Commit d1e7e602 authored by Stephane Eranian's avatar Stephane Eranian Committed by Ingo Molnar
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perf/x86/intel: Move regs->flags EXACT bit init 



This patch removes a redundant store on regs->flags introduced
by commit:

  71eb9ee9 ("perf/x86/intel: Fix linear IP of PEBS real_ip on Haswell and later CPUs")

We were clearing the PERF_EFLAGS_EXACT but it was overwritten by
regs->flags = pebs->flags later on.

The PERF_EFLAGS_EXACT is a software flag using bit 3 of regs->flags.
X86 marks this bit as Reserved. To make sure this bit is zero before
we do any IP processing, we clear it explicitly.

Patch also removes the following assignment:

	regs->flags = pebs->flags | (regs->flags & PERF_EFLAGS_VM);

Because there is no regs->flags to preserve anymore because
set_linear_ip() is not called until later.

Signed-off-by: default avatarStephane Eranian <eranian@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: kan.liang@intel.com
Link: http://lkml.kernel.org/r/1522909791-32498-1-git-send-email-eranian@google.com


[ Improve capitalization, punctuation and clarity of comments. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b89e7914

arch/x86/events/intel/ds.c

+24 −10
Original line number Diff line number Diff line
@@ -1153,7 +1153,6 @@ static void setup_pebs_sample_data(struct perf_event *event, 
	if (pebs == NULL)

		return;



	regs->flags &= ~PERF_EFLAGS_EXACT;

	sample_type = event->attr.sample_type;

	dsrc = sample_type & PERF_SAMPLE_DATA_SRC;
@@ -1197,7 +1196,13 @@ static void setup_pebs_sample_data(struct perf_event *event, 
	 * and PMI.

	 */

	*regs = *iregs;

	regs->flags = pebs->flags;



	/*

	 * Initialize regs_>flags from PEBS,

	 * Clear exact bit (which uses x86 EFLAGS Reserved bit 3),

	 * i.e., do not rely on it being zero:

	 */

	regs->flags = pebs->flags & ~PERF_EFLAGS_EXACT;



	if (sample_type & PERF_SAMPLE_REGS_INTR) {

		regs->ax = pebs->ax;
@@ -1217,10 +1222,6 @@ static void setup_pebs_sample_data(struct perf_event *event, 
			regs->sp = pebs->sp;

		}



		/*

		 * Preserve PERF_EFLAGS_VM from set_linear_ip().

		 */

		regs->flags = pebs->flags | (regs->flags & PERF_EFLAGS_VM);

#ifndef CONFIG_X86_32

		regs->r8 = pebs->r8;

		regs->r9 = pebs->r9;
@@ -1234,20 +1235,33 @@ static void setup_pebs_sample_data(struct perf_event *event, 
	}



	if (event->attr.precise_ip > 1) {

		/* Haswell and later have the eventing IP, so use it: */

		/*

		 * Haswell and later processors have an 'eventing IP'

		 * (real IP) which fixes the off-by-1 skid in hardware.

		 * Use it when precise_ip >= 2 :

		 */

		if (x86_pmu.intel_cap.pebs_format >= 2) {

			set_linear_ip(regs, pebs->real_ip);

			regs->flags |= PERF_EFLAGS_EXACT;

		} else {

			/* Otherwise use PEBS off-by-1 IP: */

			/* Otherwise, use PEBS off-by-1 IP: */

			set_linear_ip(regs, pebs->ip);



			/* ... and try to fix it up using the LBR entries: */

			/*

			 * With precise_ip >= 2, try to fix up the off-by-1 IP

			 * using the LBR. If successful, the fixup function

			 * corrects regs->ip and calls set_linear_ip() on regs:

			 */

			if (intel_pmu_pebs_fixup_ip(regs))

				regs->flags |= PERF_EFLAGS_EXACT;

		}

	} else

	} else {

		/*

		 * When precise_ip == 1, return the PEBS off-by-1 IP,

		 * no fixup attempted:

		 */

		set_linear_ip(regs, pebs->ip);

	}





	if ((sample_type & (PERF_SAMPLE_ADDR | PERF_SAMPLE_PHYS_ADDR)) &&

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