From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@citrix.com>
Subject: Re: [RFC PATCH v2 13/22] xen/arm: its: Add virtual ITS
 command support
Date: Tue, 5 May 2015 13:08:36 +0100
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To: Vijay Kilari <vijay.kilari@gmail.com>, Julien Grall <julien.grall@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Prasun Kapoor <Prasun.Kapoor@caviumnetworks.com>, Vijaya Kumar K <vijaya.kumar@caviumnetworks.com>, Julien Grall <julien.grall@linaro.org>, Tim Deegan <tim@xen.org>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>, Stefano Stabellini <stefano.stabellini@citrix.com>, manish.jaggi@caviumnetworks.com
List-Id: xen-devel@lists.xenproject.org

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