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Re: [Xen-devel] [PATCH v2 19/21] xen/arm: Reserve region in guest memory for device passthrough

On 08/06/2014 05:44 PM, Stefano Stabellini wrote:
> On Wed, 6 Aug 2014, Julien Grall wrote:
>> Hi Stefano,
>> On 08/06/2014 05:27 PM, Stefano Stabellini wrote:
>>> On Thu, 31 Jul 2014, Julien Grall wrote:
>>>> This region will be split by the toolstack to allocate MMIO range for eac
>>>> device.
>>>> For now only reserve a 768MB region, this should be enought to passthrough
>>>> multiple device at the same time.
>>>> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
>>>> ---
>>>> I can't allocate easily a range of 1GB in the current layout without shrink
>>>> the first RAM bank. So I decided to use only 768MB. If in the future we 
>>>> need
>>>> more, then we will have to choose at runtime the guest layout.
>>>>     Changes in v2:
>>>>         - Bump the reserved region from 512MB to 768MB
>>> Better than nothing.
>>> Would it be possible to add a second region > 4GB? Maybe after RAM?
>>> How hard would be to handle that?
>> It won't work if the guest is using short-descriptor translation table
>> format because only 32 bits address will be supported.
> I know.

I don't plan to handle another region for this series. If someone come
with a real use case, then I will think about it.


Julien Grall

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