Re: [PATCH] arm64: KVM: export current vcpu->pause state via pseudo regs

From: Peter Maydell
Date: Thu Jul 31 2014 - 13:37:00 EST

On 31 July 2014 18:21, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> What does ARM do if you have a WFI while interrupts are disabled? On
> x86 after "cli;hlt" only an NMI will wake you up. With spurious
> wakeups, it's pretty much guaranteed that you will break such "cli;hlt"
> sequences.

The architecture mandates some things that *must* wake you from
a WFI, but it also allows wakeups for other reasons not listed, or
for no reason at all. It's perfectly valid to implement WFI as a NOP
(though it would not be very good for power efficiency, obviously).
Guests which don't surround WFI with a "check whether we should
just go back to WFI" loop are buggy.

-- PMM
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