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Re: [Xen-devel] [RFC PATCH v1 02/10] xen/arm: register mmio handler at runtime

Hi Julien,

On Thu, Mar 27, 2014 at 8:32 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> On 03/27/2014 05:40 AM, Vijay Kilari wrote:
>> On Wed, Mar 26, 2014 at 8:17 PM, Julien Grall <julien.grall@xxxxxxxxxx> 
>> wrote:
>>> On 03/26/2014 12:29 PM, Vijay Kilari wrote:
>>>> Hi Julien,
>>>> On Fri, Mar 21, 2014 at 10:53 PM, Julien Grall <julien.grall@xxxxxxxxxx> 
>>>> wrote:
>>>>> On 03/21/2014 05:17 PM, Ian Campbell wrote:
>>>>>> On Wed, 2014-03-19 at 19:47 +0530, vijay.kilari@xxxxxxxxx wrote:
>>>>>>> From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
>>>>>>> mmio handlers are registers at compile time
>>>>>>> for drivers like vuart and vgic.
>>>>>>> Make mmio handler registered at runtime by
>>>>>>> creating linked list of mmio handlers
>>>>>> I'm not convinced of the need for this, certainly the vgic side can just
>>>>>> demux into v2 or v3 as necessary.
>>>>> Demux the code just add an indirection. We could have a list of mmio
>>>>> handler per domain and rely on it to call the right handler. A bit like 
>>>>> x86.
>>>>  Until Andrii adds IOMMU  handling should keep this patch? and adopt
>>>> to it later?
>>> I'm not sure to understand. IHMO, it doesn't sound right to upstream a
>>> patch that we know it will be superseded in a couple of months. Why
>>> can't you rework your patch to have it in good shape now?
>>  I assume that Andii's patch will be required to make mmio handlers
>> per domain. If not let me know references in x86 that I can make it
>> per domain specific mmio handlers.
> I have already pointed out to the x86 code few mails before.
> You can look at xen/arch/x86/intercept.c.

   From the x86/hvm/intercept.c file, the mmio handling of x86 is
similar to existing arm mmio handling in arm/io.c file, where the
handlers are registered statically.

  I understand that only requirement is to make vgic as domain specific
similar to vuart. Is that what you expect. Can you please make it clear?

 IMO, the io handling in x86/hvm/intercept.c is not required for arm.

>> I was more inclined to go with this patch for now because it helps to
>> go ahead with GICv3 and anything beyond this can be managed separately.
>> Please let me know you opinion.
> As I said on the email you answered, I'm not in favor to allow a this
> patch that we know it will superseded in less than a couple of months.
> It won't take you longer time than addressing the current requests on
> this patch.
> In last resort, you can use the demux solution from Ian. I don't agree
> with it but it's better than upstreaming an half-feature for no valid
> reason.
> Regards,
> --
> Julien Grall

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