intel-iommu: Introduce domain_sg_mapping() to speed up intel_map_sg()

Instead of calling domain_pfn_mapping() repeatedly with single or
small numbers of pages, just pass the sglist in. It can optimise the
number of cache flushes like domain_pfn_mapping() does, and gives a huge
speedup for large scatterlists.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 62 insertions, 21 deletions

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 11a23201445a..28bd5f2d78fc 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -1635,6 +1635,56 @@ static int domain_context_mapped(struct pci_dev *pdev)
                                              tmp->devfn);
 }
 
+static int domain_sg_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
+                             struct scatterlist *sg, unsigned long nr_pages,
+                             int prot)
+{
+        struct dma_pte *first_pte = NULL, *pte = NULL;
+        uint64_t pteval;
+        int addr_width = agaw_to_width(domain->agaw) - VTD_PAGE_SHIFT;
+        unsigned long sg_res = 0;
+
+        BUG_ON(addr_width < BITS_PER_LONG && (iov_pfn + nr_pages - 1) >> addr_width);
+
+        if ((prot & (DMA_PTE_READ|DMA_PTE_WRITE)) == 0)
+                return -EINVAL;
+
+        prot &= DMA_PTE_READ | DMA_PTE_WRITE | DMA_PTE_SNP;
+
+        while (nr_pages--) {
+                if (!sg_res) {
+                        sg_res = (sg->offset + sg->length + VTD_PAGE_SIZE - 1) >> VTD_PAGE_SHIFT;
+                        sg->dma_address = ((dma_addr_t)iov_pfn << VTD_PAGE_SHIFT) + sg->offset;
+                        sg->dma_length = sg->length;
+                        pteval = page_to_phys(sg_page(sg)) | prot;
+                }
+                if (!pte) {
+                        first_pte = pte = pfn_to_dma_pte(domain, iov_pfn);
+                        if (!pte)
+                                return -ENOMEM;
+                }
+                /* We don't need lock here, nobody else
+                 * touches the iova range
+                 */
+                BUG_ON(dma_pte_addr(pte));
+                pte->val = pteval;
+                pte++;
+                if (!nr_pages ||
+                    (unsigned long)pte >> VTD_PAGE_SHIFT !=
+                    (unsigned long)first_pte >> VTD_PAGE_SHIFT) {
+                        domain_flush_cache(domain, first_pte,
+                                           (void *)pte - (void *)first_pte);
+                        pte = NULL;
+                }
+                iov_pfn++;
+                pteval += VTD_PAGE_SIZE;
+                sg_res--;
+                if (!sg_res)
+                        sg = sg_next(sg);
+        }
+        return 0;
+}
+
 static int domain_pfn_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
                               unsigned long phys_pfn, unsigned long nr_pages,
                               int prot)
@@ -2758,27 +2808,18 @@ static int intel_map_sg(struct device *hwdev, struct scatterlist *sglist, int ne
                 prot |= DMA_PTE_WRITE;
 
         start_vpfn = mm_to_dma_pfn(iova->pfn_lo);
-        offset_pfn = 0;
-        for_each_sg(sglist, sg, nelems, i) {
-                int nr_pages = aligned_nrpages(sg->offset, sg->length);
-                ret = domain_pfn_mapping(domain, start_vpfn + offset_pfn,
-                                         page_to_dma_pfn(sg_page(sg)),
-                                         nr_pages, prot);
-                if (ret) {
-                        /*  clear the page */
-                        dma_pte_clear_range(domain, start_vpfn,
-                                            start_vpfn + offset_pfn);
-                        /* free page tables */
-                        dma_pte_free_pagetable(domain, start_vpfn,
-                                               start_vpfn + offset_pfn);
-                        /* free iova */
-                        __free_iova(&domain->iovad, iova);
-                        return 0;
-                }
-                sg->dma_address = ((dma_addr_t)(start_vpfn + offset_pfn)
-                                   << VTD_PAGE_SHIFT) + sg->offset;
-                sg->dma_length = sg->length;
-                offset_pfn += nr_pages;
+
+        ret = domain_sg_mapping(domain, start_vpfn, sglist, mm_to_dma_pfn(size), prot);
+        if (unlikely(ret)) {
+                /*  clear the page */
+                dma_pte_clear_range(domain, start_vpfn,
+                                    start_vpfn + size - 1);
+                /* free page tables */
+                dma_pte_free_pagetable(domain, start_vpfn,
+                                       start_vpfn + size - 1);
+                /* free iova */
+                __free_iova(&domain->iovad, iova);
+                return 0;
         }
 
         /* it's a non-present to present mapping. Only flush if caching mode */