linux-kernel - Re: [PATCH V2 5/6] perf kvm report: Add guest

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Date:   Mon, 23 May 2022 08:54:51 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     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 V2 5/6] perf kvm report: Add guest_code support

On 5/17/2022 6:10 AM, Adrian Hunter wrote:
> Add an option to indicate that guest code can be found in the hypervisor
> process

Sorry for harping on this, but is it correct that this assumes that the 
code is still at the original location at decode time?

If yes we need some warnings for this, something like:

This only works when the code is still available in the riginal memory 
location at decode time. This is typically the case for kernel code 
(unless modules are unloaded). For user programs it only works as long 
as there is no memory pressure which might cause the memory to be 
reused. For dynamically generated (JITed) code it might be rather 
unreliable unless the hypervisor is SIGSTOPed during decoding.