Re: [RFC 11/19] xen/passthrough: Call arch_iommu_domain_destroy before calling iommu_teardown

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

On 06/17/2014 02:04 PM, Jan Beulich wrote:
>>>> On 17.06.14 at 14:38, <julien.grall@linaro.org> wrote:
>> On 06/17/2014 10:29 AM, Jan Beulich wrote:
>>>>>> On 17.06.14 at 11:18, <julien.grall@linaro.org> wrote:
>>>> On 17/06/14 09:07, Jan Beulich wrote:
>>>>>>>> On 16.06.14 at 18:17, <julien.grall@linaro.org> wrote:
>>>>>> --- a/xen/drivers/passthrough/iommu.c
>>>>>> +++ b/xen/drivers/passthrough/iommu.c
>>>>>> @@ -219,10 +219,10 @@ void iommu_domain_destroy(struct domain *d)
>>>>>>       if ( !iommu_enabled || !hd->platform_ops )
>>>>>>           return;
>>>>>>
>>>>>> +    arch_iommu_domain_destroy(d);
>>>>>> +
>>>>>>       if ( need_iommu(d) )
>>>>>>           iommu_teardown(d);
>>>>>> -
>>>>>> -    arch_iommu_domain_destroy(d);
>>>>>
>>>>> At the first glance this doesn't look right, including the explanation
>>>>> you gave (why would devices still be assigned to a guest at this
>>>>> point).
>>>>
>>>> Because the toolstack may forget to deassign a device. How do you handle 
>>>> this case in x86? In the SMMU case, this will mean a memory leak and 
>>>> misconfiguration of the registers.
>>>
>>> Proper tool stack behavior is required (and not just here).
>>
>> I think this is important to handle toolstack failure (such as crash)
>> just in case. Hence it doesn't add much code for this purpose.
> 
> If you think this is necessary, then there's no reason to make this
> ARM-specific (which in turn would eliminate the need for this to sit
> in an arch hook).

We will have to do DT/PCI specific as I don't use the same way to know
which device is assigned to which guest.

I won't be able to write (or at least test) the piece of code for the
PCI part as my ARM board doesn't support PCI and I don't have a Xen
setup for x86.

Regards,

-- 
Julien Grall