Re: [PATCH v2 00/14] meson: Deprecate 32-bit host support

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

+Xen maintainers


On Mon, 3 Feb 2025, Richard Henderson wrote:
> On 2/3/25 04:54, Paolo Bonzini wrote:
> > On 2/3/25 04:18, Richard Henderson wrote:
> > > v1: 20250128004254.33442-1-richard.henderson@xxxxxxxxxx
> > > 
> > > For v2, immediately disable 64-on-32 TCG.
> > > 
> > > I *suspect* that we should disable 64-on-32 for *all* accelerators.
> > > The idea that an i686 binary on an x86_64 host may be used to spawn
> > > an x86_64 guest via kvm is silly and a bit more than niche.
> > 
> > At least Xen used to be commonly used with 32-bit dom0, because it saved
> > memory and dom0 would map in guest buffers as needed.  I'm not sure how
> > common that is these days, perhaps Stefano knows.
> 
> As a data-point, debian does not ship libxen-dev for i686.
> We cannot build-test this configuration at all.
> 
> I can build-test Xen for armhf, and I guess it would use i386-softmmu; it's
> unclear whether x86_64-softmmu and aarch64-softmmu are relevant or useful for
> an armhf host, or as an armhf binary running on an aarch64 host.


On the Xen side, there are two different use cases: x86 32-bit and ARM
32-bit.  

For x86 32-bit, while it was a very important use case in the past, I
believe it is far less so now. I will let the x86 maintainers comment on
how important it is today. 

For ARM 32-bit, I do not think we ever had many deployments, as most are
64-bit. Even when there are deployments, they do not typically use QEMU,
as QEMU is less important for Xen on ARM compared to x86. Therefore, I
would not block your cleanup and deprecation because of that. I will let
the other ARM maintainers chime in.