>+kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o vcpu_sbi_pmu.o
>diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
>index fe2897e..15fde15 100644
>--- a/arch/riscv/kvm/vcpu_sbi.c
>+++ b/arch/riscv/kvm/vcpu_sbi.c
>@@ -20,6 +20,16 @@ static const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_v01 = {
> };
> #endif
> 
>+#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,
>@@ -28,6 +38,7 @@ 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 0000000..9fdc1e1
>--- /dev/null
>+++ b/arch/riscv/kvm/vcpu_sbi_pmu.c
>@@ -0,0 +1,87 @@
>+// SPDX-License-Identifier: GPL-2.0
>+/*
>+ * Copyright (c) 2023 Rivos Inc
>+ *
>+ * Authors:
>+ *     Atish Patra <atishp@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,
>+				   struct kvm_vcpu_sbi_return *retdata)
>+{
>+	int ret = 0;
>+	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
>+	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
>+	unsigned long funcid = cp->a6;
>+	u64 temp;
>+
>+	/* Return not supported if PMU is not initialized */
>+	if (!kvpmu->init_done) {
>+		retdata->err_val = SBI_ERR_NOT_SUPPORTED;
>+		return 0;
>+	}
>+
>+	switch (funcid) {
>+	case SBI_EXT_PMU_NUM_COUNTERS:
>+		ret = kvm_riscv_vcpu_pmu_num_ctrs(vcpu, retdata);
>+		break;
>+	case SBI_EXT_PMU_COUNTER_GET_INFO:
>+		ret = kvm_riscv_vcpu_pmu_ctr_info(vcpu, cp->a0, retdata);
>+		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
>+		/*
>+		 * This can fail if perf core framework fails to create an event.
>+		 * Forward the error to userspace because it's an error happened
>+		 * within the host kernel. The other option would be to convert
>+		 * this an SBI error and forward to the guest.
>+		 */
>+		ret = kvm_riscv_vcpu_pmu_ctr_cfg_match(vcpu, cp->a0, cp->a1,
>+						       cp->a2, cp->a3, temp, retdata);
>+		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, retdata);
>+		break;
>+	case SBI_EXT_PMU_COUNTER_STOP:
>+		ret = kvm_riscv_vcpu_pmu_ctr_stop(vcpu, cp->a0, cp->a1, cp->a2, retdata);
>+		break;
>+	case SBI_EXT_PMU_COUNTER_FW_READ:
>+		ret = kvm_riscv_vcpu_pmu_ctr_read(vcpu, cp->a0, retdata);
>+		break;
>+	default:
>+		retdata->err_val = SBI_ERR_NOT_SUPPORTED;
>+	}
>+
>+	return ret;
>+}
>+
>+static unsigned long kvm_sbi_ext_pmu_probe(struct kvm_vcpu *vcpu)
>+{
>+	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
>+
>+	return kvpmu->init_done;
>+}
>+
>+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,
>+};