RE: [PATCH v2 1/6] iommu/vt-d: Setup scalable mode context entry in probe path

Tian, Kevin
2023-12-08T08:51:19Z

> From: Lu Baolu <baolu.lu@linux.intel.com>
> Sent: Tuesday, December 5, 2023 9:22 AM
>
> @@ -304,6 +304,11 @@ int intel_pasid_setup_first_level(struct intel_iommu
> *iommu,
> return -EINVAL;
> }
>
> + if (intel_pasid_setup_sm_context(dev, true)) {
> + dev_err(dev, "Context entry is not configured\n");
> + return -ENODEV;
> + }
> +
> spin_lock(&iommu->lock);
> pte = intel_pasid_get_entry(dev, pasid);
> if (!pte) {
> @@ -384,6 +389,11 @@ int intel_pasid_setup_second_level(struct
> intel_iommu *iommu,
> return -EINVAL;
> }
>
> + if (intel_pasid_setup_sm_context(dev, true)) {
> + dev_err(dev, "Context entry is not configured\n");
> + return -ENODEV;
> + }
> +
> pgd = domain->pgd;
> agaw = iommu_skip_agaw(domain, iommu, &pgd);
> if (agaw < 0) {
> @@ -505,6 +515,11 @@ int intel_pasid_setup_pass_through(struct
> intel_iommu *iommu,
> u16 did = FLPT_DEFAULT_DID;
> struct pasid_entry *pte;
>
> + if (intel_pasid_setup_sm_context(dev, true)) {
> + dev_err(dev, "Context entry is not configured\n");
> + return -ENODEV;
> + }
> +
> spin_lock(&iommu->lock);
> pte = intel_pasid_get_entry(dev, pasid);
> if (!pte) {

instead of replicating the invocation in all three stubs it's simpler to
do once in dmar_domain_attach_device() for all of them.

Then put the deferred check outside of intel_pasid_setup_sm_context()
instead of using a Boolean flag

> @@ -623,6 +638,11 @@ int intel_pasid_setup_nested(struct intel_iommu
> *iommu, struct device *dev,
> return -EINVAL;
> }
>
> + if (intel_pasid_setup_sm_context(dev, true)) {
> + dev_err_ratelimited(dev, "Context entry is not configured\n");
> + return -ENODEV;
> + }
> +

Do we support nested in kdump?

> +
> + /*
> + * Cache invalidation for changes to a scalable-mode context table
> + * entry.
> + *
> + * Section 6.5.3.3 of the VT-d spec:
> + * - Device-selective context-cache invalidation;
> + * - Domain-selective PASID-cache invalidation to affected domains
> + * (can be skipped if all PASID entries were not-present);
> + * - Domain-selective IOTLB invalidation to affected domains;
> + * - Global Device-TLB invalidation to affected functions.
> + *
> + * For kdump cases, old valid entries may be cached due to the
> + * in-flight DMA and copied pgtable, but there is no unmapping
> + * behaviour for them, thus we need explicit cache flushes for all
> + * affected domain IDs and PASIDs used in the copied PASID table.
> + * Given that we have no idea about which domain IDs and PASIDs
> were
> + * used in the copied tables, upgrade them to global PASID and IOTLB
> + * cache invalidation.
> + *
> + * For kdump case, at this point, the device is supposed to finish
> + * reset at its driver probe stage, so no in-flight DMA will exist,
> + * and we don't need to worry anymore hereafter.
> + */
> + if (context_copied(iommu, bus, devfn)) {
> + context_clear_entry(context);
> + clear_context_copied(iommu, bus, devfn);
> + iommu->flush.flush_context(iommu, 0,
> + (((u16)bus) << 8) | devfn,
> + DMA_CCMD_MASK_NOBIT,
> + DMA_CCMD_DEVICE_INVL);
> + qi_flush_pasid_cache(iommu, 0, QI_PC_GLOBAL, 0);
> + iommu->flush.flush_iotlb(iommu, 0, 0, 0,
> DMA_TLB_GLOBAL_FLUSH);
> + devtlb_invalidation_with_pasid(iommu, dev,
> IOMMU_NO_PASID);
> + }

I don't see this logic from existing code. If it's a bug fix then
please send it separately first.

> +
> + context_entry_set_pasid_table(context, dev);

and here is additional change to the context entry. Why is the
context cache invalidated in the start?

> +
> +static int pci_pasid_table_setup(struct pci_dev *pdev, u16 alias, void *data)
> +{
> + struct device *dev = data;
> +
> + if (dev != &pdev->dev)
> + return 0;

what is it for? the existing domain_context_mapping_cb() doesn't have
this check then implying a behavior change.