Re: [Qemu-devel] [PATCH] kvm: Move kvm_allows_irq0_override() to target-i386

[Avi Kivity <avi@redhat.com>]

On 07/23/2012 04:55 PM, Cornelia Huck wrote:
>> > Basically, we have some flags in our control block we can set so that
>> > the cpu drops out of SIE whenever external/I/O/... interrupts are
>> > enabled and then have the host do the lowcore updates, psw swaps, etc.
>> 
>> Can you write them from a different cpu and expect them to take effect?
>> 
>> How do you emulate an interrupt with a large guest?  You have to update
>> the flags in the control blocks for all vcpus; then restore them when
>> the interrupt is delivered?
> 
> We may access the flags for any vcpu via the kvm_s390_float_interrupt
> structure which is contained in kvm->arch.
> 
> We'll get control when a vcpu enters a wait state and try to deliver
> pending interrupts or set/clear the flags. Moreover, idle vcpus are on
> a wait queue and are the first target for getting an interrupt injected.

Okay.  And you can ask a vcpu to exit when it enables interrupts,
without interrupting it?

On x86, we have to IPI the vcpu so it drops to the host, ask it to let
us know when interrupts are enabled, and let it run again.

-- 
error compiling committee.c: too many arguments to function