Commit 20b279dd authored Sep 13, 2012 by Peter Zijlstra Committed by Arnaldo Carvalho de Melo Oct 16, 2012

perf: Require exclude_guest to use PEBS - kernel side enforcement



Intel PEBS in VT-x context uses the DS address as a guest linear
address, even though its programmed by the host as a host linear
address. This either results in guest memory corruption and or the
hardware faulting and 'crashing' the virtual machine.  Therefore we have
to disable PEBS on VT-x enter and re-enable on VT-x exit, enforcing a
strict exclude_guest.

This patch enforces exclude_guest kernel side.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Robert Richter <robert.richter@amd.com>
Link: http://lkml.kernel.org/r/1347569955-54626-3-git-send-email-dsahern@gmail.com


Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 1342798c

arch/x86/kernel/cpu/perf_event.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -338,6 +338,9 @@ int x86_setup_perfctr(struct perf_event *event)
		/* BTS is currently only allowed for user-mode. */
		if (!attr->exclude_kernel)
		return -EOPNOTSUPP;

		if (!attr->exclude_guest)
		return -EOPNOTSUPP;
		}

		hwc->config \|= config;
		@@ -380,6 +383,9 @@ int x86_pmu_hw_config(struct perf_event *event)
		if (event->attr.precise_ip) {
		int precise = 0;

		if (!event->attr.exclude_guest)
		return -EOPNOTSUPP;

		/* Support for constant skid */
		if (x86_pmu.pebs_active && !x86_pmu.pebs_broken) {
		precise++;