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

[Julien Grall <julien.grall@citrix.com>]

On 05/05/15 13:00, Vijay Kilari wrote:
> On Tue, May 5, 2015 at 5:17 PM, Julien Grall <julien.grall@citrix.com> 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.

You could ignore SYNC, INVALL until a PCI device is passthrough to the
guest.

> 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.

I prefer the solution where we ignore any command until a PCI device is
passthrough. It's more logical.

Regards,

-- 
Julien Grall