swiotlb: support bouncing of HighMem pages

Impact: prepare the swiotlb code for HighMem struct pages

This requires us to treat DMA regions in terms of page+offset rather
than virtual addressing since a HighMem page may not have a mapping.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 89 insertions, 33 deletions

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index a0b4039e2880..1661af593914 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -26,6 +26,7 @@
 #include <linux/swiotlb.h>
 #include <linux/types.h>
 #include <linux/ctype.h>
+#include <linux/highmem.h>
 
 #include <asm/io.h>
 #include <asm/dma.h>
@@ -38,9 +39,6 @@
 #define OFFSET(val,align) ((unsigned long)      \
                            ( (val) & ( (align) - 1)))
 
-#define SG_ENT_VIRT_ADDRESS(sg) (sg_virt((sg)))
-#define SG_ENT_PHYS_ADDRESS(sg) virt_to_bus(SG_ENT_VIRT_ADDRESS(sg))
-
 #define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
 
 /*
@@ -91,7 +89,10 @@ static unsigned int io_tlb_index;
  * We need to save away the original address corresponding to a mapped entry
  * for the sync operations.
  */
-static unsigned char **io_tlb_orig_addr;
+static struct swiotlb_phys_addr {
+        struct page *page;
+        unsigned int offset;
+} *io_tlb_orig_addr;
 
 /*
  * Protect the above data structures in the map and unmap calls
@@ -150,6 +151,11 @@ int __weak swiotlb_arch_range_needs_mapping(void *ptr, size_t size)
         return 0;
 }
 
+static dma_addr_t swiotlb_sg_to_bus(struct scatterlist *sg)
+{
+        return swiotlb_phys_to_bus(page_to_phys(sg_page(sg)) + sg->offset);
+}
+
 /*
  * Statically reserve bounce buffer space and initialize bounce buffer data
  * structures for the software IO TLB used to implement the DMA API.
@@ -183,7 +189,7 @@ swiotlb_init_with_default_size(size_t default_size)
         for (i = 0; i < io_tlb_nslabs; i++)
                 io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
         io_tlb_index = 0;
-        io_tlb_orig_addr = alloc_bootmem(io_tlb_nslabs * sizeof(char *));
+        io_tlb_orig_addr = alloc_bootmem(io_tlb_nslabs * sizeof(struct swiotlb_phys_addr));
 
         /*
          * Get the overflow emergency buffer
@@ -258,12 +264,12 @@ swiotlb_late_init_with_default_size(size_t default_size)
                 io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
         io_tlb_index = 0;
 
-        io_tlb_orig_addr = (unsigned char **)__get_free_pages(GFP_KERNEL,
-                                   get_order(io_tlb_nslabs * sizeof(char *)));
+        io_tlb_orig_addr = (struct swiotlb_phys_addr *)__get_free_pages(GFP_KERNEL,
+                                   get_order(io_tlb_nslabs * sizeof(struct swiotlb_phys_addr)));
         if (!io_tlb_orig_addr)
                 goto cleanup3;
 
-        memset(io_tlb_orig_addr, 0, io_tlb_nslabs * sizeof(char *));
+        memset(io_tlb_orig_addr, 0, io_tlb_nslabs * sizeof(struct swiotlb_phys_addr));
 
         /*
          * Get the overflow emergency buffer
@@ -312,20 +318,59 @@ static int is_swiotlb_buffer(char *addr)
         return addr >= io_tlb_start && addr < io_tlb_end;
 }
 
