Re: [PATCH] tests/qtest/migration: Restore include for postcopy

[Daniel P . Berrangé]

On Wed, Dec 18, 2024 at 12:12:11PM -0300, Fabiano Rosas wrote:
> Daniel P. Berrangé <berrange@redhat.com> writes:
> 
> > On Tue, Dec 17, 2024 at 04:47:39PM -0500, Peter Xu wrote:
> >> On Tue, Dec 17, 2024 at 06:22:01PM -0300, Fabiano Rosas wrote:
> >> > Commit 124a3c58b8 ("tests/qtest/migration: Move ufd_version_check to
> >> > utils") moved the ufd_version_check() function to another file but
> >> > failed to bring along the <sys/syscall> include, which is necessary to
> >> > pull in <asm/unistd.h> for __NR_userfaultd.
> >> > 
> >> > Restore the missing include.
> >> 
> >> Ohhhhhhh.. so postcopy tests will always be skipped as of now?  Maybe worth
> >> explicit mention that in the commit message if so, only when you merge.
> >> 
> >> > 
> >> > While here, remove the ifdef __linux__ that's redundant and fix a
> >> > couple of typos.
> >> > 
> >> > Fixes: 124a3c58b8 ("tests/qtest/migration: Move ufd_version_check to 
> >> > utils")
> >> > Signed-off-by: Fabiano Rosas <farosas@suse.de>
> >> 
> >> Reviewed-by: Peter Xu <peterx@redhat.com>
> >> 
> >> Maybe we don't need to be as careful on old kernels anymore especially in
> >> tests, because userfaultfd syscall existed for ~10 years. So if we want we
> >> can start requiring __NR_userfaultfd present for __linux__, then no way to
> >> miss such spot next time.
> >
> > Yes, I think that check is obsolete, based on our supported platforms
> > list. It would suffice to just check __linux__.
> 
> This breaks the cross builds. It seems the __NR_userfaultfd was actually
> stopping several archs from reaching ufd_version_check(). Since
> <sys/ioctl.h> is under HOST_X86_64, these new instances now fail to find
> the 'ioctl' symbol:
> 
> https://gitlab.com/farosas/qemu/-/pipelines/1594332399
> 
> Of course I could just include <sys/ioctl.h> unconditionally, but the
> fact that new code is not being built means the assumption that we can
> imply __NR_userfaultfd from __linux__ alone is not correct.

I think removing __NR_userfaultfd is still correct. The problem is that
the ufd_version_check code is wrapped in a conditional that is not the
same as the conditional that pulls in ioctl.h. That pre-existing bug
should be fixed regardless, and once that's done, removing __NR_userfaultfd
wouldn't be an issue.

With regards,
Daniel
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