Mark Cave-Ayland <mark.cave-ayland@xxxxxxxxxxxx> writes: > On 19/02/2019 04:20, Michael Ellerman wrote: >> Mark Cave-Ayland <mark.cave-ayland@xxxxxxxxxxxx> writes: >>>>> unexpectedly removed the MSR_FE0 and MSR_FE1 bits from the bitmask used to >>>>> update the MSR of the previous thread in __giveup_fpu() causing a KVM-PR MacOS >>>>> guest to lockup and panic the kernel. >> >> Which kernel is panicking? The guest or the host? > > It's the host kernel. As long as you occasionally tap a few keys to keep the screen > blanking disabled then you can see the panic on the physical console. Ah crap I assumed you meant the guest kernel. > I've uploaded a photo I took during the bisection containing the panic when booting > MacOS X 10.2 under qemu-system-ppc to > https://www.ilande.co.uk/tmp/qemu/macmini-kvm.jpg in case you find it useful. OK. That's a host crash, but only because init died (systemd). Though the reason it died is because we didn't clear FE0/1 properly, so still a kernel bug. > Given that it's really easy to recreate, let me know if you want me to do a git > pull/rebuild and/or if you need any debugging information as it's easy for me to > reproduce. I think that's OK. It's reasonably clear what's going on. >>> 2) Is this the right fix? I'm told that MacOS guests already run without this patch >>> on a G5 under 64-bit KVM-PR which may suggest that this is a workaround for another >>> bug elsewhere in the 32-bit powerpc code. >> >> That's slightly worrying. It's hard to say without more detail on why >> the guest is crashing. >> >> I think your patch looks OK based just on the fact that it restores the >> previous behaviour, so I'll pick it up and pass it through my usual >> testing. If nothing breaks I'll merge it. > > That would be great! Does it need a CC to stable too? It would be great if this would > get picked up in the next set of Debian ports kernels, for example. I'll add Cc stable. cheers
