Re: [PATCH 0/1] Update vfio-user module to the latest

[Michael S. Tsirkin]

On Fri, Aug 05, 2022 at 09:21:07AM +0200, Thomas Huth wrote:
> On 02/08/2022 12.00, Zhang, Chen wrote:
> > 
> > 
> > > -----Original Message-----
> > > From: Qemu-devel <qemu-devel-
> > > bounces+chen.zhang=intel.com@nongnu.org> On Behalf Of Jagannathan
> > > Raman
> > > Sent: Tuesday, August 2, 2022 9:24 AM
> > > To: qemu-devel@nongnu.org
> > > Cc: stefanha@gmail.com; berrange@redhat.com
> > > Subject: [PATCH 0/1] Update vfio-user module to the latest
> > > 
> > > Hi,
> > > 
> > > This patch updates the libvfio-user submodule to the latest.
> > 
> > Just a rough idea, why not depends on linux distribution for the 
> > libvfio-user.so?
> > It looks no libvfio-user packet in distribution's repo.
> > 
> > Hi Thomas/Daniel:
> > 
> > For the RFC QEMU user space eBPF support,
> > https://lore.kernel.org/all/20220617073630.535914-6-chen.zhang@intel.com/T/
> > Maybe introduce the libubpf.so as a subproject like libvfio-user.so is more 
> > appropriate?
> 
> Fair comment. I never noticed them before, but why do we have those
> submodules in the subprojects/ folder (libvduse, libvfio-user and
> libvhost-user)?

I don't think they are submodules are they?

> ... I don't think it's the job of QEMU to ship libraries
> that a user might want to use for a certain feature, so could we please
> remove those submodules again?

Why not?  Fundamentally I don't see why would libvhost-user be less
important to users than e.g. qemu-img or qemu-bridge-helper. There's no
rule saying we can only ship a single binary.

> If someone wants to use this, they can
> compile the libraries on their own or help their favorite distribution to
> ship them as packages.
> 
>  Thomas

I can speak for libvhost-user at least, the main reason is simple - QEMU
uses it - to be more precise, QEMU tests use it ATM, but there are also
ideas to implement the device side of virtio inside a VM and that will
use it more directly.  Same developers are working on both qemu and
libvhost-user parts.  So I don't think there is much interest in first
splitting it out then jumping through hoops to get it back.

But there are more reasons - for example, if an application
links against libvhost-user, then it's a good idea
to update libvhost-user and qemu together - they have
been tested together and are known to work well.

I suspect the same applies to other probjects in this area
but I'm not sure.

-- 
MST