Re: [RFC 8/9] RISC-V: KVM: Implement perf support

Andrew Jones
2022-11-01T15:31:52Z

On Mon, Jul 18, 2022 at 10:02:04AM -0700, Atish Patra wrote:
> RISC-V SBI PMU & Sscofpmf ISA extension allows supporting perf in
> the virtualization enviornment as well. KVM implementation
> relies on SBI PMU extension for most of the part while traps

...relies on the SBI PMU extension for the most part while trapping
and emulating...

> & emulates the CSRs read for counter access.
>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---
> arch/riscv/kvm/vcpu_pmu.c | 318 ++++++++++++++++++++++++++++++++++++--
> 1 file changed, 301 insertions(+), 17 deletions(-)
>
> diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
> index 5434051f495d..278c261efad3 100644
> --- a/arch/riscv/kvm/vcpu_pmu.c
> +++ b/arch/riscv/kvm/vcpu_pmu.c
> @@ -11,9 +11,163 @@
> #include <linux/kvm_host.h>
> #include <linux/perf/riscv_pmu.h>
> #include <asm/csr.h>
> +#include <asm/bitops.h>
> #include <asm/kvm_vcpu_pmu.h>
> #include <linux/kvm_host.h>
>
> +#define get_event_type(x) ((x & SBI_PMU_EVENT_IDX_TYPE_MASK) >> 16)
> +#define get_event_code(x) (x & SBI_PMU_EVENT_IDX_CODE_MASK)
> +
> +static inline u64 pmu_get_sample_period(struct kvm_pmc *pmc)
> +{
> + u64 counter_val_mask = GENMASK(pmc->cinfo.width, 0);
> + u64 sample_period;
> +
> + if (!pmc->counter_val)
> + sample_period = counter_val_mask;
> + else
> + sample_period = pmc->counter_val & counter_val_mask;
> +
> + return sample_period;
> +}
> +
> +static u32 pmu_get_perf_event_type(unsigned long eidx)
> +{
> + enum sbi_pmu_event_type etype = get_event_type(eidx);
> + u32 type;
> +
> + if (etype == SBI_PMU_EVENT_TYPE_HW)
> + type = PERF_TYPE_HARDWARE;
> + else if (etype == SBI_PMU_EVENT_TYPE_CACHE)
> + type = PERF_TYPE_HW_CACHE;
> + else if (etype == SBI_PMU_EVENT_TYPE_RAW || etype == SBI_PMU_EVENT_TYPE_FW)
> + type = PERF_TYPE_RAW;
> + else
> + type = PERF_TYPE_MAX;
> +
> + return type;
> +}
> +
> +static inline bool pmu_is_fw_event(unsigned long eidx)
> +{
> + enum sbi_pmu_event_type etype = get_event_type(eidx);
> +
> + return (etype == SBI_PMU_EVENT_TYPE_FW) ? true : false;

return get_event_type(eidx) == SBI_PMU_EVENT_TYPE_FW;

> +}
> +
> +static void pmu_release_perf_event(struct kvm_pmc *pmc)
> +{
> + if (pmc->perf_event) {
> + perf_event_disable(pmc->perf_event);
> + perf_event_release_kernel(pmc->perf_event);
> + pmc->perf_event = NULL;
> + }
> +}
> +
> +static u64 pmu_get_perf_event_hw_config(u32 sbi_event_code)
> +{
> + /* SBI PMU HW event code is offset by 1 from perf hw event codes */
> + return (u64)sbi_event_code - 1;
> +}
> +
> +static u64 pmu_get_perf_event_cache_config(u32 sbi_event_code)
> +{
> + u64 config = U64_MAX;
> + unsigned int cache_type, cache_op, cache_result;
> +
> + /* All the cache event masks lie within 0xFF. No separate masking is necesssary */
> + cache_type = (sbi_event_code & SBI_PMU_EVENT_CACHE_ID_CODE_MASK) >> 3;
> + cache_op = (sbi_event_code & SBI_PMU_EVENT_CACHE_OP_ID_CODE_MASK) >> 1;
> + cache_result = sbi_event_code & SBI_PMU_EVENT_CACHE_RESULT_ID_CODE_MASK;
> +
> + if (cache_type >= PERF_COUNT_HW_CACHE_MAX ||
> + cache_op >= PERF_COUNT_HW_CACHE_OP_MAX ||
> + cache_result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
> + goto out;

