From: "Liang, Kan" <kan.liang@linux.intel.com>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: Stephane Eranian <eranian@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>
Subject: Re: [perf] perf_fuzzer causes unchecked MSR access error
Date: Thu, 4 Mar 2021 14:33:17 -0500 [thread overview]
Message-ID: <473aff30-5e4f-394f-1c75-9bae66e37bbc@linux.intel.com> (raw)
In-Reply-To: <a8cebd2-a0fe-2ade-30d6-d592b3423db@maine.edu>
On 3/3/2021 3:22 PM, Vince Weaver wrote:
> On Wed, 3 Mar 2021, Liang, Kan wrote:
>
>> We never use bit 58. It should be a new issue.
Actually, KVM uses it. They create a fake event called VLBR_EVENT, which
uses bit 58. It's introduced from the commit 097e4311cda9 ("perf/x86:
Add constraint to create guest LBR event without hw counter").
Since it's a fake event, it doesn't support PEBS. Perf should reject it
if it sets the precise_ip.
The below patch should fix the MSR access error.
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 5bac48d..1ea3c67 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3659,6 +3659,10 @@ static int intel_pmu_hw_config(struct perf_event
*event)
return ret;
if (event->attr.precise_ip) {
+
+ if ((event->attr.config & INTEL_ARCH_EVENT_MASK) ==
INTEL_FIXED_VLBR_EVENT)
+ return -EINVAL;
+
if (!(event->attr.freq || (event->attr.wakeup_events &&
!event->attr.watermark))) {
event->hw.flags |= PERF_X86_EVENT_AUTO_RELOAD;
if (!(event->attr.sample_type &
Thanks,
Kan
prev parent reply other threads:[~2021-03-04 19:35 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-28 14:25 [perf] perf_fuzzer causes crash in intel_pmu_drain_pebs_nhm() Vince Weaver
2021-01-28 19:49 ` Vince Weaver
2021-02-11 14:53 ` Peter Zijlstra
2021-02-11 21:37 ` Liang, Kan
2021-02-11 22:14 ` Vince Weaver
2021-02-25 20:15 ` Liang, Kan
2021-03-01 13:20 ` Liang, Kan
2021-03-02 5:29 ` Vince Weaver
2021-03-03 18:16 ` [perf] perf_fuzzer causes unchecked MSR access error Vince Weaver
2021-03-03 19:28 ` Stephane Eranian
2021-03-03 20:00 ` Liang, Kan
2021-03-03 20:22 ` Vince Weaver
2021-03-04 19:33 ` Liang, Kan [this message]
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