Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: u14/qyfGAN1M6+KdpO1le6oggWkQdMz52bnjheWVsa2pXwDd8QSXQgZwVXAG4u8Oe3N1zGd8Lt
 wdwCn+Bp3rxw==
IronPort-SDR: qHt8VwgY50FkTckdc70a2iHnvd96zGZJpY0l7Echlm93Wf7ZwKzbLKs+ZtKDEAKg1J22lRNLT/
 u+dbZ7R33RXg==
Subject: Re: [PATCH v1 2/2] perf/core: Fake regs for leaked kernel samples
To:     "Jin, Yao" <yao.jin@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>
Cc:     mingo@redhat.com, oleg@redhat.com, acme@kernel.org,
        jolsa@kernel.org, Linux-kernel@vger.kernel.org, ak@linux.intel.com,
        kan.liang@intel.com, yao.jin@intel.com,
        alexander.shishkin@linux.intel.com, mark.rutland@arm.com
References: <20200731025617.16243-1-yao.jin@linux.intel.com>
 <20200731025617.16243-2-yao.jin@linux.intel.com>
 <20200804114900.GI2657@hirez.programming.kicks-ass.net>
 <4c958d61-11a7-9f3e-9e7d-d733270144a1@linux.intel.com>
 <20200805124454.GP2657@hirez.programming.kicks-ass.net>
 <797aa4de-c618-f340-ad7b-cef38c96b035@linux.intel.com>
 <56957a58-6292-e075-8c30-6230450e3518@linux.intel.com>
 <20200811075924.GU3982@worktop.programming.kicks-ass.net>
 <dbc68bbf-b1a8-77ab-c89c-2d890a0382cc@linux.intel.com>
 <20200811084548.GW3982@worktop.programming.kicks-ass.net>
 <8bedaac0-2db1-b59c-581f-62f6d7a31c48@linux.intel.com>
From:   Like Xu <like.xu@linux.intel.com>
Organization: Intel OTC
Message-ID: <aa38dc24-4496-2d26-071e-26e9fbc3dbd4@linux.intel.com>
Date:   Wed, 12 Aug 2020 15:25:03 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101
 Thunderbird/68.11.0
MIME-Version: 1.0
In-Reply-To: <8bedaac0-2db1-b59c-581f-62f6d7a31c48@linux.intel.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2020/8/12 11:52, Jin, Yao wrote:
> Hi Peter,
> 
> On 8/11/2020 4:45 PM, Peter Zijlstra wrote:
>> On Tue, Aug 11, 2020 at 04:31:10PM +0800, Jin, Yao wrote:
>>> Hi Peter,
>>>
>>> On 8/11/2020 3:59 PM, Peter Zijlstra wrote:
>>>> On Tue, Aug 11, 2020 at 03:50:43PM +0800, Jin, Yao wrote:
>>>>> Could I post v2 which basically refers to your patch but removes some
>>>>> conditions since I see some issues in test if we use these conditions.
>>>>>
>>>>>    1. Remove '!event->attr.exclude_hv || !event->attr.exclude_host ||
>>>>>       !event->attr.exclude_guest' at the entry of sanitize_sample_regs().
>>>>>
>>>>>    2. Remove '!attr.exclude_hv || !attr.exclude_host || 
>>>>> !attr.exclude_guest'
>>>>>       at the perf_event_open syscall entry.
>>>>
>>>> exclude_host, maybe -- due to the dodgy semantics of it, but the others
>>>> should definitely be there.
>>>>
>>>
>>> exclude_guest and exclude_hv are tricky too.
>>>
>>> If we do 'perf record -e cycles:u' in both host and guest, we can see:
>>>
>>> event->attr.exclude_guest = 0
>>>
>>> thus sanitize_sample_regs() returns regs directly even if exclude_kernel 
>>> = 1.
>>>
>>> And in guest, exclude_hv = 0, it's out of my expectation too.
>>
>> I'm confused, how can 'perf record -e cycles:u' _ever_ have
>> exclude_guest=0, exclude_hv=0 ? That simply makes no sense and is utterly
>> broken.
>>
>> You explicitly ask for userspace-only, reporting hypervisor or guest
>> events is a straight up bug.

Guest events = guest user-space events + guest kernel-space events.

Some perf users on the host may only want to count guest user space events.

>>
> 
> If we run 'perf record -e cycles:u',
> 
> 1. On host, exclude_guest = 0 and exclude_hv = 1
> 
> perf tool doesn't specially set 'exclude_guest' when it parses the 'u' 
> modifier. I agree that can be improved. I will post a perf tool patch to 
> fix that.
> 
> 2. On guest, exclude_guest = 0 and exclude_hv = 0.
> 
> For exclude_hv = 0, it looks like a bug but x86 doesn't use exclude_hv. But 
> yes, we should fix that.
> 
> CC Like Xu <like.xu@linux.intel.com>.
> 
> Thanks
> Jin Yao