Re: [PATCH v3 08/13] xen/passthrough: iommu: Basic support of device tree assignment

[Julien Grall <julien.grall@linaro.org>]

Hi Ian,

On 19/03/14 10:12, Ian Campbell wrote:
>> On 03/18/2014 04:33 PM, Ian Campbell wrote:
>>> On Tue, 2014-03-11 at 15:49 +0000, Julien Grall wrote:
>>>> Add IOMMU helpers to support device tree assignment/deassignment. This patch
>>>> introduces 2 new fields in the dt_device_node:
>>>>      - is_protected: Does the device is protected by an IOMMU
>>>>      - next_assigned: Pointer to the next device assigned to the same
>>>>      domain
>>>
>>> Am I correct that this list is not maintained for dom0? The behaviour of
>>> dt_assign_device and dt_deassign_device seems to rely on it?
>>
>> DOM0 will call dt_assign_device for every device protected by the IOMMU
>> (see patch #9). So it will itself have a list maintained.
>
> Does this not mean that iommu_assign_dt_device will refuse to assign the
> device to another domain (next_assigned list is not empty).

Yes. After thinking, I'm not sure we want maintain a list for dom0.
At least the iommu_deassign_dt_device function is wrong because the 
device is not reassigned to dom0 (from the list point of view).


> BTW, next_assigned is not a very good name for this list, since the
> "nextness" is abstracted away. Consider just device_list.

I found device_list too generic. We don't know if it's the list of all 
the devices or just the ones of a specific domain.

What about domain_device_list?

Regards,

-- 
Julien Grall