linux-kernel - Re: selftests/vm madv

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Date:   Fri, 15 Oct 2021 17:47:03 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: selftests/vm madv_populate.c test

On 15.10.21 17:45, Shuah Khan wrote:
> On 9/18/21 1:41 AM, David Hildenbrand wrote:
>> On 18.09.21 00:45, Shuah Khan wrote:
>>> Hi David,
>>>
>>> I am running into the following warning when try to build this test:
>>>
>>> madv_populate.c:334:2: warning: #warning "missing MADV_POPULATE_READ or MADV_POPULATE_WRITE definition" [-Wcpp]
>>>     334 | #warning "missing MADV_POPULATE_READ or MADV_POPULATE_WRITE definition"
>>>         |  ^~~~~~~
>>>
>>>
>>> I see that the following handling is in place. However there is no
>>> other information to explain why the check is necessary.
>>>
>>> #if defined(MADV_POPULATE_READ) && defined(MADV_POPULATE_WRITE)
>>>
>>> #else /* defined(MADV_POPULATE_READ) && defined(MADV_POPULATE_WRITE) */
>>>
>>> #warning "missing MADV_POPULATE_READ or MADV_POPULATE_WRITE definition"
>>>
>>> I do see these defined in:
>>>
>>> include/uapi/asm-generic/mman-common.h:#define MADV_POPULATE_READ       22
>>> include/uapi/asm-generic/mman-common.h:#define MADV_POPULATE_WRITE      23
>>>
>>> Is this the case of missing include from madv_populate.c?
>>
>> Hi Shuan,
>>
>> note that we're including "#include <sys/mman.h>", which in my
>> understanding maps to the version installed on your system instead
>> of the one in our build environment.ing.
>>
>> So as soon as you have a proper kernel + the proper headers installed
>> and try to build, it would pick up MADV_POPULATE_READ and
>> MADV_POPULATE_WRITE from the updated headers. That makes sense: you
>> annot run any MADV_POPULATE_READ/MADV_POPULATE_WRITE tests on a kernel
>> that doesn't support it.
>>
>> See vm/userfaultfd.c where we do something similar.
>>
> 
> Kselftest is for testing the kernel with kernel headers. That is the
> reason why there is the dependency on header install.
> 
>>
>> As soon as we have a proper environment, it seems to work just fine:
>>
>> Linux vm-0 5.15.0-0.rc1.20210915git3ca706c189db.13.fc36.x86_64 #1 SMP Thu Sep 16 11:32:54 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
>> [root@...0 linux]# cat /etc/redhat-release
>> Fedora release 36 (Rawhide)
> 
> This is a distro release. We don't want to have dependency on headers
> from the distro to run selftests. Hope this makes sense.
> 
> I still see this on my test system running Linux 5.15-rc5.

Did you also install Linux headers? I assume no, correct?

-- 
Thanks,

David / dhildenb