0001-perf-x86-amd-Do-not-touch-the-AMD64_EVENTSEL_HOSTONL.patchFrom 9f724a38754d3f99a1b332c11e72e9dd213289d7 Mon Sep 17 00:00:00 2001

From: Like Xu <redacted>

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 <redacted>
---
 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

The subject should be:

"perf/x86: Do not touch AMD64_EVENTSEL_HOSTONLY bit inside the guest"

Sorry for the noise.

On Tue, Jul 20 2021 at 11:28, Like Xu wrote:

The subject should be:

"perf/x86: Do not touch AMD64_EVENTSEL_HOSTONLY bit inside the guest"

Sorry for the noise.

Please resend proper.

Thanks,

        tglx