Re: intermittent hang in qos-test for qemu-system-i386 on 32-bit arm host

[Richard Henderson]

On 7/11/21 5:16 AM, Peter Maydell wrote:
> On Sun, 11 Jul 2021 at 13:10, Coiby Xu <coiby.xu@gmail.com> wrote:
> > Hi Peter,
> >
> > On Sat, Jul 10, 2021 at 02:30:36PM +0100, Peter Maydell wrote:
> > > I've noticed recently that intermittently 'make check' will hang on
> > > my aarch32 test system (really an aarch64 box with an aarch32 chroot).
> >
> > I have a newbie question. How do you do an aarch32 chroot on an aarch64
> > box? At least, this issue seems to be not reproducible on an aarch64 box
> > directly. I specifically ran the qos-test for 5 consecutive times and
> > each time the test could finish successfully,
>
> Your aarch64 host CPU needs to support aarch32 at EL0 (some
> AArch64 CPUs are pure-64 bit these days). The host kernel needs
> to implement the 32-bit compat layer. It probably also needs to be
> built for 4K pages (which mostly means "not RedHat"). Then you can
> set up the 32-bit chroot however you'd normally set up a chroot
> (for Debian you can do this with debootstrap; other distros will vary;
> schroot is also a bit nicer than raw chroot IMHO.)

If you do have a kernel built with 64k pages ("RedHat"), but you do have a host cpu that 
supports aarch32 at EL1 and EL0, then you can run aarch32 under KVM.

The command-line I use is

../run/bin/qemu-system-aarch64 -m 4096 -smp 8 -nographic \
  -M virt -cpu host,aarch64=off --accel kvm \
  -kernel vmlinuz-4.19.0-16-armmp-lpae \
  -initrd initrd.img-4.19.0-16-armmp-lpae \
  -append 'console=ttyAMA0 root=/dev/vda2' \
  -drive if=none,file=hda.q,format=qcow2,id=hd,discard=on \
  -device virtio-blk-device,drive=hd \
  -netdev tap,id=tap0,br=virbr0,helper=/usr/libexec/qemu-bridge-helper \
  -device virtio-net-device,netdev=tap0

I believe that I had to perform the install under tcg because I couldn't find the right 
magic to boot off the debian cdrom with kvm.


r~