Commit ee368428 authored by Alexander Shishkin's avatar Alexander Shishkin Committed by Ingo Molnar
Browse files

perf/x86/intel/pt: Handle VMX better 



Since commit:

  1c5ac21a ("perf/x86/intel/pt: Don't die on VMXON")

... PT events depend on re-scheduling to get enabled after a VMX session
has taken place. This is, in particular, a problem for CPU context events,
which don't normally get re-scheduled, unless there is a reason.

This patch changes the VMX handling so that PT event gets re-enabled
when VMX root mode exits.

Also, notify the user when there's a gap in PT data due to VMX root
mode by flagging AUX records as partial.

In combination with vmm_exclusive=0 parameter of the kvm_intel driver,
this will result in trace gaps only for the duration of the guest's
timeslices.

Signed-off-by: default avatarAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20170220133352.17995-5-alexander.shishkin@linux.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ae0c2d99

arch/x86/events/intel/pt.c

+21 −17
Original line number Diff line number Diff line
@@ -411,6 +411,7 @@ static u64 pt_config_filters(struct perf_event *event) 


static void pt_config(struct perf_event *event)

{

	struct pt *pt = this_cpu_ptr(&pt_ctx);

	u64 reg;



	if (!event->hw.itrace_started) {
@@ -429,11 +430,15 @@ static void pt_config(struct perf_event *event) 
	reg |= (event->attr.config & PT_CONFIG_MASK);



	event->hw.config = reg;

	if (READ_ONCE(pt->vmx_on))

		perf_aux_output_flag(&pt->handle, PERF_AUX_FLAG_PARTIAL);

	else

		wrmsrl(MSR_IA32_RTIT_CTL, reg);

}



static void pt_config_stop(struct perf_event *event)

{

	struct pt *pt = this_cpu_ptr(&pt_ctx);

	u64 ctl = READ_ONCE(event->hw.config);



	/* may be already stopped by a PMI */
@@ -441,6 +446,7 @@ static void pt_config_stop(struct perf_event *event) 
		return;



	ctl &= ~RTIT_CTL_TRACEEN;

	if (!READ_ONCE(pt->vmx_on))

		wrmsrl(MSR_IA32_RTIT_CTL, ctl);



	WRITE_ONCE(event->hw.config, ctl);
@@ -1174,12 +1180,6 @@ void intel_pt_interrupt(void) 
	if (!READ_ONCE(pt->handle_nmi))

		return;



	/*

	 * If VMX is on and PT does not support it, don't touch anything.

	 */

	if (READ_ONCE(pt->vmx_on))

		return;



	if (!event)

		return;
@@ -1239,12 +1239,19 @@ void intel_pt_handle_vmx(int on) 
	local_irq_save(flags);

	WRITE_ONCE(pt->vmx_on, on);



	if (on) {

		/* prevent pt_config_stop() from writing RTIT_CTL */

	/*

	 * If an AUX transaction is in progress, it will contain

	 * gap(s), so flag it PARTIAL to inform the user.

	 */

	event = pt->handle.event;

	if (event)

			event->hw.config = 0;

	}

		perf_aux_output_flag(&pt->handle,

		                     PERF_AUX_FLAG_PARTIAL);



	/* Turn PTs back on */

	if (!on && event)

		wrmsrl(MSR_IA32_RTIT_CTL, event->hw.config);



	local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(intel_pt_handle_vmx);
@@ -1259,9 +1266,6 @@ static void pt_event_start(struct perf_event *event, int mode) 
	struct pt *pt = this_cpu_ptr(&pt_ctx);

	struct pt_buffer *buf;



	if (READ_ONCE(pt->vmx_on))

		return;



	buf = perf_aux_output_begin(&pt->handle, event);

	if (!buf)

		goto fail_stop;

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