Re: [PATCH v8 02/10] iommu/vt-d: Add nested translation helper function

Jacob Pan
2020-01-09T18:34:06Z

On Wed, 18 Dec 2019 10:41:53 +0800
Lu Baolu <baolu.lu@linux.intel.com> wrote:

> Hi again,
>
> On 12/17/19 3:24 AM, Jacob Pan wrote:
> > +/**
> > + * intel_pasid_setup_nested() - Set up PASID entry for nested
> > translation
> > + * which is used for vSVA. The first level page tables are used for
> > + * GVA-GPA or GIOVA-GPA translation in the guest, second level
> > page tables
> > + * are used for GPA-HPA translation.
> > + *
> > + * @iommu: Iommu which the device belong to
> > + * @dev: Device to be set up for translation
> > + * @gpgd: FLPTPTR: First Level Page translation pointer in
> > GPA
> > + * @pasid: PASID to be programmed in the device PASID table
> > + * @pasid_data: Additional PASID info from the guest bind request
> > + * @domain: Domain info for setting up second level page tables
> > + * @addr_width: Address width of the first level (guest)
> > + */
> > +int intel_pasid_setup_nested(struct intel_iommu *iommu,
> > + struct device *dev, pgd_t *gpgd,
> > + int pasid, struct
> > iommu_gpasid_bind_data_vtd *pasid_data,
> > + struct dmar_domain *domain,
> > + int addr_width)
> > +{
> > + struct pasid_entry *pte;
> > + struct dma_pte *pgd;
> > + u64 pgd_val;
> > + int agaw;
> > + u16 did;
> > +
> > + if (!ecap_nest(iommu->ecap)) {
> > + pr_err("IOMMU: %s: No nested translation
> > support\n",
> > + iommu->name);
> > + return -EINVAL;
> > + }
> > +
> > + pte = intel_pasid_get_entry(dev, pasid);
> > + if (WARN_ON(!pte))
> > + return -EINVAL;
> > +
> > + pasid_clear_entry(pte);
>
> In some cases, e.g. nested mode for GIOVA-HPA, the PASID entry might
> have already been setup for second level translation. (This could be
> checked with the Present bit.) Hence, it's safe to flush caches here.
>
> Or, maybe intel_pasid_tear_down_entry() is more suitable?
>
We don't allow binding the same device-PASID twice, so if the PASID
entry was used for GIOVA/RID2PASID, it should unbind first, and
teardown flush included, right?

> Best regards,
> baolu

[Jacob Pan]