iommu/dma: Implement PCI allocation optimisation

Whilst PCI devices may have 64-bit DMA masks, they still benefit from
using 32-bit addresses wherever possible in order to avoid DAC (PCI) or
longer address packets (PCIe), which may incur a performance overhead.
Implement the same optimisation as other allocators by trying to get a
32-bit address first, only falling back to the full mask if that fails.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 15 insertions, 6 deletions

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 6c6e70c56d88..1c9ac26e3b68 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -287,19 +287,28 @@ int dma_info_to_prot(enum dma_data_direction dir, bool coherent,
 }
 
 static struct iova *__alloc_iova(struct iommu_domain *domain, size_t size,
-                dma_addr_t dma_limit)
+                dma_addr_t dma_limit, struct device *dev)
 {
         struct iova_domain *iovad = cookie_iovad(domain);
         unsigned long shift = iova_shift(iovad);
         unsigned long length = iova_align(iovad, size) >> shift;
+        struct iova *iova = NULL;
 
         if (domain->geometry.force_aperture)
                 dma_limit = min(dma_limit, domain->geometry.aperture_end);
+
+        /* Try to get PCI devices a SAC address */
+        if (dma_limit > DMA_BIT_MASK(32) && dev_is_pci(dev))
+                iova = alloc_iova(iovad, length, DMA_BIT_MASK(32) >> shift,
+                                  true);
         /*
          * Enforce size-alignment to be safe - there could perhaps be an
          * attribute to control this per-device, or at least per-domain...
          */
-        return alloc_iova(iovad, length, dma_limit >> shift, true);
+        if (!iova)
+                iova = alloc_iova(iovad, length, dma_limit >> shift, true);
+
+        return iova;
 }
 
 /* The IOVA allocator knows what we mapped, so just unmap whatever that was */
@@ -452,7 +461,7 @@ struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
         if (!pages)
                 return NULL;
 
-        iova = __alloc_iova(domain, size, dev->coherent_dma_mask);
+        iova = __alloc_iova(domain, size, dev->coherent_dma_mask, dev);
         if (!iova)
                 goto out_free_pages;
 
@@ -523,7 +532,7 @@ static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
         struct iova_domain *iovad = cookie_iovad(domain);
         size_t iova_off = iova_offset(iovad, phys);
         size_t len = iova_align(iovad, size + iova_off);
-        struct iova *iova = __alloc_iova(domain, len, dma_get_mask(dev));
+        struct iova *iova = __alloc_iova(domain, len, dma_get_mask(dev), dev);
 
         if (!iova)
                 return DMA_ERROR_CODE;
@@ -681,7 +690,7 @@ int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
                 prev = s;
         }
 
-        iova = __alloc_iova(domain, iova_len, dma_get_mask(dev));
+        iova = __alloc_iova(domain, iova_len, dma_get_mask(dev), dev);
         if (!iova)
                 goto out_restore_sg;
 
@@ -761,7 +770,7 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
 
         msi_page->phys = msi_addr;
         if (iovad) {
-                iova = __alloc_iova(domain, size, dma_get_mask(dev));
+                iova = __alloc_iova(domain, size, dma_get_mask(dev), dev);
                 if (!iova)
                         goto out_free_page;
                 msi_page->iova = iova_dma_addr(iovad, iova);