Re: [PATCH] interrupt preemption support

Avi Kivity
2007-03-19T14:03:19Z

Avi Kivity wrote:
> Gregory Haskins wrote:
>> Hi Avi,
>> You make good points. I will convert to a nest lock design and
>> resubmit. Should I use two mutexes, or a mutex and spinlock?
>>
>> Also, do you have any suggestions on the signum I should use to IPI
>> the running guest? Should I use one of the normal signals (SIGUSR)
>> or should I start a block of defined signals in the RT range (>32)?
>>
>
> For a short term solution, where the apic is in userspace, we can just
> say ipi == signal, and not require any locking. Qemu will catch the
> signal and call the appropriate apic function. The signal number
> should be set from userspace.
>

Note that as long as the apic code is in userspace, the sending side is
also in userspace, so all the IPI related stuff doesn't touch the kernel.

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