No goto necessary

if (...)
return U64_MAX;
return cache_type | (cache_op << 8) | (cache_result << 16);

> + config = cache_type | (cache_op << 8) | (cache_result << 16);
> +out:
> + return config;
> +}
> +
> +static u64 pmu_get_perf_event_config(unsigned long eidx, uint64_t edata)
> +{
> + enum sbi_pmu_event_type etype = get_event_type(eidx);
> + u32 ecode = get_event_code(eidx);
> + u64 config = U64_MAX;
> +
> + if (etype == SBI_PMU_EVENT_TYPE_HW)
> + config = pmu_get_perf_event_hw_config(ecode);
> + else if (etype == SBI_PMU_EVENT_TYPE_CACHE)
> + config = pmu_get_perf_event_cache_config(ecode);
> + else if (etype == SBI_PMU_EVENT_TYPE_RAW)
> + config = edata & RISCV_PMU_RAW_EVENT_MASK;
> + else if ((etype == SBI_PMU_EVENT_TYPE_FW) && (ecode < SBI_PMU_FW_MAX))
> + config = (1ULL << 63) | ecode;
> +
> + return config;
> +}
> +
> +static int pmu_get_fixed_pmc_index(unsigned long eidx)
> +{
> + u32 etype = pmu_get_perf_event_type(eidx);
> + u32 ecode = get_event_code(eidx);
> + int ctr_idx;
> +
> + if (etype != SBI_PMU_EVENT_TYPE_HW)
> + return -EINVAL;
> +
> + if (ecode == SBI_PMU_HW_CPU_CYCLES)
> + ctr_idx = 0;
> + else if (ecode == SBI_PMU_HW_INSTRUCTIONS)
> + ctr_idx = 2;
> + else
> + return -EINVAL;
> +
> + return ctr_idx;
> +}
> +
> +static int pmu_get_programmable_pmc_index(struct kvm_pmu *kvpmu, unsigned long eidx,
> + unsigned long cbase, unsigned long cmask)
> +{
> + int ctr_idx = -1;
> + int i, pmc_idx;
> + int min, max;
> +
> + if (pmu_is_fw_event(eidx)) {
> + /* Firmware counters are mapped 1:1 starting from num_hw_ctrs for simplicity */
> + min = kvpmu->num_hw_ctrs;
> + max = min + kvpmu->num_fw_ctrs;
> + } else {
> + /* First 3 counters are reserved for fixed counters */
> + min = 3;
> + max = kvpmu->num_hw_ctrs;
> + }
> +
> + for_each_set_bit(i, &cmask, BITS_PER_LONG) {
> + pmc_idx = i + cbase;
> + if ((pmc_idx >= min && pmc_idx < max) &&
> + !test_bit(pmc_idx, kvpmu->used_pmc)) {
> + ctr_idx = pmc_idx;
> + break;
> + }
> + }
> +
> + return ctr_idx;
> +}
> +
> +static int pmu_get_pmc_index(struct kvm_pmu *pmu, unsigned long eidx,
> + unsigned long cbase, unsigned long cmask)
> +{
> + int ret;
> +
> + /* Fixed counters need to be have fixed mapping as they have different width */
> + ret = pmu_get_fixed_pmc_index(eidx);
> + if (ret >= 0)
> + return ret;
> +
> + return pmu_get_programmable_pmc_index(pmu, eidx, cbase, cmask);
> +}
> +
> int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
> unsigned long *out_val)
> {
> @@ -43,7 +197,6 @@ int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu, unsigned int csr_num,
>
> if (!kvpmu)
> return KVM_INSN_EXIT_TO_USER_SPACE;
> - //TODO: Should we check if vcpu pmu is initialized or not!
> if (wr_mask)
> return KVM_INSN_ILLEGAL_TRAP;
> cidx = csr_num - CSR_CYCLE;
> @@ -81,14 +234,62 @@ int kvm_riscv_vcpu_pmu_ctr_info(struct kvm_vcpu *vcpu, unsigned long cidx,
> int kvm_riscv_vcpu_pmu_ctr_start(struct kvm_vcpu *vcpu, unsigned long ctr_base,
> unsigned long ctr_mask, unsigned long flag, uint64_t ival)
> {
> - /* TODO */
> + struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> + int i, num_ctrs, pmc_index;
> + struct kvm_pmc *pmc;
> +
> + num_ctrs = kvpmu->num_fw_ctrs + kvpmu->num_hw_ctrs;
> + if (ctr_base + __fls(ctr_mask) >= num_ctrs)
> + return -EINVAL;
> +
> + /* Start the counters that have been configured and requested by the guest */
> + for_each_set_bit(i, &ctr_mask, RISCV_MAX_COUNTERS) {
> + pmc_index = i + ctr_base;
> + if (!test_bit(pmc_index, kvpmu->used_pmc))
> + continue;
> + pmc = &kvpmu->pmc[pmc_index];
> + if (flag & SBI_PMU_START_FLAG_SET_INIT_VALUE)
> + pmc->counter_val = ival;
> + if (pmc->perf_event) {
> + perf_event_period(pmc->perf_event, pmu_get_sample_period(pmc));
> + perf_event_enable(pmc->perf_event);
> + }

