Re: [PATCH] tcg/arm: Reduce vector alignment requirement for NEON

[Richard W.M. Jones]

On Mon, Sep 13, 2021 at 09:19:22AM -0700, Richard Henderson wrote:
> On 9/13/21 4:07 AM, Richard W.M. Jones wrote:
> >>[    0.000000] Linux version 5.14.0-60.fc36.armv7hl 
> >>(mockbuild@buildvm-a32-12.iad2.fedoraproject.org) (gcc (GCC) 11.2.1 
> >>20210728 (Red Hat 11.2.1-1), GNU ld version 2.37-9.fc36) #1 SMP Mon Aug 30 
> >>14:08:34 UTC 2021
> >>
> >>I thought about parameterizing this patch further, but I can't think of
> >>another ISA that would be affected.  (i686 clumsily changed its abi 20
> >>years ago to avoid faulting on vector spills; other isas so far have
> >>allowed vectors to be unaligned.)
> >
> >Is it possible this change could have caused a more serious
> >regression?
> 
> I don't think so...
> 
> >Now when I try to boot the Fedora kernel using TCG on
> >armv7hl I can't even get to the point where it detects virtio-scsi
> >devices.
> >
> >Full log is here (go down to the bottom and work backwards):
> >
> >   https://kojipkgs.fedoraproject.org//work/tasks/7337/75597337/build.log
> 
> I downloaded the 5.14.0-60 kernel from above, and I can reproduce
> the original error, and I see that it's fixed afterward.

Thanks for checking that.  I did spend much of today attempting to get
an armv7 guest installed on my RPi so I could reproduce this more
reliably, but eventually gave up because of a variety of other
problems (one apparently in qemu: https://bugzilla.redhat.com/1633328)

> I'll have a look at this new build log in a moment...
> 
> 
> r~

Rich.

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