swiotlb: Return physical addresses when calling swiotlb_tbl_map_single

This change makes it so that swiotlb_tbl_map_single will return a physical
address instead of a virtual address when called.  The advantage to this once
again is that we are avoiding a number of virt_to_phys and phys_to_virt
translations by working with everything as a physical address.

One change I had to make in order to support using physical addresses is that
I could no longer trust 0 to be a invalid physical address on all platforms.
So instead I made it so that ~0 is returned on error.  This should never be a
valid return value as it implies that only one byte would be available for
use.

In order to clarify things since we now have 2 physical addresses in use
inside of swiotlb_tbl_map_single I am renaming phys to orig_addr, and
dma_addr to tlb_addr.  This way is should be clear that orig_addr is
contained within io_orig_addr and tlb_addr is an address within the
io_tlb_addr buffer.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 58db6df..8a6035a 100644 (file)
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -338,9 +338,8 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
                                enum dma_data_direction dir,
                                struct dma_attrs *attrs)
 {
-       phys_addr_t phys = page_to_phys(page) + offset;
+       phys_addr_t map, phys = page_to_phys(page) + offset;
        dma_addr_t dev_addr = xen_phys_to_bus(phys);
-       void *map;
 
        BUG_ON(dir == DMA_NONE);
        /*
@@ -356,16 +355,16 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
         * Oh well, have to allocate and map a bounce buffer.
         */
        map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir);
-       if (!map)
+       if (map == SWIOTLB_MAP_ERROR)
                return DMA_ERROR_CODE;
 
-       dev_addr = xen_virt_to_bus(map);
+       dev_addr = xen_phys_to_bus(map);
 
        /*
         * Ensure that the address returned is DMA'ble
         */
        if (!dma_capable(dev, dev_addr, size)) {
-               swiotlb_tbl_unmap_single(dev, map, size, dir);
+               swiotlb_tbl_unmap_single(dev, phys_to_virt(map), size, dir);
                dev_addr = 0;
        }
        return dev_addr;
@@ -494,11 +493,12 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
                if (swiotlb_force ||
                    !dma_capable(hwdev, dev_addr, sg->length) ||
                    range_straddles_page_boundary(paddr, sg->length)) {
-                       void *map = swiotlb_tbl_map_single(hwdev,
-                                                          start_dma_addr,
-                                                          sg_phys(sg),
-                                                          sg->length, dir);
-                       if (!map) {
+                       phys_addr_t map = swiotlb_tbl_map_single(hwdev,
+                                                                start_dma_addr,
+                                                                sg_phys(sg),
+                                                                sg->length,
+                                                                dir);
+                       if (map == SWIOTLB_MAP_ERROR) {
                                /* Don't panic here, we expect map_sg users
                                   to do proper error handling. */
                                xen_swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
@@ -506,7 +506,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
                                sgl[0].dma_length = 0;
                                return DMA_ERROR_CODE;
                        }
-                       sg->dma_address = xen_virt_to_bus(map);
+                       sg->dma_address = xen_phys_to_bus(map);
                } else
                        sg->dma_address = dev_addr;
                sg->dma_length = sg->length;

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 8d08b3e..1995f3e 100644 (file)
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -34,9 +34,14 @@ enum dma_sync_target {
        SYNC_FOR_CPU = 0,
        SYNC_FOR_DEVICE = 1,
 };
-extern void *swiotlb_tbl_map_single(struct device *hwdev, dma_addr_t tbl_dma_addr,
-                                   phys_addr_t phys, size_t size,
-                                   enum dma_data_direction dir);
+
+/* define the last possible byte of physical address space as a mapping error */
+#define SWIOTLB_MAP_ERROR (~(phys_addr_t)0x0)
+
+extern phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
+                                         dma_addr_t tbl_dma_addr,
+                                         phys_addr_t phys, size_t size,
+                                         enum dma_data_direction dir);
 
 extern void swiotlb_tbl_unmap_single(struct device *hwdev, char *dma_addr,
                                     size_t size, enum dma_data_direction dir);

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index f8c0d4e..3adc148 100644 (file)
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -393,12 +393,13 @@ void swiotlb_bounce(phys_addr_t phys, char *dma_addr, size_t size,
 }
 EXPORT_SYMBOL_GPL(swiotlb_bounce);
 
-void *swiotlb_tbl_map_single(struct device *hwdev, dma_addr_t tbl_dma_addr,
-                            phys_addr_t phys, size_t size,
-                            enum dma_data_direction dir)
+phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
+                                  dma_addr_t tbl_dma_addr,
+                                  phys_addr_t orig_addr, size_t size,
+                                  enum dma_data_direction dir)
 {
        unsigned long flags;
-       char *dma_addr;
+       phys_addr_t tlb_addr;
        unsigned int nslots, stride, index, wrap;
        int i;
        unsigned long mask;
@@ -462,7 +463,7 @@ void *swiotlb_tbl_map_single(struct device *hwdev, dma_addr_t tbl_dma_addr,
                                io_tlb_list[i] = 0;
                        for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE - 1) && io_tlb_list[i]; i--)
                                io_tlb_list[i] = ++count;
-                       dma_addr = (char *)phys_to_virt(io_tlb_start) + (index << IO_TLB_SHIFT);
+                       tlb_addr = io_tlb_start + (index << IO_TLB_SHIFT);
 
                        /*
                         * Update the indices to avoid searching in the next
@@ -480,7 +481,7 @@ void *swiotlb_tbl_map_single(struct device *hwdev, dma_addr_t tbl_dma_addr,
 
 not_found:
        spin_unlock_irqrestore(&io_tlb_lock, flags);
-       return NULL;
+       return SWIOTLB_MAP_ERROR;
 found:
        spin_unlock_irqrestore(&io_tlb_lock, flags);
 