-static void
-__sync_single(char *buffer, char *dma_addr, size_t size, int dir)
+static struct swiotlb_phys_addr swiotlb_bus_to_phys_addr(char *dma_addr)
 {
-        if (dir == DMA_TO_DEVICE)
-                memcpy(dma_addr, buffer, size);
-        else
-                memcpy(buffer, dma_addr, size);
+        int index = (dma_addr - io_tlb_start) >> IO_TLB_SHIFT;
+        struct swiotlb_phys_addr buffer = io_tlb_orig_addr[index];
+        buffer.offset += (long)dma_addr & ((1 << IO_TLB_SHIFT) - 1);
+        buffer.page += buffer.offset >> PAGE_SHIFT;
+        buffer.offset &= PAGE_SIZE - 1;
+        return buffer;
+}
+
+static void
+__sync_single(struct swiotlb_phys_addr buffer, char *dma_addr, size_t size, int dir)
+{
+        if (PageHighMem(buffer.page)) {
+                size_t len, bytes;
+                char *dev, *host, *kmp;
+
+                len = size;
+                while (len != 0) {
+                        unsigned long flags;
+
+                        bytes = len;
+                        if ((bytes + buffer.offset) > PAGE_SIZE)
+                                bytes = PAGE_SIZE - buffer.offset;
+                        local_irq_save(flags); /* protects KM_BOUNCE_READ */
+                        kmp  = kmap_atomic(buffer.page, KM_BOUNCE_READ);
+                        dev  = dma_addr + size - len;
+                        host = kmp + buffer.offset;
+                        if (dir == DMA_FROM_DEVICE)
+                                memcpy(host, dev, bytes);
+                        else
+                                memcpy(dev, host, bytes);
+                        kunmap_atomic(kmp, KM_BOUNCE_READ);
+                        local_irq_restore(flags);
+                        len -= bytes;
+                        buffer.page++;
+                        buffer.offset = 0;
+                }
+        } else {
+                void *v = page_address(buffer.page) + buffer.offset;
+
+                if (dir == DMA_TO_DEVICE)
+                        memcpy(dma_addr, v, size);
+                else
+                        memcpy(v, dma_addr, size);
+        }
 }
 
 /*
  * Allocates bounce buffer and returns its kernel virtual address.
  */
 static void *
-map_single(struct device *hwdev, char *buffer, size_t size, int dir)
+map_single(struct device *hwdev, struct swiotlb_phys_addr buffer, size_t size, int dir)
 {
         unsigned long flags;
         char *dma_addr;
@@ -335,6 +380,7 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir)
         unsigned long mask;
         unsigned long offset_slots;
         unsigned long max_slots;
+        struct swiotlb_phys_addr slot_buf;
 
         mask = dma_get_seg_boundary(hwdev);
         start_dma_addr = swiotlb_virt_to_bus(io_tlb_start) & mask;
@@ -419,8 +465,13 @@ found:
          * This is needed when we sync the memory.  Then we sync the buffer if
          * needed.
          */
-        for (i = 0; i < nslots; i++)
-                io_tlb_orig_addr[index+i] = buffer + (i << IO_TLB_SHIFT);
+        slot_buf = buffer;
+        for (i = 0; i < nslots; i++) {
+                slot_buf.page += slot_buf.offset >> PAGE_SHIFT;
+                slot_buf.offset &= PAGE_SIZE - 1;
+                io_tlb_orig_addr[index+i] = slot_buf;
+                slot_buf.offset += 1 << IO_TLB_SHIFT;
+        }
         if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
                 __sync_single(buffer, dma_addr, size, DMA_TO_DEVICE);
 
@@ -436,12 +487,12 @@ unmap_single(struct device *hwdev, char *dma_addr, size_t size, int dir)
         unsigned long flags;
         int i, count, nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
         int index = (dma_addr - io_tlb_start) >> IO_TLB_SHIFT;
-        char *buffer = io_tlb_orig_addr[index];
+        struct swiotlb_phys_addr buffer = swiotlb_bus_to_phys_addr(dma_addr);
 
         /*
          * First, sync the memory before unmapping the entry
          */
-        if (buffer && ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL)))
+        if ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL))
                 /*
                  * bounce... copy the data back into the original buffer * and
                  * delete the bounce buffer.
@@ -478,10 +529,7 @@ static void
 sync_single(struct device *hwdev, char *dma_addr, size_t size,
             int dir, int target)
 {
-        int index = (dma_addr - io_tlb_start) >> IO_TLB_SHIFT;
-        char *buffer = io_tlb_orig_addr[index];
-
-        buffer += ((unsigned long)dma_addr & ((1 << IO_TLB_SHIFT) - 1));
+        struct swiotlb_phys_addr buffer = swiotlb_bus_to_phys_addr(dma_addr);
 
