Hi,
Please ignore this version as I messed up with the author information. I am
sending a V2 with the proper author name.
Thanks
Athira
> On 30-Mar-2020, at 5:08 PM, Athira Rajeev <atraj...@linux.vnet.ibm.com> wrote:
>
> "pmcregs_in_use" flag is part of lppaca (Virtual Process Area),
> which is used to indicate whether Performance Monitoring Unit (PMU) and
> PMU sprs are in-use and whether should it be saved/restored by
> hypervisor. ppc_set_pmu_inuse() is used to set/unset the VPA
> flag "pmcregs_in_use". "pmcregs_in_use" flag is set in
> "power_pmu_enable" via ppc_set_pmu_inuse(1) and it is unset
> when there are no active events (n_events == 0 condition).
>
> Patch here adds documentation on the ppc_set_pmu_inuse() usage.
>
> Signed-off-by: Madhavan Srinivasan <ma...@linux.ibm.com>
> Signed-off-by: Athira Rajeev <atraj...@linux.vnet.ibm.com>
> ---
> arch/powerpc/perf/core-book3s.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index 3086055..48bfdc9 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -1285,6 +1285,11 @@ static void power_pmu_enable(struct pmu *pmu)
> goto out;
>
> if (cpuhw->n_events == 0) {
> + /*
> + * Indicate PMU not in-use to Hypervisor.
> + * We end-up here via "ctx_sched_out()" from common code and
> + * "power_pmu_del()".
> + */
> ppc_set_pmu_inuse(0);
> goto out;
> }
> @@ -1341,6 +1346,11 @@ static void power_pmu_enable(struct pmu *pmu)
> * Write the new configuration to MMCR* with the freeze
> * bit set and set the hardware events to their initial values.
> * Then unfreeze the events.
> + * ppc_set_pmu_inuse(1): "power_pmu_enable" will unset the
> + * "pmcregs_in_use" flag when a previous profiling/sampling session
> + * is completed and un-setting of flag will notify the Hypervisor to
> + * drop save/restore of PMU sprs. Now that PMU need to be enabled, first
> + * set the "pmcregs_in_use" flag in VPA.
> */
> ppc_set_pmu_inuse(1);
> mtspr(SPRN_MMCRA, cpuhw->mmcr[2] & ~MMCRA_SAMPLE_ENABLE);
> --
> 1.8.3.1
>
