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* [RESEND PATCH] perf/x86/amd: Do not touch the AMD64_EVENTSEL_HOSTONLY bit inside the guest
@ 2021-07-20 11:26 Like Xu
  2021-07-23 20:16 ` Kim Phillips
  0 siblings, 1 reply; 3+ messages in thread
From: Like Xu @ 2021-07-20 11:26 UTC (permalink / raw)
  To: Peter Zijlstra, Thomas Gleixner
  Cc: Ingo Molnar, Arnaldo Carvalho de Melo, Mark Rutland,
	Alexander Shishkin, Jiri Olsa, Namhyung Kim, Borislav Petkov,
	x86, H . Peter Anvin, linux-perf-users, linux-kernel

From: Like Xu <likexu@tencent.com>

If we use "perf record" in an AMD Milan guest, dmesg reports a #GP
warning from an unchecked MSR access error on MSR_F15H_PERF_CTLx:

[] unchecked MSR access error: WRMSR to 0xc0010200 (tried to write
0x0000020000110076) at rIP: 0xffffffff8106ddb4 (native_write_msr+0x4/0x20)
[] Call Trace:
[]  amd_pmu_disable_event+0x22/0x90
[]  x86_pmu_stop+0x4c/0xa0
[]  x86_pmu_del+0x3a/0x140

The AMD64_EVENTSEL_HOSTONLY bit is defined and used on the host,
while the guest perf driver should avoid such use.

Signed-off-by: Like Xu <likexu@tencent.com>
---
 arch/x86/events/perf_event.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 2bf1c7ea2758..795f4779023c 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1116,8 +1116,9 @@ void x86_pmu_stop(struct perf_event *event, int flags);
 static inline void x86_pmu_disable_event(struct perf_event *event)
 {
 	struct hw_perf_event *hwc = &event->hw;
+	u64 disable_mask = __this_cpu_read(cpu_hw_events.perf_ctr_virt_mask);
 
-	wrmsrl(hwc->config_base, hwc->config);
+	wrmsrl(hwc->config_base, hwc->config & ~disable_mask);
 
 	if (is_counter_pair(hwc))
 		wrmsrl(x86_pmu_config_addr(hwc->idx + 1), 0);
-- 
2.32.0


^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-07-29 13:49 UTC | newest]

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2021-07-20 11:26 [RESEND PATCH] perf/x86/amd: Do not touch the AMD64_EVENTSEL_HOSTONLY bit inside the guest Like Xu
2021-07-23 20:16 ` Kim Phillips
2021-07-29 13:49   ` Like Xu

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