Allow the dma-iommu api to use bounce buffers for untrusted devices.
This is a copy of the intel bounce buffer code.

Signed-off-by: Tom Murphy <murph...@tcd.ie>
---
 drivers/iommu/dma-iommu.c   | 94 ++++++++++++++++++++++++++++++-------
 drivers/iommu/intel/iommu.c |  6 +++
 drivers/iommu/iommu.c       | 10 ++++
 include/linux/iommu.h       |  7 +++
 4 files changed, 101 insertions(+), 16 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 33f3f4f5edc5..185cd504ca5a 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -21,9 +21,11 @@
 #include <linux/mm.h>
 #include <linux/mutex.h>
 #include <linux/pci.h>
+#include <linux/swiotlb.h>
 #include <linux/scatterlist.h>
 #include <linux/vmalloc.h>
 #include <linux/crash_dump.h>
+#include <linux/dma-direct.h>
 
 struct iommu_dma_msi_page {
        struct list_head        list;
@@ -498,26 +500,87 @@ static void __iommu_dma_unmap(struct device *dev, 
dma_addr_t dma_addr,
        iommu_dma_free_iova(cookie, dma_addr, size, iotlb_gather.freelist);
 }
 
+static void __iommu_dma_unmap_swiotlb(struct device *dev, dma_addr_t dma_addr,
+               size_t size, enum dma_data_direction dir,
+               unsigned long attrs)
+{
+       struct iommu_domain *domain = iommu_get_dma_domain(dev);
+       struct iommu_dma_cookie *cookie = domain->iova_cookie;
+       struct iova_domain *iovad = &cookie->iovad;
+       size_t iova_off = iova_offset(iovad, dma_addr);
+       size_t aligned_size = iova_align(iovad, size + iova_off);
+       phys_addr_t phys;
+
+       phys = iommu_iova_to_phys(domain, dma_addr);
+       if (WARN_ON(!phys))
+               return;
+
+       __iommu_dma_unmap(dev, dma_addr, size);
+
+#ifdef CONFIG_SWIOTLB
+       if (unlikely(is_swiotlb_buffer(phys)))
+               swiotlb_tbl_unmap_single(dev, phys, size,
+                               aligned_size, dir, attrs);
+#endif
+}
+
 static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
-               size_t size, int prot, u64 dma_mask)
+               size_t org_size, dma_addr_t dma_mask, bool coherent,
+               enum dma_data_direction dir, unsigned long attrs)
 {
+       int prot = dma_info_to_prot(dir, coherent, attrs);
        struct iommu_domain *domain = iommu_get_dma_domain(dev);
        struct iommu_dma_cookie *cookie = domain->iova_cookie;
        struct iova_domain *iovad = &cookie->iovad;
        size_t iova_off = iova_offset(iovad, phys);
+       size_t aligned_size = iova_align(iovad, org_size + iova_off);
+       void *padding_start;
+       size_t padding_size;
        dma_addr_t iova;
 
        if (unlikely(iommu_dma_deferred_attach(dev, domain)))
                return DMA_MAPPING_ERROR;
 
-       size = iova_align(iovad, size + iova_off);
+#ifdef CONFIG_SWIOTLB
+       /*
+        * If both the physical buffer start address and size are
+        * page aligned, we don't need to use a bounce page.
+        */
+       if (iommu_needs_bounce_buffer(dev)
+                       && !iova_offset(iovad, phys | org_size)) {
+               phys = swiotlb_tbl_map_single(dev,
+                               __phys_to_dma(dev, io_tlb_start),
+                               phys, org_size, aligned_size, dir, attrs);
+
+               if (phys == DMA_MAPPING_ERROR)
+                       return DMA_MAPPING_ERROR;
+
+               /* Cleanup the padding area. */
+               padding_start = phys_to_virt(phys);
+               padding_size = aligned_size;
+
+               if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
+                   (dir == DMA_TO_DEVICE ||
+                    dir == DMA_BIDIRECTIONAL)) {
+                       padding_start += org_size;
+                       padding_size -= org_size;
+               }
 
-       iova = iommu_dma_alloc_iova(domain, size, dma_mask, dev);
+               memset(padding_start, 0, padding_size);
+       }
+#endif
+
+       iova = iommu_dma_alloc_iova(domain, aligned_size, dma_mask, dev);
        if (!iova)
                return DMA_MAPPING_ERROR;
 
-       if (iommu_map_atomic(domain, iova, phys - iova_off, size, prot)) {
-               iommu_dma_free_iova(cookie, iova, size, NULL);
+       if (iommu_map_atomic(domain, iova, phys - iova_off, aligned_size,
+                               prot)) {
+
+               if (unlikely(is_swiotlb_buffer(phys)))
+                       swiotlb_tbl_unmap_single(dev, phys, aligned_size,
+                                       aligned_size, dir, attrs);
+               iommu_dma_free_iova(cookie, iova, aligned_size, NULL);
                return DMA_MAPPING_ERROR;
        }
        return iova + iova_off;
@@ -751,10 +814,10 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, 
struct page *page,
 {
        phys_addr_t phys = page_to_phys(page) + offset;
        bool coherent = dev_is_dma_coherent(dev);
-       int prot = dma_info_to_prot(dir, coherent, attrs);
        dma_addr_t dma_handle;
 
