linux-kernel - [tip: perf/urgent] perf/x86/amd: Don't touch the AMD64_EVENTSEL

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Date:   Thu, 05 Aug 2021 09:34:28 -0000
From:   "tip-bot2 for Like Xu" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Like Xu <likexu@...cent.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Liam Merwick <liam.merwick@...cle.com>,
        Kim Phillips <kim.phillips@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/urgent] perf/x86/amd: Don't touch the
 AMD64_EVENTSEL_HOSTONLY bit inside the guest

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     df51fe7ea1c1c2c3bfdb81279712fdd2e4ea6c27
Gitweb:        https://git.kernel.org/tip/df51fe7ea1c1c2c3bfdb81279712fdd2e4ea6c27
Author:        Like Xu <likexu@...cent.com>
AuthorDate:    Mon, 02 Aug 2021 15:08:50 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 04 Aug 2021 15:16:34 +02:00

perf/x86/amd: Don't touch the AMD64_EVENTSEL_HOSTONLY bit inside the guest

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.

Fixes: 1018faa6cf23 ("perf/x86/kvm: Fix Host-Only/Guest-Only counting with SVM disabled")
Signed-off-by: Like Xu <likexu@...cent.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Liam Merwick <liam.merwick@...cle.com>
Tested-by: Kim Phillips <kim.phillips@....com>
Tested-by: Liam Merwick <liam.merwick@...cle.com>
Link: https://lkml.kernel.org/r/20210802070850.35295-1-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 2bf1c7e..2938c90 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1115,9 +1115,10 @@ void x86_pmu_stop(struct perf_event *event, int flags);
 
 static inline void x86_pmu_disable_event(struct perf_event *event)
 {
+	u64 disable_mask = __this_cpu_read(cpu_hw_events.perf_ctr_virt_mask);
 	struct hw_perf_event *hwc = &event->hw;
 
-	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);