> From: Lu Baolu <baolu...@linux.intel.com>
> Sent: Tuesday, June 21, 2022 10:44 PM
>
> The sva iommu_domain represents a hardware pagetable that the IOMMU
> hardware could use for SVA translation. This adds some infrastructure
> to support SVA domain in the iommu common layer. It includes:
>
> - Extend the iommu_domain to support a new IOMMU_DOMAIN_SVA
> domain
> type. The IOMMU drivers that support SVA should provide the sva
> domain specific iommu_domain_ops.
> - Add a helper to allocate an SVA domain. The iommu_domain_free()
> is still used to free an SVA domain.
> - Add helpers to attach an SVA domain to a device and the reverse
> operation.
>
> Some buses, like PCI, route packets without considering the PASID value.
> Thus a DMA target address with PASID might be treated as P2P if the
> address falls into the MMIO BAR of other devices in the group. To make
> things simple, the attach/detach interfaces only apply to devices
> belonging to the singleton groups, and the singleton is immutable in
> fabric i.e. not affected by hotplug.
>
> The iommu_attach/detach_device_pasid() can be used for other purposes,
> such as kernel DMA with pasid, mediation device, etc.
I'd split this into two patches. One for adding iommu_attach/
detach_device_pasid() and set/block_dev_pasid ops, and the
other for adding SVA.
> struct iommu_domain {
> unsigned type;
> const struct iommu_domain_ops *ops;
> unsigned long pgsize_bitmap; /* Bitmap of page sizes in use */
> - iommu_fault_handler_t handler;
> - void *handler_token;
> struct iommu_domain_geometry geometry;
> struct iommu_dma_cookie *iova_cookie;
> + union {
> + struct { /* IOMMU_DOMAIN_DMA */
> + iommu_fault_handler_t handler;
> + void *handler_token;
> + };
why is it DMA domain specific? What about unmanaged
domain? Unrecoverable fault can happen on any type
including SVA. Hence I think above should be domain type
agnostic.
> + struct { /* IOMMU_DOMAIN_SVA */
> + struct mm_struct *mm;
> + };
> + };
> };
>
> +
> +struct iommu_domain *iommu_sva_domain_alloc(struct device *dev,
> + struct mm_struct *mm)
> +{
> + const struct iommu_ops *ops = dev_iommu_ops(dev);
> + struct iommu_domain *domain;
> +
> + domain = ops->domain_alloc(IOMMU_DOMAIN_SVA);
> + if (!domain)
> + return NULL;
> +
> + domain->type = IOMMU_DOMAIN_SVA;
It's a bit weird that the type has been specified when calling
ops->domain_alloc while it still leaves to the caller to set the
type. But this is not caused by this series. could be cleaned
up separately.
> +
> + mutex_lock(&group->mutex);
> + curr = xa_cmpxchg(&group->pasid_array, pasid, NULL, domain,
> GFP_KERNEL);
> + if (curr)
> + goto out_unlock;
Need check xa_is_err(old).
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