Re: [Xen-devel] xen interrupt

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

Please do not top post.

On Mon, 2013-03-18 at 12:05 +0000, åä wrote:


>  In your reply, you said that there is no concept of multiple VMs
> being registered to receive a single interrupt. For disk interrupt or
> network interrupt, every virtual machine needs to read or write data
> from or to disk or network card. I can not understand why there is no
> concept of multiple VMs being registered to receive a single
> interrupt.

Only one guest sees the physical disk (typically dom0) and therefore
receives the physical interrupt for that disk.

Guests see a PV disk device, and there is one of those per virtual disk,
each with its own event channel tied to the appropriate guest.

The PV devices communicate with a PV backend in the domain which
contains the physical disk and it takes care of the underlying I/O.

So each domain has its own disk evtchn and the backend domain has an
evtchn corresponding to the physical disk controllers interrupt.

Ian.


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