Re: [XEN PATCH v7 00/51] xen: Build system improvements, now with out-of-tree build!

[Alex Bennée <alex.bennee@xxxxxxxxxx>]

Anthony PERARD <anthony.perard@xxxxxxxxxx> writes:

> On Thu, Nov 04, 2021 at 03:49:36PM +0000, Alex Bennée wrote:
>> 
>> Anthony PERARD <anthony.perard@xxxxxxxxxx> writes:
>> 
>> > Patch series available in this git branch:
>> > https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fxenbits.xen.org%2Fgit-http%2Fpeople%2Faperard%2Fxen-unstable.git&amp;data=04%7C01%7Canthony.perard%40citrix.com%7C85bb0d32a72542aa9f6108d99fad9607%7C335836de42ef43a2b145348c2ee9ca5b%7C0%7C0%7C637716390172120458%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=WWS4yPu9%2BJxBkBiM5SBrH7kDtHkUzMGuKSSdPcgEYII%3D&amp;reserved=0
>> > br.build-system-xen-v7
>> >
>> > v7:
>> >     Out-of-tree build!
>> >
>> >     This mean many more patches. Everything after patch 27 is new.
>> >
>> >     There's a few new patch before that, but otherwise are rework of
>> >     v6.
>> 
>> This is something I've been looking forward to but obviously my QEMU
>> focused mind meant I did it wrong. Generally I create a builds subdir in
>> my tree with subdirs for each build flavour. So with:
>> 
>>   /home/alex/lsrc/xen/xen.git/builds/native
>> 
>> And executing:
>> 
>>   ➜  ../../configure
>
> Thanks for testing, but the patch series only focus on a subset of the
> repository, that is the hypervisor "xen.git/xen/". The rest of xen.git
> isn't ready for out-of-tree build unfortunately. A lot more work is
> needed.
>
>> In "build: adding out-of-tree support to the xen build" you describe the
>> Linux kernel style which works well where the config can be done after
>> the fact but I wonder if the configure approach is better suited to
>> something that needs a bunch of checks running. Is the configure script
>> pure autoconf? This should work out of the box IIRC.
>
> "xen.git/xen/" does use a build system similar to Linux's, we use
> Linux's Kconfig for example.

Ahh makes more sense in that context ;-)

> For the rest of the repository, it is indeed autoconf for the
> configuration phase. So yes running ./configure would be mostly ok, but
> it doesn't take care of Makefiles at the moment and I found one bug in
> our autoconf macros. Beyond that, our Makefiles aren't ready.
>
> xen.git isn't a single build system, they are several (at least one
> foreach of xen/ stubdom/ tools/)

I wonder if there is any millage in thinking about splitting
repositories and having them as subrepos of the main xen.git?

I can imagine building the core hypervisor as a standalone project is
something that is done a lot at least by developers. In a hypothetical
rust-vmm enabled world for example would you only need the hypervisor
itself if you had an alternate userspace to launch things?

>
> Cheers,


-- 
Alex Bennée