> On 24 Feb 2025, at 6:45 PM, Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> wrote:
>
> Update 'kvm-hv-pmu.c' to add five new perf-events mapped to the five
> Hostwide counters. Since these newly introduced perf events are at system
> wide scope and can be read from any L1-Lpar CPU, 'kvmppc_pmu' scope and
> capabilities are updated appropriately.
>
> Also introduce two new helpers. First is kvmppc_update_l0_stats() that uses
> the infrastructure introduced in previous patches to issues the
> H_GUEST_GET_STATE hcall L0-PowerVM to fetch guest-state-buffer holding the
> latest values of these counters which is then parsed and 'l0_stats'
> variable updated.
>
> Second helper is kvmppc_pmu_event_update() which is called from
> 'kvmppv_pmu' callbacks and uses kvmppc_update_l0_stats() to update
> 'l0_stats' and the update the 'struct perf_event's event-counter.
>
> Some minor updates to kvmppc_pmu_{add, del, read}() to remove some debug
> scaffolding code.
>
> Signed-off-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
> ---
> Changelog
>
> v3->v4:
> * Minor tweaks to patch description and code as its now being built as a
> separate kernel module.
>
> v2->v3:
> None
>
> v1->v2:
> None
> ---
> arch/powerpc/perf/kvm-hv-pmu.c | 92 +++++++++++++++++++++++++++++++++-
> 1 file changed, 91 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/perf/kvm-hv-pmu.c b/arch/powerpc/perf/kvm-hv-pmu.c
> index ed371454f7b5..274459bb32d6 100644
> --- a/arch/powerpc/perf/kvm-hv-pmu.c
> +++ b/arch/powerpc/perf/kvm-hv-pmu.c
> @@ -30,6 +30,11 @@
> #include "asm/guest-state-buffer.h"
>
> enum kvmppc_pmu_eventid {
> + KVMPPC_EVENT_HOST_HEAP,
> + KVMPPC_EVENT_HOST_HEAP_MAX,
> + KVMPPC_EVENT_HOST_PGTABLE,
> + KVMPPC_EVENT_HOST_PGTABLE_MAX,
> + KVMPPC_EVENT_HOST_PGTABLE_RECLAIM,
> KVMPPC_EVENT_MAX,
> };
>
> @@ -61,8 +66,14 @@ static DEFINE_SPINLOCK(lock_l0_stats);
> /* GSB related structs needed to talk to L0 */
> static struct kvmppc_gs_msg *gsm_l0_stats;
> static struct kvmppc_gs_buff *gsb_l0_stats;
> +static struct kvmppc_gs_parser gsp_l0_stats;
>
> static struct attribute *kvmppc_pmu_events_attr[] = {
> + KVMPPC_PMU_EVENT_ATTR(host_heap, KVMPPC_EVENT_HOST_HEAP),
> + KVMPPC_PMU_EVENT_ATTR(host_heap_max, KVMPPC_EVENT_HOST_HEAP_MAX),
> + KVMPPC_PMU_EVENT_ATTR(host_pagetable, KVMPPC_EVENT_HOST_PGTABLE),
> + KVMPPC_PMU_EVENT_ATTR(host_pagetable_max, KVMPPC_EVENT_HOST_PGTABLE_MAX),
> + KVMPPC_PMU_EVENT_ATTR(host_pagetable_reclaim, KVMPPC_EVENT_HOST_PGTABLE_RECLAIM),
> NULL,
> };
>
> @@ -71,7 +82,7 @@ static const struct attribute_group kvmppc_pmu_events_group = {
> .attrs = kvmppc_pmu_events_attr,
> };
>
> -PMU_FORMAT_ATTR(event, "config:0");
> +PMU_FORMAT_ATTR(event, "config:0-5");
> static struct attribute *kvmppc_pmu_format_attr[] = {
> &format_attr_event.attr,
> NULL,
> @@ -88,6 +99,79 @@ static const struct attribute_group *kvmppc_pmu_attr_groups[] = {
> NULL,
> };
>
> +/*
> + * Issue the hcall to get the L0-host stats.
