[PATCH 08/26] KVM: PPC: Add PV guest critical sections

[Avi Kivity]

On 06/26/2010 02:24 AM, Alexander Graf wrote:
> When running in hooked code we need a way to disable interrupts without
> clobbering any interrupts or exiting out to the hypervisor.
>
> To achieve this, we have an additional critical field in the shared page. If
> that field is equal to the r1 register of the guest, it tells the hypervisor
> that we're in such a critical section and thus may not receive any interrupts.
>    

Is r1 reserved for this purpose?  Can't it match accidentally?

Why won't zero/nonzero work for this?

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error compiling committee.c: too many arguments to function