         switch (target) {
         case SYNC_FOR_CPU:
@@ -529,7 +577,10 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                  * swiotlb_map_single(), which will grab memory from
                  * the lowest available address range.
                  */
-                ret = map_single(hwdev, NULL, size, DMA_FROM_DEVICE);
+                struct swiotlb_phys_addr buffer;
+                buffer.page = virt_to_page(NULL);
+                buffer.offset = 0;
+                ret = map_single(hwdev, buffer, size, DMA_FROM_DEVICE);
                 if (!ret)
                         return NULL;
         }
@@ -597,6 +648,7 @@ swiotlb_map_single_attrs(struct device *hwdev, void *ptr, size_t size,
 {
         dma_addr_t dev_addr = swiotlb_virt_to_bus(ptr);
         void *map;
+        struct swiotlb_phys_addr buffer;
 
         BUG_ON(dir == DMA_NONE);
         /*
@@ -611,7 +663,9 @@ swiotlb_map_single_attrs(struct device *hwdev, void *ptr, size_t size,
         /*
          * Oh well, have to allocate and map a bounce buffer.
          */
-        map = map_single(hwdev, ptr, size, dir);
+        buffer.page   = virt_to_page(ptr);
+        buffer.offset = (unsigned long)ptr & ~PAGE_MASK;
+        map = map_single(hwdev, buffer, size, dir);
         if (!map) {
                 swiotlb_full(hwdev, size, dir, 1);
                 map = io_tlb_overflow_buffer;
@@ -756,18 +810,20 @@ swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
                      int dir, struct dma_attrs *attrs)
 {
         struct scatterlist *sg;
-        void *addr;
+        struct swiotlb_phys_addr buffer;
         dma_addr_t dev_addr;
         int i;
 
         BUG_ON(dir == DMA_NONE);
 
         for_each_sg(sgl, sg, nelems, i) {
-                addr = SG_ENT_VIRT_ADDRESS(sg);
-                dev_addr = swiotlb_virt_to_bus(addr);
+                dev_addr = swiotlb_sg_to_bus(sg);
                 if (range_needs_mapping(sg_virt(sg), sg->length) ||
                     address_needs_mapping(hwdev, dev_addr, sg->length)) {
-                        void *map = map_single(hwdev, addr, sg->length, dir);
+                        void *map;
+                        buffer.page   = sg_page(sg);
+                        buffer.offset = sg->offset;
+                        map = map_single(hwdev, buffer, sg->length, dir);
                         if (!map) {
                                 /* Don't panic here, we expect map_sg users
                                    to do proper error handling. */
@@ -807,11 +863,11 @@ swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
         BUG_ON(dir == DMA_NONE);
 
         for_each_sg(sgl, sg, nelems, i) {
-                if (sg->dma_address != SG_ENT_PHYS_ADDRESS(sg))
+                if (sg->dma_address != swiotlb_sg_to_bus(sg))
                         unmap_single(hwdev, swiotlb_bus_to_virt(sg->dma_address),
                                      sg->dma_length, dir);
                 else if (dir == DMA_FROM_DEVICE)
-                        dma_mark_clean(SG_ENT_VIRT_ADDRESS(sg), sg->dma_length);
+                        dma_mark_clean(swiotlb_bus_to_virt(sg->dma_address), sg->dma_length);
         }
 }
 EXPORT_SYMBOL(swiotlb_unmap_sg_attrs);
@@ -840,11 +896,11 @@ swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
         BUG_ON(dir == DMA_NONE);
 
         for_each_sg(sgl, sg, nelems, i) {
-                if (sg->dma_address != SG_ENT_PHYS_ADDRESS(sg))
+                if (sg->dma_address != swiotlb_sg_to_bus(sg))
                         sync_single(hwdev, swiotlb_bus_to_virt(sg->dma_address),
                                     sg->dma_length, dir, target);
                 else if (dir == DMA_FROM_DEVICE)
-                        dma_mark_clean(SG_ENT_VIRT_ADDRESS(sg), sg->dma_length);
+                        dma_mark_clean(swiotlb_bus_to_virt(sg->dma_address), sg->dma_length);
         }
 }