Re: [PATCH v3 01/10] iommu: Introduce Shared Virtual Addressing API

[Jean-Philippe Brucker <jean-philippe.brucker@arm.com>]

On 23/09/2018 03:39, Lu Baolu wrote:
>> +int iommu_sva_init_device(struct device *dev, unsigned long features,
>> +                    unsigned int min_pasid, unsigned int max_pasid)
>> +{
>> +     int ret;
>> +     struct iommu_sva_param *param;
>> +     struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> 
> This doesn't work for vt-d. The domains for host iova are self-managed
> by vt-d driver itself. Hence, iommu_get_domain_for_dev() will always
> return NULL unless an UNMANAGED domain is attached to the device.
> 
> How about
> 
>        const struct iommu_ops *ops = dev->bus->iommu_ops;>
> instead?

Right, this should work. I also needed to change the IOMMU ops
introduced in patch 3 to not take a domain. It's a shame that iommu-sva
can't get the device's current domain, I was hoping we could manage the
bonds per domain in common code. But it's not a big deal and on the
upside, it simplifies these core patches.

I was previously relying on "if we have a domain, then
iommu_group_add_device has been called and therefore dev->iommu_param is
set". I now do the same as iommu_register_device_fault_handler, check if
iommu_param isn't NULL. I don't think there is a race with
iommu_group_add/remove_device, since the device driver cannot call SVA
functions before the core called its probe() callback and after the core
called its remove() callback, which happen after
iommu_group_add_device() and before iommu_group_remove_device()
respectively. Though I don't have a full picture here, and might be wrong.

I pushed the updated version to my sva/current branch

Thanks,
Jean