Re: [Qemu-devel] SEV and WFE instructions on ARM

[Peter Maydell]

On 26 November 2013 12:51, Walsh, Benjamin <address@hidden> wrote:
> I was looking at using WFE on QEMU, found that it is
> implemented as a NOP, googled and I found this thread.
>
> I am not using this for SMP, simply to implement sleep, so the busy
> loop is conceptually OK. Except, of course, that QEMU floors the
> host CPU at 100% in the idle loop.

FWIW, Linux uses WFI for its idle loop:
http://lxr.linux.no/#linux+v3.12.1/arch/arm/mm/proc-v7.S#L64

If you're in a position to recode your idle loop to WFI
instead of WFE that would be a workaround, because
QEMU does halt the guest cpu on WFI, so we won't
burn host CPU in a WFI-based idle loop.

-- PMM