Re: gdb support for SME-without-SVE ?

Peter Maydell via Gdb
2026-01-30T18:59:48Z

On Fri, 30 Jan 2026 at 18:40, Thiago Jung Bauermann
<thiago.bauermann@linaro.org> wrote:
>
> Peter Maydell <peter.maydell@linaro.org> writes:
>
> > On Fri, 30 Jan 2026 at 18:18, Thiago Jung Bauermann
> > <thiago.bauermann@linaro.org> wrote:
> >> Peter Maydell <peter.maydell@linaro.org> writes:
> >> > With my updated QEMU
> >> > (which you can find in the new "sme-no-sve-2" in my gitlab repo)
> >> > that can now run the tests without making the kernel fall over.
> >> > It reports:
> >> >
> >> > # of expected passes 241
> >> > # of unexpected failures 37
> >> >
> >> > Is that the same as you see on the fast model, or does this
> >> > indicate that I still have more QEMU bugs to track down?
> >> > (Peeking into gdb.log, these failures seem to be run-on
> >> > failures from the program under test getting a SIGILL
> >> > in initialize_zt_state(), so my guess is QEMU is still not
> >> > quite right.)
> >>
> >> Indeed, there seems to be something off with QEMU.
> >> On FVP, all the tests pass:
> >>
> >> === gdb Summary ===
> >>
> >> # of expected passes 278
> >
> > Just to check, does your FVP have the SME2p1 feature ?
> > (Should show up as "sme2p1" in the feature list in /proc/cpuinfo
> > in the guest.)
>
> It doesn't. Here's my FVP's feature list:
>
> Features : fp asimd evtstrm crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop asimddp asimdfhm dit uscat ilrcpc flagm sb paca pacg gcs dcpodp flagm2 frint i8mm bf16 dgh rng bti ecv afp sme smei16i64 smef64f64 smei8i32 smef16f32 smeb16f32 smef32f32 wfxt ebf16 cssc mops hbc poe lsfe

OK. If I nobble QEMU locally to not enable SME2/SME2p1 (which
needs source changes, as there's no command line flag for it)
then I get a complete set of passes:

# of expected passes 278

So possibilities:
* bug in your test code for the SME2p1 case
* bug in the kernel's support for SME2p1
* bug in QEMU's support for SME2p1

-- PMM