Re: [kvm-unit-tests PATCH] lib/devicetree: Support 64 bit addresses for the initrd

Marc Zyngier
2022-02-15T09:26:21Z

On Tue, 15 Feb 2022 07:32:12 +0000,
Andrew Jones <drjones@redhat.com> wrote:
>
> On Mon, Feb 14, 2022 at 05:01:40PM +0000, Marc Zyngier wrote:
> > Hi all,
> >
> > On Mon, 14 Feb 2022 16:20:13 +0000,
> > Alexandru Elisei <alexandru.elisei@arm.com> wrote:
> > >
> > > Hi Drew,
> > >
> > > (CC'ing Marc, he know more about 32 bit guest support than me)
> > >
> > > On Mon, Feb 14, 2022 at 03:24:44PM +0100, Andrew Jones wrote:
> > > > I'm not sure it's worth adding another patch on top for that now, though.
> > > > By the lack of new 32-bit arm unit tests getting submitted, I'm not even
> > > > sure it's worth maintaining 32-bit arm at all...
> > >
> > > As far as I know, 32 bit guests are still very much supported and
> > > maintained for KVM, so I think it would still be very useful to have the
> > > tests.
> >
> > I can't force people to write additional tests (or even start writing
> > the first one), but I'd like to reaffirm that AArch32 support still is
> > a first class citizen when it comes to KVM/arm64.
> >
> > It has been tremendously useful even in the very recent past to debug
> > issues that were plaguing bare metal Linux, and i don't plan to get
> > rid of it anytime soon (TBH, it is too small to even be noticeable).
> >
>
> OK, let's keep 32-bit arm support in kvm-unit-tests, at least as long as
> we can find hardware to test it with (I still have access to a mustang).

That HW will be with us for a *very* long time, given how popular
things like A53 and A72 have been (and still are).

> Does kvmtool support launching AArch32 guests? If so, then I suppose we
> should also test kvmtool + 32-bit arm kvm-unit-tests.

It does. Passing --aarch32 as a parameter results in AArch32 EL1 being
selected. The only thing that doesn't work with kvmtool and this flag
is the kvmtool-provided init when booting a 32bit kernel directly (we
only carry a 64bit version). This should not affect unit tests, which
are standalone.

Thanks,

M.

--
Without deviation from the norm, progress is not possible.