What about checking the "SBI_ERR_ALREADY_STARTED" condition?

> + }
> +
> return 0;
> }
>
> int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base,
> unsigned long ctr_mask, unsigned long flag)
> {
> - /* TODO */
> + struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> + int i, num_ctrs, pmc_index;
> + u64 enabled, running;
> + struct kvm_pmc *pmc;
> +
> + num_ctrs = kvpmu->num_fw_ctrs + kvpmu->num_hw_ctrs;
> + if ((ctr_base + __fls(ctr_mask)) >= num_ctrs)
> + return -EINVAL;
> +
> + /* Stop the counters that have been configured and requested by the guest */
> + for_each_set_bit(i, &ctr_mask, RISCV_MAX_COUNTERS) {
> + pmc_index = i + ctr_base;
> + if (!test_bit(pmc_index, kvpmu->used_pmc))
> + continue;
> + pmc = &kvpmu->pmc[pmc_index];
> + if (pmc->perf_event) {
> + /* Stop counting the counter */
> + perf_event_disable(pmc->perf_event);
> + if (flag & SBI_PMU_STOP_FLAG_RESET) {
> + /* Relase the counter if this is a reset request */
> + pmc->counter_val += perf_event_read_value(pmc->perf_event,
> + &enabled, &running);
> + pmu_release_perf_event(pmc);
> + clear_bit(pmc_index, kvpmu->used_pmc);
> + }

What about checking the "SBI_ERR_ALREADY_STOPPED" condition?

> + }
> + }
> +
> return 0;
> }
>
> @@ -96,14 +297,85 @@ int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba
> unsigned long ctr_mask, unsigned long flag,
> unsigned long eidx, uint64_t edata)
> {
> - /* TODO */
> - return 0;
> + struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> + struct perf_event *event;
> + struct perf_event_attr attr;
> + int num_ctrs, ctr_idx;
> + u32 etype = pmu_get_perf_event_type(eidx);
> + u64 config;
> + struct kvm_pmc *pmc;
> +
> + num_ctrs = kvpmu->num_fw_ctrs + kvpmu->num_hw_ctrs;
> + if ((etype == PERF_TYPE_MAX) || ((ctr_base + __fls(ctr_mask)) >= num_ctrs))

nit: Unnecessary ()

> + return -EINVAL;
> +
> + if (pmu_is_fw_event(eidx))
> + return -EOPNOTSUPP;

nit: need blank line here

> + /*
> + * SKIP_MATCH flag indicates the caller is aware of the assigned counter
> + * for this event. Just do a sanity check if it already marked used.
> + */
> + if (flag & SBI_PMU_CFG_FLAG_SKIP_MATCH) {
> + if (!test_bit(ctr_base, kvpmu->used_pmc))
> + return -EINVAL;
> + ctr_idx = ctr_base;
> + goto match_done;
> + }
> +
> + ctr_idx = pmu_get_pmc_index(kvpmu, eidx, ctr_base, ctr_mask);
> + if (ctr_idx < 0)
> + return -EOPNOTSUPP;
> +
> +match_done:
> + pmc = &kvpmu->pmc[ctr_idx];
> + pmu_release_perf_event(pmc);
> + pmc->idx = ctr_idx;
> +
> + config = pmu_get_perf_event_config(eidx, edata);
> + memset(&attr, 0, sizeof(struct perf_event_attr));
> + attr.type = etype;
> + attr.size = sizeof(attr);
> + attr.pinned = true;
> +
> + /*
> + * It should never reach here if the platform doesn't support sscofpmf extensio
> + * as mode filtering won't work without it.
> + */
> + attr.exclude_host = true;
> + attr.exclude_hv = true;
> + attr.exclude_user = flag & SBI_PMU_CFG_FLAG_SET_UINH ? 1 : 0;
> + attr.exclude_kernel = flag & SBI_PMU_CFG_FLAG_SET_SINH ? 1 : 0;

nit: can use !!(flag & SBI_PMU_CFG_FLAG_SET_UINH)

