Re: [PATCH v13 07/13] iommu/vt-d: Add SVA domain support

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2022/9/22 23:49, Jason Gunthorpe wrote:
> On Tue, Sep 06, 2022 at 08:44:52PM +0800, Lu Baolu wrote:
>> +static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid)
>> +{
>> +	struct intel_iommu *iommu = device_to_iommu(dev, NULL, NULL);
>> +	struct iommu_domain *domain;
>> +
>> +	/* Domain type specific cleanup: */
>> +	domain = iommu_get_domain_for_dev_pasid(dev, pasid, 0);
>> +	if (domain) {
>> +		switch (domain->type) {
>> +		case IOMMU_DOMAIN_SVA:
>> +			intel_svm_remove_dev_pasid(dev, pasid);
>> +			break;
>> +		default:
>> +			/* should never reach here */
>> +			WARN_ON(1);
>> +			break;
> 
> This is eventually going to need a lot more cleaning up to split out
> the PASID from the SVM stuff.
> 
> SVA should *only* be a set of predefined handlers (in the core code!)
> for the generic PRI mechanism, it shouldn't be entangled deeply into
> PASID or the drivers like this.
> 
> When we get done with this, the flow should have the core code attach
> a SVA domain to a PASID with PRI enabled and the core code should
> supply a generic PRI implementation that does the mmu_notifier
> stuff.

Yes. Agreed.

At the beginning of this project, I wanted to consolidate the mm
notifications into the core. However, ARM SMMUv3 and Intel handle the mm
notifications a little differently. Then I decided to do this work
separately from the current series.

> 
> Also, stuff like this:
> 
> 				/* We mandate that no page faults may be outstanding
> 				 * for the PASID when intel_svm_unbind_mm() is called.
> 				 * If that is not obeyed, subtle errors will happen.
> 				 * Let's make them less subtle... */
> 
> Are going to be problematic for VFIO as well. In a VFIO world the
> entire RID and its entire PASID table has to be owned by VFIO and
> never shared - so these sequencing issues should be solvable.
> 
> But this is all for further series..

Yes. All these sound interesting future series.

> 
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

I'm very appreciated for your time.

Best regards,
baolu