linux-kernel - Re: hw_breakpoint unit test failures with various architectures/platforms in qemu

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Message-ID: <a937b183-32bd-4a92-bc20-57319205b4eb@roeck-us.net>
Date: Mon, 4 Mar 2024 13:17:52 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Marco Elver <elver@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Dmitry Vyukov
 <dvyukov@...gle.com>, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Linux ARM <linux-arm-kernel@...ts.infradead.org>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Huacai Chen <chenhuacai@...nel.org>,
 loongarch@...ts.linux.dev
Subject: Re: hw_breakpoint unit test failures with various
 architectures/platforms in qemu

On 3/4/24 12:34, Marco Elver wrote:
> On Mon, 4 Mar 2024 at 19:12, Guenter Roeck <linux@...ck-us.net> wrote:
>>
>> Hi,
>>
>> I see a number of failures and tracebacks when running the hw_breakpoint
>> unit tests on various architectures in qemu. Some examples are below.
>>
>> Is this a potential problem with the unit tests, with the hardware,
>> or with the qemu emulation of that hardware ?
> 
> The test is testing the accounting logic (allocating/deallocating HW
> breakpoints), not actually using the breakpoints. That requires that
> the architecture reports the correct number of HW breakpoints
> available. It looks like it's not doing that.
> 
>> In other words, is it worthwhile to look into this further, or would
>> it make more sense to just disable those tests if they fail on a
>> given hardware/platform ?
> 
> It's an arch bug:
> https://lore.kernel.org/lkml/Ytl9L0Zn1PVuL1cB@FVFF77S0Q05N.cambridge.arm.com/
> 
> Back then we decided to leave the test as-is, given it's reporting an
> actual issue. However, since then nothing has changed and the test
> continues to exist as a reminder the arch code needs fixing. I suspect
> none of us have the time to get to that soon, so we can either leave
> things as is, or skip the test on all the broken architectures.
> 

Thanks a lot for the update and reference. I'll just skip the tests
for now and maybe check once in a while if something changed.

Thanks,
Guenter