[PATCH 09 of 14] swiotlb: support bouncing of HighMem pages

Jeremy Fitzhardinge
2008-12-16T20:23:32Z

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>
---
lib/swiotlb.c | 120 +++++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 88 insertions(+), 32 deletions(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
--- 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 @@
* 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 @@
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 @@
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 @@
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 @@
return addr >= io_tlb_start && addr < io_tlb_end;
}

+static struct swiotlb_phys_addr swiotlb_bus_to_phys_addr(char *dma_addr)
+{
+ 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(char *buffer, char *dma_addr, size_t size, int dir)
+__sync_single(struct swiotlb_phys_addr buffer, char *dma_addr, size_t size, int dir)
{
- if (dir == DMA_TO_DEVICE)
- memcpy(dma_addr, buffer, size);
- else
- memcpy(buffer, dma_addr, size);
+ 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 @@
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 @@
* 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 @@
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 @@
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:
@@ -525,7 +573,10 @@
* 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;
}
@@ -593,6 +644,7 @@
{
dma_addr_t dev_addr = swiotlb_virt_to_bus(ptr);
void *map;
+ struct swiotlb_phys_addr buffer;

BUG_ON(dir == DMA_NONE);
/*
@@ -607,7 +659,9 @@
/*
* 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;
@@ -752,18 +806,20 @@
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. */
@@ -803,11 +859,11 @@
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);
@@ -836,11 +892,11 @@
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);
}
}