Re: [PATCH v2 0/6] Deprecate support for 32-bit x86 and arm hosts

[Peter Maydell <peter.maydell@xxxxxxxxxx>]

On Fri, 3 Mar 2023 at 11:09, John Paul Adrian Glaubitz
<glaubitz@xxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello!
>
> On Fri, 2023-03-03 at 10:48 +0100, Thomas Huth wrote:
> > x86 ==> deprecate both, user and system emulation support on
> >          32-bit hosts
> > arm ==> deprecate only system emulation on 32-bit hosts.
>
> I would recommend against dropping support for 32-bit hosts for qemu-user
> as there are some cases where the emulation of 32-bit user code on 64-bit
> hosts does not work properly [1].
>
> Adrian
>
> > [1] https://sourceware.org/bugzilla/show_bug.cgi?id=23960

I failed entirely to get any traction with persuading the
kernel folks to provide an API to let QEMU work in that
"32-bit guest wants a 32-bit dirent but the kernel is
providing a 64-bit hash value as a dirent" case. Somebody kindly
wrote some kernel patches but they went absolutely nowhere.

It seems to only happen for certain kinds of 32-bit guest, where
the guest libc is not also using 64-bit dirents. So at least as
far as Arm guests are concerned the effective result was "the
older arm binaries that were built to need a 32-bit dirent are
just not around any more, so very few people run into the problem".
You can also work around it by using a different host filesystem
type, I think.

thanks
-- PMM