linux-kernel - Re: [PATCH v2 2/4] perf tools: Use dynamic register set for Dwarf unwind

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Date:   Wed, 18 May 2022 22:00:56 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     James Clark <james.clark@....com>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        broonie@...nel.org, acme@...nel.org, german.gomez@....com,
        mathieu.poirier@...aro.org, john.garry@...wei.com,
        Will Deacon <will@...nel.org>,
        Mike Leach <mike.leach@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/4] perf tools: Use dynamic register set for Dwarf
 unwind

On Wed, May 18, 2022 at 02:25:38PM +0100, James Clark wrote:
> 
> 
> On 17/05/2022 12:03, Leo Yan wrote:
> > On Tue, May 17, 2022 at 11:20:03AM +0100, James Clark wrote:
> >> Architectures can detect availability of extra registers at
> >> runtime so use this more complete set for unwinding. This
> >> will include the VG register on arm64 in a later commit.
> >>
> >> If the function isn't implemented then PERF_REGS_MASK is
> >> returned and there is no change.
> >>
> >> Signed-off-by: James Clark <james.clark@....com>
> > 
> > This patch looks good to me:
> > Reviewed-by: Leo Yan <leo.yan@...aro.org>
> > 
> > Just curious, do you think should update the test (e.g.
> > arch/arm64/tests/dwarf-unwind.c) to use arch__user_reg_mask()?
> 
> I don't think so because the normal set of registers is manually
> loaded in tools/perf/arch/arm64/tests/regs_load.S so it wouldn't
> include this pseudo register. Also there is no SVE in the call
> chain of the test so it would never have an effect.
> 
> I could add a new test for SVE, but it depends on getting the
> libunwind changes through first so will have to come later.

It makes sense to add new SVE test later, thanks for clarification.

So this patch series looks good for me.

Leo