From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@linaro.org>
Subject: Re: [PATCH v3 20/24] xen/passthrough: Extend
 XEN_DOMCTL_assign_device to support DT device
Date: Fri, 13 Mar 2015 16:47:13 +0000
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To: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>, tim@xen.org, Ian Jackson <ian.jackson@eu.citrix.com>, stefano.stabellini@citrix.com, Jan Beulich <jbeulich@suse.com>, xen-devel@lists.xenproject.org, Daniel De Graaf <dgdegra@tycho.nsa.gov>
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Hi,

On 11/03/2015 13:50, Julien Grall wrote:
> On 11/03/2015 12:37, Ian Campbell wrote:
>> On Tue, 2015-03-10 at 16:33 +0000, Julien Grall wrote:
>>> Hi Ian,
>>>
>>> On 20/02/15 17:17, Ian Campbell wrote:
>>>>> +    /* TODO: Do we need to check is_dying? Mostly to protect against
>>>>> +     * hypercall trying to passthrough a device while we are
>>>>> +     * dying.
>>>>
>>>> FWIW the PCI case appears not to care...
>>>
>>> There is one place in XEN_DOMCTL_assign_device...
>>>
>>> Although I don't understand much the usage of is_dying.
>>>
>>>>> +     */
>>>>> +
>>>>> +    switch ( domctl->cmd )
>>>>> +    {
>>>>> +    case XEN_DOMCTL_assign_device:
>>>>> +        ret = -ENOSYS;
>>>>> +        if ( domctl->u.assign_device.dev != XEN_DOMCTL_DEV_DT )
>>>>> +            break;
>>>>
>>>> You added something similar to iommu_do_pci_domctl, would it not be
>>>> preferable for the caller to switch on domctl->u.assign_device.dev and
>>>> call the correct iommu_do_*_domctl?
>>>
>>> I though about it. It would require to stub iommu_do_*_domctl. So I
>>> preferred to chose the current solution.
>>
>> You mean iommu_do_{pci,dt}_domctl?
>>
>> IIRC you already added suitable #defines for when these features are
>> present, so reusing them at the call sites wouldn't be too bad, or else
>> stubs aren't the worst thing either.
>
> Hmmm I think I got you point now. Do you mean have something like:
>
> switch (domctl->u.assign_device.dev)
> {
> #ifdef HAS_PCI
> case XEN_DOMCTL_DEV_PCI:
>      ret = iommu_do_pci_domctl();
>      break;
> #endif
> #ifdef HAS_DEVICE_TREE
> case XEN_DOMCTL_DEV_DT:
>      ret = iommu_do_dt_domctl()
>      break;
> #endif
>
> default:
>     ret = -ENOSYS;
> }

I though more about it and it won't be possible to do it unless we 
decode DOMCTL too.

This is because the DOMCTL_get_device_group use a different structure 
and is only for PCI.

So unless we decide to consolidate the 2 DOMCTL structures in a single 
one. I would prefer to keep the current solution with the suggestion 
made by Jan earlier.

Regards,

-- 
Julien Grall