@@ -490,11 +491,12 @@ found:
         * needed.
         */
        for (i = 0; i < nslots; i++)
-               io_tlb_orig_addr[index+i] = phys + (i << IO_TLB_SHIFT);
+               io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT);
        if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
-               swiotlb_bounce(phys, dma_addr, size, DMA_TO_DEVICE);
+               swiotlb_bounce(orig_addr, phys_to_virt(tlb_addr), size,
+                              DMA_TO_DEVICE);
 
-       return dma_addr;
+       return tlb_addr;
 }
 EXPORT_SYMBOL_GPL(swiotlb_tbl_map_single);
 
@@ -502,9 +504,8 @@ EXPORT_SYMBOL_GPL(swiotlb_tbl_map_single);
  * Allocates bounce buffer and returns its kernel virtual address.
  */
 
-static void *
-map_single(struct device *hwdev, phys_addr_t phys, size_t size,
-          enum dma_data_direction dir)
+phys_addr_t map_single(struct device *hwdev, phys_addr_t phys, size_t size,
+                      enum dma_data_direction dir)
 {
        dma_addr_t start_dma_addr = phys_to_dma(hwdev, io_tlb_start);
 
@@ -598,12 +599,15 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                dma_mask = hwdev->coherent_dma_mask;
 
        ret = (void *)__get_free_pages(flags, order);
-       if (ret && swiotlb_virt_to_bus(hwdev, ret) + size - 1 > dma_mask) {
-               /*
-                * The allocated memory isn't reachable by the device.
-                */
-               free_pages((unsigned long) ret, order);
-               ret = NULL;
+       if (ret) {
+               dev_addr = swiotlb_virt_to_bus(hwdev, ret);
+               if (dev_addr + size - 1 > dma_mask) {
+                       /*
+                        * The allocated memory isn't reachable by the device.
+                        */
+                       free_pages((unsigned long) ret, order);
+                       ret = NULL;
+               }
        }
        if (!ret) {
                /*
@@ -611,13 +615,13 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                 * GFP_DMA memory; fall back on map_single(), which
                 * will grab memory from the lowest available address range.
                 */
-               ret = map_single(hwdev, 0, size, DMA_FROM_DEVICE);
-               if (!ret)
+               phys_addr_t paddr = map_single(hwdev, 0, size, DMA_FROM_DEVICE);
+               if (paddr == SWIOTLB_MAP_ERROR)
                        return NULL;
-       }
 
-       memset(ret, 0, size);
-       dev_addr = swiotlb_virt_to_bus(hwdev, ret);
+               ret = phys_to_virt(paddr);
+               dev_addr = phys_to_dma(hwdev, paddr);
+       }
 
        /* Confirm address can be DMA'd by device */
        if (dev_addr + size - 1 > dma_mask) {
@@ -629,7 +633,10 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                swiotlb_tbl_unmap_single(hwdev, ret, size, DMA_TO_DEVICE);
                return NULL;
        }
+
        *dma_handle = dev_addr;
+       memset(ret, 0, size);
+
        return ret;
 }
 EXPORT_SYMBOL(swiotlb_alloc_coherent);
@@ -686,9 +693,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
                            enum dma_data_direction dir,
                            struct dma_attrs *attrs)
 {
-       phys_addr_t phys = page_to_phys(page) + offset;
+       phys_addr_t map, phys = page_to_phys(page) + offset;
        dma_addr_t dev_addr = phys_to_dma(dev, phys);
-       void *map;
 
        BUG_ON(dir == DMA_NONE);
        /*
@@ -699,22 +705,18 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
        if (dma_capable(dev, dev_addr, size) && !swiotlb_force)
                return dev_addr;
 
-       /*
-        * Oh well, have to allocate and map a bounce buffer.
-        */
+       /* Oh well, have to allocate and map a bounce buffer. */
        map = map_single(dev, phys, size, dir);
-       if (!map) {
+       if (map == SWIOTLB_MAP_ERROR) {
                swiotlb_full(dev, size, dir, 1);
                return phys_to_dma(dev, io_tlb_overflow_buffer);
        }
 
-       dev_addr = swiotlb_virt_to_bus(dev, map);
+       dev_addr = phys_to_dma(dev, map);
 
-       /*
-        * Ensure that the address returned is DMA'ble
-        */
+       /* Ensure that the address returned is DMA'ble */
        if (!dma_capable(dev, dev_addr, size)) {
-               swiotlb_tbl_unmap_single(dev, map, size, dir);
+               swiotlb_tbl_unmap_single(dev, phys_to_virt(map), size, dir);
                return phys_to_dma(dev, io_tlb_overflow_buffer);
        }
 
@@ -840,9 +842,9 @@ swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
 
                if (swiotlb_force ||
                    !dma_capable(hwdev, dev_addr, sg->length)) {
-                       void *map = map_single(hwdev, sg_phys(sg),
-                                              sg->length, dir);
-                       if (!map) {
+                       phys_addr_t map = map_single(hwdev, sg_phys(sg),
+                                                    sg->length, dir);
+                       if (map == SWIOTLB_MAP_ERROR) {
                                /* Don't panic here, we expect map_sg users
                                   to do proper error handling. */
                                swiotlb_full(hwdev, sg->length, dir, 0);
@@ -851,7 +853,7 @@ swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
                                sgl[0].dma_length = 0;
                                return 0;
                        }
-                       sg->dma_address = swiotlb_virt_to_bus(hwdev, map);
+                       sg->dma_address = phys_to_dma(hwdev, map);
                } else
                        sg->dma_address = dev_addr;
                sg->dma_length = sg->length;