Re: [Qemu-devel] [RFC] create a single workqueue for each vm to update vm irq routing table

Paolo Bonzini
2013-11-26T15:59:06Z

Il 26/11/2013 16:35, Avi Kivity ha scritto:
>>>> If we want to ensure, we need to use a different mechanism for
>>>> synchronization than the global RCU. QRCU would work; readers are not
>>>> wait-free but only if there is a concurrent synchronize_qrcu, which
>>>> should be rare.
>>> An alternative path is to convince ourselves that the hardware does not
>>> provide the guarantees that the current code provides, and so we can
>>> relax them.
>> No, I think it's a reasonable guarantee to provide.
>
> Why?

Because IIUC the semantics may depend not just on the interrupt
controller, but also on the specific PCI device. It seems safer to
assume that at least one device/driver pair wants this to work.

(BTW, PCI memory writes are posted, but configuration writes are not).

Paolo