RE: [PATCH v12 2/8] iommu/vt-d: Use a helper function to skip agaw for SL

Tian, Kevin
2020-04-23T07:30:15Z

> From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Sent: Wednesday, April 22, 2020 2:53 AM
>
> An Intel iommu domain uses 5-level page table by default. If the
> iommu that the domain tries to attach supports less page levels,
> the top level page tables should be skipped. Add a helper to do
> this so that it could be used in other places.
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> ---
> drivers/iommu/intel-pasid.c | 33 +++++++++++++++++++++++----------
> 1 file changed, 23 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iommu/intel-pasid.c b/drivers/iommu/intel-pasid.c
> index 22b30f10b396..d9cea3011b58 100644
> --- a/drivers/iommu/intel-pasid.c
> +++ b/drivers/iommu/intel-pasid.c
> @@ -500,6 +500,25 @@ int intel_pasid_setup_first_level(struct intel_iommu
> *iommu,
> }
>
> /*
> + * Skip top levels of page tables for iommu which has less agaw
> + * than default. Unnecessary for PT mode.
> + */
> +static inline int iommu_skip_agaw(struct dmar_domain *domain,
> + struct intel_iommu *iommu,
> + struct dma_pte **pgd)
> +{
> + int agaw;
> +
> + for (agaw = domain->agaw; agaw > iommu->agaw; agaw--) {
> + *pgd = phys_to_virt(dma_pte_addr(*pgd));
> + if (!dma_pte_present(*pgd))
> + return -EINVAL;
> + }
> +
> + return agaw;
> +}
> +
> +/*
> * Set up the scalable mode pasid entry for second only translation type.
> */
> int intel_pasid_setup_second_level(struct intel_iommu *iommu,
> @@ -522,17 +541,11 @@ int intel_pasid_setup_second_level(struct
> intel_iommu *iommu,
> return -EINVAL;
> }
>
> - /*
> - * Skip top levels of page tables for iommu which has less agaw
> - * than default. Unnecessary for PT mode.
> - */
> pgd = domain->pgd;
> - for (agaw = domain->agaw; agaw > iommu->agaw; agaw--) {
> - pgd = phys_to_virt(dma_pte_addr(pgd));
> - if (!dma_pte_present(pgd)) {
> - dev_err(dev, "Invalid domain page table\n");
> - return -EINVAL;
> - }
> + agaw = iommu_skip_agaw(domain, iommu, &pgd);
> + if (agaw < 0) {
> + dev_err(dev, "Invalid domain page table\n");
> + return -EINVAL;
> }
>
> pgd_val = virt_to_phys(pgd);
> --
> 2.7.4

Reviewed-by: Kevin Tian <kevin.tian@intel.com>