-       dma_handle = __iommu_dma_map(dev, phys, size, prot, dma_get_mask(dev));
+       dma_handle = __iommu_dma_map(dev, phys, size, dma_get_mask(dev),
+                       coherent, dir, attrs);
        if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
            dma_handle != DMA_MAPPING_ERROR)
                arch_sync_dma_for_device(phys, size, dir);
@@ -766,7 +829,7 @@ static void iommu_dma_unmap_page(struct device *dev, 
dma_addr_t dma_handle,
 {
        if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
                iommu_dma_sync_single_for_cpu(dev, dma_handle, size, dir);
-       __iommu_dma_unmap(dev, dma_handle, size);
+       __iommu_dma_unmap_swiotlb(dev, dma_handle, size, dir, attrs);
 }
 
 /*
@@ -950,21 +1013,20 @@ static void iommu_dma_unmap_sg(struct device *dev, 
struct scatterlist *sg,
                sg = tmp;
        }
        end = sg_dma_address(sg) + sg_dma_len(sg);
-       __iommu_dma_unmap(dev, start, end - start);
+       __iommu_dma_unmap_swiotlb(dev, start, end - start, dir, attrs);
 }
 
 static dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
                size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
-       return __iommu_dma_map(dev, phys, size,
-                       dma_info_to_prot(dir, false, attrs) | IOMMU_MMIO,
-                       dma_get_mask(dev));
+       return __iommu_dma_map(dev, phys, size, dma_get_mask(dev), false, dir,
+                       attrs);
 }
 
 static void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
                size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
-       __iommu_dma_unmap(dev, handle, size);
+       __iommu_dma_unmap_swiotlb(dev, handle, size, dir, attrs);
 }
 
 static void __iommu_dma_free(struct device *dev, size_t size, void *cpu_addr)
@@ -1046,7 +1108,6 @@ static void *iommu_dma_alloc(struct device *dev, size_t 
size,
                dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
 {
        bool coherent = dev_is_dma_coherent(dev);
-       int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
        struct page *page = NULL;
        void *cpu_addr;
 
@@ -1065,8 +1126,9 @@ static void *iommu_dma_alloc(struct device *dev, size_t 
size,
        if (!cpu_addr)
                return NULL;
 
-       *handle = __iommu_dma_map(dev, page_to_phys(page), size, ioprot,
-                       dev->coherent_dma_mask);
+       *handle = __iommu_dma_map(dev, page_to_phys(page), size,
+                       dev->coherent_dma_mask, coherent, DMA_BIDIRECTIONAL,
+                       attrs);
        if (*handle == DMA_MAPPING_ERROR) {
                __iommu_dma_free(dev, size, cpu_addr);
                return NULL;
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 03699860880b..ba47623f0f12 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -5713,6 +5713,11 @@ static void intel_iommu_probe_finalize(struct device 
*dev)
                set_dma_ops(dev, NULL);
 }
 
+static int intel_iommu_needs_bounce_buffer(struct device *d)
+{
+       return !intel_no_bounce && dev_is_pci(d) && to_pci_dev(d)->untrusted;
+}
+
 static void intel_iommu_get_resv_regions(struct device *device,
                                         struct list_head *head)
 {
@@ -6079,6 +6084,7 @@ const struct iommu_ops intel_iommu_ops = {
        .probe_device           = intel_iommu_probe_device,
        .probe_finalize         = intel_iommu_probe_finalize,
        .release_device         = intel_iommu_release_device,
+       .needs_bounce_buffer    = intel_iommu_needs_bounce_buffer,
        .get_resv_regions       = intel_iommu_get_resv_regions,
        .put_resv_regions       = generic_iommu_put_resv_regions,
        .apply_resv_region      = intel_iommu_apply_resv_region,
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index b6858adc4f17..8da26c73122f 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2497,6 +2497,16 @@ int iommu_domain_set_attr(struct iommu_domain *domain,
 }
 EXPORT_SYMBOL_GPL(iommu_domain_set_attr);
 
+int iommu_needs_bounce_buffer(struct device *dev)
+{
+       const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+       if (ops && ops->needs_bounce_buffer)
+               return ops->needs_bounce_buffer(dev);
+
+       return 0;
+}
+
 void iommu_get_resv_regions(struct device *dev, struct list_head *list)
 {
        const struct iommu_ops *ops = dev->bus->iommu_ops;
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index e3eafb3cf4ba..4c2d2619fd8c 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -263,6 +263,7 @@ struct iommu_ops {
                               enum iommu_attr attr, void *data);
        int (*domain_set_attr)(struct iommu_domain *domain,
                               enum iommu_attr attr, void *data);
+       int (*needs_bounce_buffer)(struct device *dev);
 
        /* Request/Free a list of reserved regions for a device */
        void (*get_resv_regions)(struct device *dev, struct list_head *list);
@@ -474,6 +475,7 @@ static inline size_t iommu_map_sgtable(struct iommu_domain 
*domain,
        return iommu_map_sg(domain, iova, sgt->sgl, sgt->orig_nents, prot);
 }
 
+extern int iommu_needs_bounce_buffer(struct device *dev);
 extern void iommu_get_resv_regions(struct device *dev, struct list_head *list);
 extern void iommu_put_resv_regions(struct device *dev, struct list_head *list);
 extern void generic_iommu_put_resv_regions(struct device *dev,
@@ -779,6 +781,11 @@ static inline void iommu_set_fault_handler(struct 
iommu_domain *domain,
 {
 }
 
+static inline int iommu_needs_bounce_buffer(struct device *dev)
+{
+       return 0;
+}
+
 static inline void iommu_get_resv_regions(struct device *dev,
                                        struct list_head *list)
 {
-- 
2.20.1

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