linux-kernel - Re: [PATCHv8 2/5] arm64: dts: qcom: msm8998: Add Coresight support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <281e3548-af53-f9a7-b9e4-813b448ab078@arm.com>
Date:   Thu, 18 Jul 2019 10:37:19 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     saiprakash.ranjan@...eaurora.org, gregkh@...uxfoundation.org,
        mathieu.poirier@...aro.org, leo.yan@...aro.org,
        alexander.shishkin@...ux.intel.com, mike.leach@...aro.org,
        robh+dt@...nel.org, bjorn.andersson@...aro.org,
        devicetree@...r.kernel.org, david.brown@...aro.org,
        mark.rutland@....com
Cc:     rnayak@...eaurora.org, vivek.gautam@...eaurora.org,
        sibis@...eaurora.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        marc.w.gonzalez@...e.fr
Subject: Re: [PATCHv8 2/5] arm64: dts: qcom: msm8998: Add Coresight support



On 18/07/2019 10:14, Sai Prakash Ranjan wrote:
> Hi Suzuki,
> 
> On 7/18/2019 1:58 PM, Suzuki K Poulose wrote:
>> Hi Sai,
>>
>>
>>           etr@...8000 {
>>> +            compatible = "arm,coresight-tmc", "arm,primecell";
>>> +            reg = <0x06048000 0x1000>;
>>> +
>>> +            clocks = <&rpmcc RPM_SMD_QDSS_CLK>, <&rpmcc
>>> RPM_SMD_QDSS_A_CLK>;
>>> +            clock-names = "apb_pclk", "atclk";
>>> +            arm,scatter-gather;
>>
>> Please could you confirm that you have tested the scatter-gather mode
>> with ETR ? Either via perf/sysfs. Please could you share your results ?
>> Unless verified
>> this is going to be fatal for the system.
>>
>> Similarly for other platforms.
>>
> 
> Yes I have tested with scatter-gather mode with ETR on all platforms
> which I have posted via sysfs(not perf) before on previous versions of
> this patch series and no issues were found. And I suppose this was
> discussed in v2 of this patch series [1].

Using the sysfs doesn't guarantee that the ETR actually uses SG mode, unless
the buffer size selected is > 1M, which is why I am more interested in the
perf usage. Alternatively you may configure a larger buffer size (say, 8MB) via:

echo 0x800000 > /sys/bus/coresight/.../tmc_etr0/buffer_size


> 
> As said in one of the series initially [1], QCOM msm downstream kernels
> have been using scatter gather mode and we haven't seen any fatal issues.
> 
> [1] https://patchwork.kernel.org/patch/10769535/

I haven't seen any test results there either.

Cheers
Suzuki