linux-kernel - Re: [PATCH 6/6] perf intel-pt: Add guest

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Message-ID: <871qwxgv1e.fsf@linux.intel.com>
Date:   Fri, 13 May 2022 11:13:49 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>, Leo Yan <leo.yan@...aro.org>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 6/6] perf intel-pt: Add guest_code support

Adrian Hunter <adrian.hunter@...el.com> writes:
>> 
>> 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.

Okay so it assumes that the pages with code on the guest are still intact: that is
you cannot quit the traced program, or at least not do something that would
fill it with other data?. Is that correct?

It sounds like with that restriction it's more useful for kernel traces.

-Andi