> + * Should be called with l0-stat lock held
> + */
> +static int kvmppc_update_l0_stats(void)
> +{
> + int rc;
> +
> + /* With HOST_WIDE flags guestid and vcpuid will be ignored */
> + rc = kvmppc_gsb_recv(gsb_l0_stats, KVMPPC_GS_FLAGS_HOST_WIDE);
> + if (rc)
> + goto out;
> +
> + /* Parse the guest state buffer is successful */
> + rc = kvmppc_gse_parse(&gsp_l0_stats, gsb_l0_stats);
> + if (rc)
> + goto out;
> +
> + /* Update the l0 returned stats*/
> + memset(&l0_stats, 0, sizeof(l0_stats));
> + rc = kvmppc_gsm_refresh_info(gsm_l0_stats, gsb_l0_stats);
> +
> +out:
> + return rc;
> +}
> +
> +/* Update the value of the given perf_event */
> +static int kvmppc_pmu_event_update(struct perf_event *event)
> +{
> + int rc;
> + u64 curr_val, prev_val;
> + unsigned long flags;
> + unsigned int config = event->attr.config;
> +
> + /* Ensure no one else is modifying the l0_stats */
> + spin_lock_irqsave(&lock_l0_stats, flags);
> +
> + rc = kvmppc_update_l0_stats();
> + if (!rc) {
> + switch (config) {
> + case KVMPPC_EVENT_HOST_HEAP:
> + curr_val = l0_stats.guest_heap;
> + break;
> + case KVMPPC_EVENT_HOST_HEAP_MAX:
> + curr_val = l0_stats.guest_heap_max;
> + break;
> + case KVMPPC_EVENT_HOST_PGTABLE:
> + curr_val = l0_stats.guest_pgtable_size;
> + break;
> + case KVMPPC_EVENT_HOST_PGTABLE_MAX:
> + curr_val = l0_stats.guest_pgtable_size_max;
> + break;
> + case KVMPPC_EVENT_HOST_PGTABLE_RECLAIM:
> + curr_val = l0_stats.guest_pgtable_reclaim;
> + break;
> + default:
> + rc = -ENOENT;
> + break;
> + }
> + }
> +
> + spin_unlock_irqrestore(&lock_l0_stats, flags);
> +
> + /* If no error than update the perf event */
> + if (!rc) {
> + prev_val = local64_xchg(&event->hw.prev_count, curr_val);
> + if (curr_val > prev_val)
> + local64_add(curr_val - prev_val, &event->count);
> + }
> +
> + return rc;
> +}
> +
> static int kvmppc_pmu_event_init(struct perf_event *event)
> {
> unsigned int config = event->attr.config;
> @@ -110,15 +194,19 @@ static int kvmppc_pmu_event_init(struct perf_event *event)
>
> static void kvmppc_pmu_del(struct perf_event *event, int flags)
> {
> + /* Do nothing */
> }
If we don’t read the counter stats in “del” call back, we will loose the final count getting updated, right ?
Del callback needs to call kvmppc_pmu_read. Can you check the difference in count stats by calling kvmppc_pmu_read here ?
Thanks
Athira
>
> static int kvmppc_pmu_add(struct perf_event *event, int flags)
> {
> + if (flags & PERF_EF_START)
> + return kvmppc_pmu_event_update(event);
> return 0;
> }
>
> static void kvmppc_pmu_read(struct perf_event *event)
> {
> + kvmppc_pmu_event_update(event);
> }
>
> /* Return the size of the needed guest state buffer */
> @@ -302,6 +390,8 @@ static struct pmu kvmppc_pmu = {
> .read = kvmppc_pmu_read,
> .attr_groups = kvmppc_pmu_attr_groups,
> .type = -1,
> + .scope = PERF_PMU_SCOPE_SYS_WIDE,
> + .capabilities = PERF_PMU_CAP_NO_EXCLUDE | PERF_PMU_CAP_NO_INTERRUPT,
> };
>
> static int __init kvmppc_register_pmu(void)
> --
> 2.48.1
>
>
>
