Re: [PATCH v2] xen/passthrough: Support a single iommu_domain per xen domain per SMMU

[Manish Jaggi <mjaggi@caviumnetworks.com>]

On Tuesday 24 March 2015 07:34 PM, Robert VanVossen wrote:
>
> On 3/24/2015 7:07 AM, Manish Jaggi wrote:
>> On Monday 23 March 2015 07:16 PM, Robbie VanVossen wrote:
>>> If multiple devices are being passed through to the same domain and they
>>> share a single SMMU, then they only require a single iommu_domain.
>>>
>>> In arm_smmu_assign_dev, before a new iommu_domain is created, the
>>> xen_domain->contexts is checked for any iommu_domains that are already
>>> assigned to device that uses the same SMMU as the current device. If one
>>> is found, attach the device to that iommu_domain. If a new one isn't
>>> found, create a new iommu_domain just like before.
>>>
>>> The arm_smmu_deassign_dev function assumes that there is a single
>>> device per iommu_domain. This meant that when the first device was
>>> deassigned, the iommu_domain was freed and when another device was
>>> deassigned a crash occured in xen.
>>>
>>> To fix this, a reference counter was added to the iommu_domain struct.
>>> When an arm_smmu_xen_device references an iommu_domain, the
>>> iommu_domains ref is incremented. When that reference is removed, the
>>> iommu_domains ref is decremented. The iommu_domain will only be freed
>>> when the ref is 0.
>>>
>>> Signed-off-by: Robbie VanVossen <robert.vanvossen@dornerworks.com>
>> Hi,
>> Are you adding a PCI passthrough support to Xen ?. I am in process of
>> sending smmu driver patches based on juliens latest code.
>>
> Nope, I am just working on what this patch describes
Your patch is doing similar thing what am working on. As per the Xen 4.6 
release I took smmu for pci-passthorugh. I didnt send smmu patches so 
far as there are other dependency patches I need to send first like 
pci_host_bridge register hypercall patch.

Julien/Ian could you please hold the merge of this patch.
> Thanks,
> Robbie VanVossen
> DornerWorks
>