linux-kernel - Re: [PATCH v2] perf/x86/amd: Don't touch the AMD64_EVENTSEL

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Date:   Wed, 4 Aug 2021 12:28:54 +0100
From:   Liam Merwick <Liam.Merwick@...cle.com>
To:     Like Xu <like.xu.linux@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Joerg Roedel <joerg.roedel@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, liam.merwick@...cle.com,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perf/x86/amd: Don't touch the AMD64_EVENTSEL_HOSTONLY
 bit inside the guest

On (08/02/21 15:08), Like Xu wrote:
> Date:   Mon,  2 Aug 2021 15:08:50 +0800
> From: Like Xu <like.xu.linux@...il.com>
> To: Peter Zijlstra <peterz@...radead.org>, Joerg Roedel
>  <joerg.roedel@....com>
> Cc: Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo
>  <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin
>  <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>,
>  Namhyung Kim <namhyung@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
>  Borislav Petkov <bp@...en8.de>, x86@...nel.org, "H . Peter Anvin"
>  <hpa@...or.com>, linux-perf-users@...r.kernel.org,
>  linux-kernel@...r.kernel.org
> Subject: [PATCH v2] perf/x86/amd: Don't touch the AMD64_EVENTSEL_HOSTONLY
>  bit inside the guest
> X-Mailer: git-send-email 2.32.0
> 
> From: Like Xu <likexu@...cent.com>
> 
> 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>
> Tested-by: Kim Phillips <kim.phillips@....com>

Reviewed-by: Liam Merwick <liam.merwick@...cle.com>
Tested-by: Liam Merwick <liam.merwick@...cle.com>
[ Patch applied to a 5.4 branch ]

Should it also include

Cc: stable@...r.kernel.org

Regards,
Liam

> ---
> v2: Add Fixes tag and Tested-by from Kim.
> v1: https://lore.kernel.org/lkml/20210720112605.63286-1-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 d6003e08b055..1c3ae954a230 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
>