> + attr.config = config;
> + attr.config1 = RISCV_KVM_PMU_CONFIG1_GUEST_EVENTS;
> + if (flag & SBI_PMU_CFG_FLAG_CLEAR_VALUE) {
> + //TODO: Do we really want to clear the value in hardware counter
> + pmc->counter_val = 0;
> + }

nit: add blank line

> + /*
> + * Set the default sample_period for now. The guest specified value
> + * will be updated in the start call.
> + */
> + attr.sample_period = pmu_get_sample_period(pmc);
> +
> + event = perf_event_create_kernel_counter(&attr, -1, current, NULL, pmc);
> + if (IS_ERR(event)) {
> + pr_err("kvm pmu event creation failed event %pe for eidx %lx\n", event, eidx);
> + return -EOPNOTSUPP;
> + }
> +
> + set_bit(ctr_idx, kvpmu->used_pmc);
> + pmc->perf_event = event;
> + if (flag & SBI_PMU_CFG_FLAG_AUTO_START)
> + perf_event_enable(pmc->perf_event);
> +
> + return ctr_idx;
> }
>
> int kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
> {
> int i = 0, num_hw_ctrs, num_fw_ctrs, hpm_width;
> struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> + struct kvm_pmc *pmc;
>
> if (!kvpmu)
> return -EINVAL;
> @@ -120,6 +392,7 @@ int kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
> return -EINVAL;
> }
>
> + bitmap_zero(kvpmu->used_pmc, RISCV_MAX_COUNTERS);
> kvpmu->num_hw_ctrs = num_hw_ctrs;
> kvpmu->num_fw_ctrs = num_fw_ctrs;
> /*
> @@ -132,38 +405,49 @@ int kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
> /* TIME CSR shouldn't be read from perf interface */
> if (i == 1)
> continue;
> - kvpmu->pmc[i].idx = i;
> - kvpmu->pmc[i].vcpu = vcpu;
> + pmc = &kvpmu->pmc[i];

Better to introduce this with the patch that introduced this loop.

> + pmc->idx = i;
> + pmc->counter_val = 0;
> + pmc->vcpu = vcpu;
> if (i < kvpmu->num_hw_ctrs) {
> kvpmu->pmc[i].cinfo.type = SBI_PMU_CTR_TYPE_HW;
> if (i < 3)
> /* CY, IR counters */
> - kvpmu->pmc[i].cinfo.width = 63;
> + pmc->cinfo.width = 63;
> else
> - kvpmu->pmc[i].cinfo.width = hpm_width;
> + pmc->cinfo.width = hpm_width;
> /*
> * The CSR number doesn't have any relation with the logical
> * hardware counters. The CSR numbers are encoded sequentially
> * to avoid maintaining a map between the virtual counter
> * and CSR number.
> */
> - kvpmu->pmc[i].cinfo.csr = CSR_CYCLE + i;
> + pmc->cinfo.csr = CSR_CYCLE + i;
> } else {
> - kvpmu->pmc[i].cinfo.type = SBI_PMU_CTR_TYPE_FW;
> - kvpmu->pmc[i].cinfo.width = BITS_PER_LONG - 1;
> + pmc->cinfo.type = SBI_PMU_CTR_TYPE_FW;
> + pmc->cinfo.width = BITS_PER_LONG - 1;
> }
> }
>
> return 0;
> }
>
> -void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu)
> +void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu)
> {
> - /* TODO */
> + struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> + struct kvm_pmc *pmc;
> + int i;
> +
> + if (!kvpmu)
> + return;
> +
> + for_each_set_bit(i, kvpmu->used_pmc, RISCV_MAX_COUNTERS) {
> + pmc = &kvpmu->pmc[i];
> + pmu_release_perf_event(pmc);
> + }
> }
>
> -void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu)
> +void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu)
> {
> - /* TODO */
> + kvm_riscv_vcpu_pmu_deinit(vcpu);
> }
> -
> --
> 2.25.1
>

Thanks,
drew