Commit 7ef03438 authored by Sandipan Das's avatar Sandipan Das Committed by Peter Zijlstra
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perf/x86/amd/uncore: Use rdmsr if rdpmc is unavailable 



Not all uncore PMUs may support the use of the RDPMC instruction for
reading counters. In such cases, read the count from the corresponding
PERF_CTR register using the RDMSR instruction.

Signed-off-by: default avatarSandipan Das <sandipan.das@amd.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/e9d994e32a3fcb39fa59fcf43ab4260d11aba097.1696425185.git.sandipan.das@amd.com
parent 07888daa

arch/x86/events/amd/uncore.c

+13 −1
Original line number Diff line number Diff line
@@ -96,7 +96,16 @@ static void amd_uncore_read(struct perf_event *event) 
	 */



	prev = local64_read(&hwc->prev_count);



	/*

	 * Some uncore PMUs do not have RDPMC assignments. In such cases,

	 * read counts directly from the corresponding PERF_CTR.

	 */

	if (hwc->event_base_rdpmc < 0)

		rdmsrl(hwc->event_base, new);

	else

		rdpmcl(hwc->event_base_rdpmc, new);



	local64_set(&hwc->prev_count, new);

	delta = (new << COUNTER_SHIFT) - (prev << COUNTER_SHIFT);

	delta >>= COUNTER_SHIFT;
@@ -164,6 +173,9 @@ static int amd_uncore_add(struct perf_event *event, int flags) 
	hwc->event_base_rdpmc = pmu->rdpmc_base + hwc->idx;

	hwc->state = PERF_HES_UPTODATE | PERF_HES_STOPPED;



	if (pmu->rdpmc_base < 0)

		hwc->event_base_rdpmc = -1;



	if (flags & PERF_EF_START)

		event->pmu->start(event, PERF_EF_RELOAD);