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

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Message-ID: <967c0a4f-c864-21ec-33f1-5e3943a42409@arm.com>
Date:   Tue, 28 Jun 2022 13:10:05 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Will Deacon <will@...nel.org>
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 6/27/22 16:31, Will Deacon wrote:
> 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

Hello Will,

I did go through the above mentioned thread, but could not understand (clear
enough) - what needs to be done. Could you please help summerize the problem
and possible solutions which I can start looking into. Thank you.

- Anshuman