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Subject[tip:perf/urgent] perf: Require exclude_guest to use PEBS - kernel side enforcement
Commit-ID:  20b279ddb38ca42f8863cec07b4d45ec24589f13
Gitweb: http://git.kernel.org/tip/20b279ddb38ca42f8863cec07b4d45ec24589f13
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 13 Sep 2012 14:59:14 -0600
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 16 Oct 2012 12:43:58 -0300

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>
---
arch/x86/kernel/cpu/perf_event.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 915b876..3373f84 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -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++;

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