linux-kernel - Re: [PATCH 0/8] arm64/perf: Enable branch stack sampling

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Date:   Mon, 27 Jun 2022 12:01:05 +0100
From:   Will Deacon <will@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        peterz@...radead.org, acme@...nel.org, mark.rutland@....com,
        Catalin Marinas <catalin.marinas@....com>,
        James Clark <james.clark@....com>,
        Rob Herring <robh@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 0/8] arm64/perf: Enable branch stack sampling

On Mon, Jun 13, 2022 at 03:31:11PM +0530, Anshuman Khandual wrote:
> This series enables perf branch stack sampling support on arm64 platform
> via a new arch feature called Branch Record Buffer Extension (BRBE). All
> relevant register definitions could be accessed here.
> 
> https://developer.arm.com/documentation/ddi0601/2021-12/AArch64-Registers
> 
> This series applies on v5.19-rc2 after the BRBE related perf ABI changes series
> (V6) that was posted earlier.
> 
> https://lore.kernel.org/linux-arm-kernel/20220610035101.424112-1-anshuman.khandual@arm.com/
> 
> Following issues remain inconclusive
> 
> - Jame's concerns regarding permission inadequacy related to perfmon_capable()
> - Jame's concerns regarding using perf_event_paranoid along with perfmon_capable()

afaict, the capability stuff remains unresolved with the SPE driver, so I'd
really like to see it fixed there first before we add more broken drivers.

https://lore.kernel.org/r/20220118100702.GB16547@willie-the-truck

Will