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swiotlb: Return physical addresses when calling swiotlb_tbl_map_single
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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>
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Alexander Duyck authored and Konrad Rzeszutek Wilk committed Oct 30, 2012
1 parent ee3f6ba commit e05ed4d
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Showing 3 changed files with 59 additions and 52 deletions.
22 changes: 11 additions & 11 deletions drivers/xen/swiotlb-xen.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
/*
Expand All @@ -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;
Expand Down Expand Up @@ -494,19 +493,20 @@ 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,
attrs);
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;
Expand Down
11 changes: 8 additions & 3 deletions include/linux/swiotlb.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down
78 changes: 40 additions & 38 deletions lib/swiotlb.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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
Expand All @@ -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);

Expand All @@ -490,21 +491,21 @@ void *swiotlb_tbl_map_single(struct device *hwdev, dma_addr_t tbl_dma_addr,
* 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);

/*
* 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);

Expand Down Expand Up @@ -598,26 +599,29 @@ 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) {
/*
* We are either out of memory or the device can't DMA to
* 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) {
Expand All @@ -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);
Expand Down Expand Up @@ -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);
/*
Expand All @@ -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);
}

Expand Down Expand Up @@ -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);
Expand All @@ -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;
Expand Down

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