[Qemu-devel] MIPS, io-thread, icount and wfi

[Edgar E. Iglesias]

Hi,

I'm running an io-thread enabled qemu-system-mipsel with icount.
When the guest (linux) goes to sleep through the wait insn (waiting
to be woken up by future timer interrupts), the thing deadlocks.

IIUC, this is because vm timers are driven by icount, but the CPU is
halted so icount makes no progress and time stands still.

I've locally disabled vcpu halting when icount is enabled, that
works around my problem but of course makes qemu consume 100% host cpu.

I don't know why I only see this problem with io-thread builds?
Could be related timing and luck.

Would be interesting to know if someone has any info on how this was
intended to work (if it was)? And if there are ideas for better
workarounds or fixes that don't disable vcpu halting entirely.

Cheers