Update QEMU to 7.0.0

[alexcrichton]

Seems good for us to stay updated as we're relying on it for tests, so
this updates the version of QEMU used on CI to run cross-compiled tests
for s390x and AArch64

[cfallin]

cc @uweigand for s390x issues (qemu is segfaulting) -- are there any known problems in qemu 7.0.0 wrt s390x support?

[alexcrichton]

Alas perhaps an update another day!

[uweigand]

cc @uweigand for s390x issues (qemu is segfaulting) -- are there any known problems in qemu 7.0.0 wrt s390x support?

I don't know of any known problems, but some regression may of course have crept in. I'll try to reproduce a run with qemu 7.0.0 locally.

[uweigand]

It seems this patch: https://lists.gnu.org/archive/html/qemu-devel/2021-09/msg07466.html is causing the problem. This changes the layout of a data structure on the signal stack that user-space code relies upon. Reverting the data structure change using the attached patch makes the problem go away for me.
qemu-fix-s390-sigframe.txt

[alexcrichton]

Oh nice! I don't know of any pressing need to land this so I think it's ok to wait for this to be resolved upstream in a release before we update.

[uweigand]

Oh nice! I don't know of any pressing need to land this so I think it's ok to wait for this to be resolved upstream in a release before we update.

Just FYI the patch to fix this regression has now been merged; QEMU 7.1.0 should have the fix.

[iii-i]

I brought ci/qemu-madvise.patch upstream: https://lists.gnu.org/archive/html/qemu-devel/2022-06/msg03752.html.
You should be able to drop it once you switch to 7.1.0.

[alexcrichton]

Oh awesome, thanks @iii-i!