Re: [PATCH 2/2] Allow building vhost-user in BSD

[Daniel P . Berrangé]

On Wed, Mar 02, 2022 at 06:38:07PM +0100, Philippe Mathieu-Daudé wrote:
> On 2/3/22 18:31, Sergio Lopez wrote:
> > On Wed, Mar 02, 2022 at 06:18:59PM +0100, Philippe Mathieu-Daudé wrote:
> > > On 2/3/22 18:10, Paolo Bonzini wrote:
> > > > On 3/2/22 12:36, Sergio Lopez wrote:
> > > > > With the possibility of using pipefd as a replacement on operating
> > > > > systems that doesn't support eventfd, vhost-user can also work on BSD
> > > > > systems.
> > > > > 
> > > > > This change allows enabling vhost-user on BSD platforms too and
> > > > > makes libvhost_user (which still depends on eventfd) a linux-only
> > > > > feature.
> > > > > 
> > > > > Signed-off-by: Sergio Lopez <slp@redhat.com>
> > > > 
> > > > I would just check for !windows.
> > > 
> > > What about Darwin / Haiku / Illumnos?
> > 
> > It should work on every system providing pipe() or pipe2(), so I guess
> > Paolo's right, every platform except Windows. FWIW, I already tested
> > it with Darwin.
> 
> Wow, nice.
> 
> So maybe simply check for pipe/pipe2 rather than !windows?

NB that would make the check more fragile.

We already use pipe/pipe2 without checking for it, because its
usage is confined to oslib-posix.c and we know all POSIX
OS have it. There is no impl at all of qemu_pipe in oslib-win.c
and the declaration is masked out too in the header file.

Thus if we check for pipe2 and windows did ever implement it,
then we would actually break the windows build due to qemu_pipe
not existing. 

IOW, checking !windows matches our logic for picking oslib-posix.c
in builds and so is better than checking for pipe directly.

Regards,
Daniel
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