[PATCH 4.9 22/30] perf/x86/amd: Dont touch the AMD64_EVENTSEL_HOSTONLY bit inside the guest

Greg Kroah-Hartman
2021-08-13T15:10:18Z

From: Like Xu <likexu@tencent.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@tencent.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Tested-by: Kim Phillips <kim.phillips@amd.com>
Tested-by: Liam Merwick <liam.merwick@oracle.com>
Link: https://lkml.kernel.org/r/20210802070850.35295-1-likexu@tencent.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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
@@ -771,9 +771,10 @@ 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);