Re: [Xen-devel] [RFC PATCH v2 13/22] xen/arm: its: Add virtual ITS command support

[Vijay Kilari <vijay.kilari@xxxxxxxxx>]

On Tue, May 5, 2015 at 5:17 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> On 05/05/15 12:06, Vijay Kilari wrote:
>>    One MSI per domain is always consumed because each domain during
>> ITS initialization creates Virtual ITS and sends basic initialization
>> commands (MAPC)
>
> AFAICT, MAPC won't be translated to a physical command. So not interrupt
> completion is necessary.
>
> Couldn't we defer the interrupt completion allocation until a PCI device
> is passthrough or a command requiring physical command is sent?

yes, but MAPC is generally followed by SYNC command and INVALL command
is also received during guest driver init.

On option that I can think of is that avoid posting  to physical
queue/completion
interrupt allocation, untill first MAPD command arrives for that domain.

Regards
Vijay

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