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Message-ID: <df56f04b-cb25-5a47-ffef-b2e2ee0f6b74@intel.com>
Date:   Fri, 13 May 2022 18:14:49 +0300
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Subject: Re: [PATCH 6/6] perf intel-pt: Add guest_code support
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To:     Andi Kleen <ak@linux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>, Leo Yan <leo.yan@linaro.org>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        kvm@vger.kernel.org
References: <20220513090237.10444-1-adrian.hunter@intel.com>
 <20220513090237.10444-7-adrian.hunter@intel.com>
 <875ym9h4mt.fsf@linux.intel.com>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
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On 13/05/22 17:46, Andi Kleen wrote:
> Adrian Hunter <adrian.hunter@intel.com> writes:
> 
>> A common case for KVM test programs is that the guest object code can be
>> found in the hypervisor process (i.e. the test program running on the
>> host). To support that, a new option "--guest-code" has been added in
>> previous patches.
>>
>> In this patch, add support also to Intel PT.
>>
>> In particular, ensure guest_code thread is set up before attempting to
>> walk object code or synthesize samples.
> 
> Can you make it clear in the documentation what parts runs on the host
> and what parts on the guest? 

That is up to the test program.  All the host thread maps are
copied, so perf tools doesn't have to know.

> 
> I'm still not fully sure how it exactly finds the code on the host,
> how is the code transferred?

I don't know.  From a quick look at the code in
tools/testing/selftests/kvm/lib/kvm_util.c it seems to be using
KVM_SET_USER_MEMORY_REGION IOCTL.

> 
> Other than that more support for this use case is very useful.
> 
> -Andi