2021-07-20 11:28:15

by Like Xu

Subject: [RESEND PATCH] perf/x86/amd: Do not touch the AMD64_EVENTSEL_HOSTONLY bit inside the guest

From: Like Xu <[email protected]>

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 <[email protected]>
---
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

2021-07-23 20:17:20

by Kim Phillips

Subject: Re: [RESEND PATCH] perf/x86/amd: Do not touch the AMD64_EVENTSEL_HOSTONLY bit inside the guest

+Tom L., Robert R.

On 7/20/21 6:26 AM, Like Xu wrote:
> From: Like Xu <[email protected]>
>
> 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 <[email protected]>
> ---

Tested-by: Kim Phillips <[email protected]>

If we were to add a Fixes: tag, would this be the right commit?:

commit 1018faa6cf23b256bf25919ef203cd7c129f06f2

Author: Joerg Roedel <[email protected]>

Date: Wed Feb 29 14:57:32 2012 +0100



perf/x86/kvm: Fix Host-Only/Guest-Only counting with SVM disabled


Thanks,

Kim

2021-07-29 13:51:29

by Like Xu

Subject: Re: [RESEND PATCH] perf/x86/amd: Do not touch the AMD64_EVENTSEL_HOSTONLY bit inside the guest

On 24/7/2021 4:16 am, Kim Phillips wrote:
> +Tom L., Robert R.
>
> On 7/20/21 6:26 AM, Like Xu wrote:
>> From: Like Xu <[email protected]>
>>
>> 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 <[email protected]>
>> ---
>
> Tested-by: Kim Phillips <[email protected]>

Thanks Kim.

Hi Peter, should I post a new version with the fix tag ?

>
> If we were to add a Fixes: tag, would this be the right commit?:
>
> commit 1018faa6cf23b256bf25919ef203cd7c129f06f2
>
> Author: Joerg Roedel <[email protected]>
>
> Date:   Wed Feb 29 14:57:32 2012 +0100
>
>
>
>     perf/x86/kvm: Fix Host-Only/Guest-Only counting with SVM disabled
>
>
> Thanks,
>
> Kim