Re: [PATCH v3 4/5] dma-iommu: Check CONFIG_SWIOTLB more broadly

[Robin Murphy]

On 2021-08-11 03:42, David Stevens wrote:

From: David Stevens <steve...@chromium.org>

Introduce a new dev_use_swiotlb function to guard swiotlb code, instead
of overloading dev_is_untrusted. This allows CONFIG_SWIOTLB to be
checked more broadly, so the swiotlb related code can be removed more
aggressively.

Reviewed-by: Robin Murphy <robin.mur...@arm.com>

Signed-off-by: David Stevens <steve...@chromium.org>
---
  drivers/iommu/dma-iommu.c | 24 ++++++++++++++----------
  1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index be0214b1455c..89b689bf801f 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -317,6 +317,11 @@ static bool dev_is_untrusted(struct device *dev)
        return dev_is_pci(dev) && to_pci_dev(dev)->untrusted;
  }

+static bool dev_use_swiotlb(struct device *dev)

+{
+       return IS_ENABLED(CONFIG_SWIOTLB) && dev_is_untrusted(dev);
+}
+
  /**
   * iommu_dma_init_domain - Initialise a DMA mapping domain
   * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie()
@@ -553,8 +558,7 @@ static dma_addr_t __iommu_dma_map_swiotlb(struct device 
*dev, phys_addr_t phys,
         * If both the physical buffer start address and size are
         * page aligned, we don't need to use a bounce page.
         */
-       if (IS_ENABLED(CONFIG_SWIOTLB) && dev_is_untrusted(dev) &&
-           iova_offset(iovad, phys | org_size)) {
+       if (dev_use_swiotlb(dev) && iova_offset(iovad, phys | org_size)) {
                aligned_size = iova_align(iovad, org_size);
                phys = swiotlb_tbl_map_single(dev, phys, org_size,
                                              aligned_size, dir, attrs);
@@ -779,7 +783,7 @@ static void iommu_dma_sync_single_for_cpu(struct device 
*dev,
  {
        phys_addr_t phys;

- if (dev_is_dma_coherent(dev) && !dev_is_untrusted(dev))

+       if (dev_is_dma_coherent(dev) && !dev_use_swiotlb(dev))
                return;

phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle);

@@ -795,7 +799,7 @@ static void iommu_dma_sync_single_for_device(struct device 
*dev,
  {
        phys_addr_t phys;

- if (dev_is_dma_coherent(dev) && !dev_is_untrusted(dev))

+       if (dev_is_dma_coherent(dev) && !dev_use_swiotlb(dev))
                return;

phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle);

@@ -813,10 +817,10 @@ static void iommu_dma_sync_sg_for_cpu(struct device *dev,
        struct scatterlist *sg;
        int i;

- if (dev_is_dma_coherent(dev) && !dev_is_untrusted(dev))

+       if (dev_is_dma_coherent(dev) && !dev_use_swiotlb(dev))
                return;

- if (dev_is_untrusted(dev))

+       if (dev_use_swiotlb(dev))
                for_each_sg(sgl, sg, nelems, i)
                        iommu_dma_sync_single_for_cpu(dev, sg_dma_address(sg),
                                                      sg->length, dir);
@@ -832,10 +836,10 @@ static void iommu_dma_sync_sg_for_device(struct device 
*dev,
        struct scatterlist *sg;
        int i;

- if (dev_is_dma_coherent(dev) && !dev_is_untrusted(dev))

+       if (dev_is_dma_coherent(dev) && !dev_use_swiotlb(dev))
                return;

- if (dev_is_untrusted(dev))

+       if (dev_use_swiotlb(dev))
                for_each_sg(sgl, sg, nelems, i)
                        iommu_dma_sync_single_for_device(dev,
                                                         sg_dma_address(sg),
@@ -999,7 +1003,7 @@ static int iommu_dma_map_sg(struct device *dev, struct 
scatterlist *sg,
            iommu_deferred_attach(dev, domain))
                return 0;

- if (dev_is_untrusted(dev))

+       if (dev_use_swiotlb(dev))
                return iommu_dma_map_sg_swiotlb(dev, sg, nents, dir, attrs);

if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {

@@ -1078,7 +1082,7 @@ static void iommu_dma_unmap_sg(struct device *dev, struct 
scatterlist *sg,
                attrs |= DMA_ATTR_SKIP_CPU_SYNC;
        }

- if (dev_is_untrusted(dev)) {

+       if (dev_use_swiotlb(dev)) {
                iommu_dma_unmap_sg_swiotlb(dev, sg, nents, dir, attrs);
                return;
        }

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