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SubjectRe: [PATCH v2 5/8] iommu/vt-d: Make device pasid attachment explicit
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On 3/28/23 7:21 AM, Jacob Pan wrote:
> diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
> index 65b15be72878..b6c26f25d1ba 100644
> --- a/drivers/iommu/intel/iommu.h
> +++ b/drivers/iommu/intel/iommu.h
> @@ -595,6 +595,7 @@ struct dmar_domain {
>
> spinlock_t lock; /* Protect device tracking lists */
> struct list_head devices; /* all devices' list */
> + struct list_head dev_pasids; /* all attached pasids */
>
> struct dma_pte *pgd; /* virtual address */
> int gaw; /* max guest address width */
> @@ -708,6 +709,7 @@ struct device_domain_info {
> u8 ats_supported:1;
> u8 ats_enabled:1;
> u8 dtlb_extra_inval:1; /* Quirk for devices need extra flush */
> + u8 dev_attached:1; /* Device context activated */
> u8 ats_qdep;
> struct device *dev; /* it's NULL for PCIe-to-PCI bridge */
> struct intel_iommu *iommu; /* IOMMU used by this device */
> @@ -715,6 +717,12 @@ struct device_domain_info {
> struct pasid_table *pasid_table; /* pasid table */
> };
>
> +struct device_pasid_info {
> + struct list_head link_domain; /* link to domain siblings */
> + struct device *dev; /* physical device derived from */
> + ioasid_t pasid; /* PASID on physical device */
> +};

The dev_pasids list seems to be duplicate with iommu_group::pasid_array.

The pasid_array is de facto per-device as the PCI subsystem requires ACS
to be enabled on the upstream path to the root port.

pci_enable_pasid():
385 if (!pci_acs_path_enabled(pdev, NULL, PCI_ACS_RR | PCI_ACS_UF))
386 return -EINVAL;

For such PCI topology, pci_device_group() always assigns an exclusive
iommu group (a.k.a. singleton group).

So, how about moving the pasid_array from struct iommu_group to struct
dev_iommu? With this refactoring, the individual iommu driver has no
need to create their own pasid array or list.

Instead of using iommu_group::mutex, perhaps the pasid_array needs its
own lock in struct dev_iommu after moving.

Best regards,
baolu

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