RE: [RFC PATCH 01/12] configure: Add iovisor/ubpf project as a submodule for QEMU

["Zhang, Chen" <chen.zhang@intel.com>]

> -----Original Message-----
> From: Thomas Huth <thuth@redhat.com>
> Sent: Monday, June 20, 2022 4:47 PM
> To: Daniel P. Berrangé <berrange@redhat.com>; Zhang, Chen
> <chen.zhang@intel.com>
> Cc: Jason Wang <jasowang@redhat.com>; qemu-dev <qemu-
> devel@nongnu.org>; Paolo Bonzini <pbonzini@redhat.com>; Eduardo
> Habkost <eduardo@habkost.net>; Eric Blake <eblake@redhat.com>; Markus
> Armbruster <armbru@redhat.com>; Peter Maydell
> <peter.maydell@linaro.org>; Laurent Vivier <lvivier@redhat.com>; Yuri
> Benditovich <yuri.benditovich@daynix.com>; Andrew Melnychenko
> <andrew@daynix.com>
> Subject: Re: [RFC PATCH 01/12] configure: Add iovisor/ubpf project as a
> submodule for QEMU
> 
> On 20/06/2022 10.11, Daniel P. Berrangé wrote:
> > On Mon, Jun 20, 2022 at 05:59:06AM +0000, Zhang, Chen wrote:
> >>
> >>
> >>> -----Original Message-----
> >>> From: Daniel P. Berrangé <berrange@redhat.com>
> >>> Sent: Friday, June 17, 2022 4:05 PM
> >>> To: Zhang, Chen <chen.zhang@intel.com>
> >>> Cc: Jason Wang <jasowang@redhat.com>; qemu-dev <qemu-
> >>> devel@nongnu.org>; Paolo Bonzini <pbonzini@redhat.com>; Eduardo
> >>> Habkost <eduardo@habkost.net>; Eric Blake <eblake@redhat.com>;
> >>> Markus Armbruster <armbru@redhat.com>; Peter Maydell
> >>> <peter.maydell@linaro.org>; Thomas Huth <thuth@redhat.com>;
> Laurent
> >>> Vivier <lvivier@redhat.com>; Yuri Benditovich
> >>> <yuri.benditovich@daynix.com>; Andrew Melnychenko
> >>> <andrew@daynix.com>
> >>> Subject: Re: [RFC PATCH 01/12] configure: Add iovisor/ubpf project
> >>> as a submodule for QEMU
> >>>
> >>> On Fri, Jun 17, 2022 at 03:36:19PM +0800, Zhang Chen wrote:
> >>>> Make iovisor/ubpf project be a git submodule for QEMU.
> >>>> It will auto clone ubpf project when configure QEMU.
> >>>
> >>> I don't think we need todo this. As it is brand new functionality we
> >>> don't have any back compat issues. We should just expect the distros
> >>> to ship ubpf if they want their QEMU builds to take advantage of it.
> >>>
> >>
> >> Yes, agree. It's the best way to use the uBPF project.
> >> But current status is distros(ubuntu, RHEL...) does not ship the
> >> iovisor/ubpf like the iovisor/bcc. So I have to do it.
> >> Or do you have any better suggestions?
> >
> > If distros want to support the functionality, they can add packages
> > for it IMHO.
> 
> Yes, let's please avoid new submodules. Submodules can sometimes be a
> real PITA (e.g. if you forget to update before rsync'ing your code to a
> machine that has limited internet access), and if users install QEMU from
> sources, they can also install ubpf from sources, too.
> And if distros want to support this feature, they can package ubpf on their
> own, as Daniel said.

Hi Daniel and Thomas,

I don't know much the background history of QEMU submodules, but meson build
is a submodule for QEMU too. It means user can't install QEMU from sources
with limited internet access. 
And back to Daniel's comments,  Yes, the best way is distros add the ubpf packages,
But maybe it's too late to implement new features for us. We can introduce the submodule now and
auto change to the distros's lib when distros add it.  For example QEMU's submodule SLIRP do it in the same way.
It's already added by most distros and still as a QEMU submodule. It make user experience the latest technology
with no other dependencies. uBPF infrastructure have the ability to extend the capabilities without requiring
changing source code. If we not allow it, we have to re-implement all the eBPF assembler, disassembler,
interpreter, and JIT compiler like DPDK userspace eBPF support (DPDK can't use ubpf project by license issue).

Thanks
Chen


> 
>   Thomas