linux-kernel - [PATCH 5.4 77/85] perf/x86/amd: Dont touch the AMD64_EVENTSEL

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Message-Id: <20210810172950.834994078@linuxfoundation.org>
Date:   Tue, 10 Aug 2021 19:30:50 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Like Xu <likexu@...cent.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Liam Merwick <liam.merwick@...cle.com>,
        Kim Phillips <kim.phillips@....com>
Subject: [PATCH 5.4 77/85] perf/x86/amd: Dont touch the AMD64_EVENTSEL_HOSTONLY bit inside the guest

From: Like Xu <likexu@...cent.com>

commit df51fe7ea1c1c2c3bfdb81279712fdd2e4ea6c27 upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/events/perf_event.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -852,9 +852,10 @@ void x86_pmu_stop(struct perf_event *eve
 
 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);
 }
 
 void x86_pmu_enable_event(struct perf_event *event);