Re: [Xen-devel] [PATCH v3 13/13] xen/iommu: smmu: Advertise when the SMMU support coherent table walk

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 20/02/15 14:13, Ian Campbell wrote:
> On Fri, 2015-02-20 at 14:07 +0000, Julien Grall wrote:
>> On 20/02/15 13:34, Ian Campbell wrote:
>>> On Fri, 2015-01-30 at 18:49 +0000, Julien Grall wrote:
>>>> @@ -2896,6 +2911,16 @@ static __init int arm_smmu_dt_init(struct 
>>>> dt_device_node *dev,
>>>>    if ( !rc )
>>>>            iommu_set_ops(&arm_smmu_iommu_ops);
>>>>  
>>>> +  /*
>>>> +   * The last added SMMU is the first element of arm_smmu_devices.
>>>> +   * It's not necessary to take the lock because only the boot CPU is
>>>> +   * initialized the SMMU devices.
>>>
>>> Why is only the last added SMMU of interest? Do we not need to take the
>>> union and/or intersection of them all?
>>
>> It's already the case. The function arm_smmu_dt_init is called on every
>> SMMU. So the last added SMMU is the one we are currently added.
> 
> Why do we not just have it in our hand and have to go scrobbling round
> in a list then?

[..]

> Rather than making assumptions about the list ordering and if we can't
> just get hold of the smmu pointer directly from arm_smmu_dt_init then
> I'd prefer an explicit walk of the list at some appropriate point after
> everything has been registered up.

Because that would require to modify more heavily arm_smmu_dt_init.

Given that we control the way we add the SMMU in the list, the explicit
walk sounds pointless.

Regards,

-- 
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel