[PATCH 08/10] swiotlb: don't dip into swiotlb pool for coherent allocations

Christoph Hellwig
2018-10-08T08:03:39Z

All architectures that support swiotlb also have a zone that backs up
these less than full addressing allocations (usually ZONE_DMA32).

Because of that it is rather pointless to fall back to the global swiotlb
buffer if the normal dma direct allocation failed - the only thing this
will do is to eat up bounce buffers that would be more useful to serve
streaming mappings.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/arm64/mm/dma-mapping.c | 6 +--
include/linux/swiotlb.h | 5 --
kernel/dma/swiotlb.c | 105 +-----------------------------------
3 files changed, 5 insertions(+), 111 deletions(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 8d91b927e09e..eee6cfcfde9e 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -112,7 +112,7 @@ static void *__dma_alloc(struct device *dev, size_t size,
return addr;
}

- ptr = swiotlb_alloc(dev, size, dma_handle, flags, attrs);
+ ptr = dma_direct_alloc_pages(dev, size, dma_handle, flags, attrs);
if (!ptr)
goto no_mem;

@@ -133,7 +133,7 @@ static void *__dma_alloc(struct device *dev, size_t size,
return coherent_ptr;

no_map:
- swiotlb_free(dev, size, ptr, *dma_handle, attrs);
+ dma_direct_free_pages(dev, size, ptr, *dma_handle, attrs);
no_mem:
return NULL;
}
@@ -151,7 +151,7 @@ static void __dma_free(struct device *dev, size_t size,
return;
vunmap(vaddr);
}
- swiotlb_free(dev, size, swiotlb_addr, dma_handle, attrs);
+ dma_direct_free_pages(dev, size, swiotlb_addr, dma_handle, attrs);
}

static dma_addr_t __swiotlb_map_page(struct device *dev, struct page *page,
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index f847c1b265c4..a387b59640a4 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -67,11 +67,6 @@ extern void swiotlb_tbl_sync_single(struct device *hwdev,

/* Accessory functions. */

-void *swiotlb_alloc(struct device *hwdev, size_t size, dma_addr_t *dma_handle,
- gfp_t flags, unsigned long attrs);
-void swiotlb_free(struct device *dev, size_t size, void *vaddr,
- dma_addr_t dma_addr, unsigned long attrs);
-
extern dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
unsigned long offset, size_t size,
enum dma_data_direction dir,
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 4d7a4d85d71e..475a41eff3dc 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -622,78 +622,6 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
}
}

-static inline bool dma_coherent_ok(struct device *dev, dma_addr_t addr,
- size_t size)
-{
- u64 mask = DMA_BIT_MASK(32);
-
- if (dev && dev->coherent_dma_mask)
- mask = dev->coherent_dma_mask;
- return addr + size - 1 <= mask;
-}
-
-static void *
-swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle,
- unsigned long attrs)
-{
- phys_addr_t phys_addr;
-
- if (swiotlb_force == SWIOTLB_NO_FORCE)
- goto out_warn;
-
- phys_addr = swiotlb_tbl_map_single(dev,
- __phys_to_dma(dev, io_tlb_start),
- 0, size, DMA_FROM_DEVICE, attrs);
- if (phys_addr == SWIOTLB_MAP_ERROR)
- goto out_warn;
-
- *dma_handle = __phys_to_dma(dev, phys_addr);
- if (!dma_coherent_ok(dev, *dma_handle, size))
- goto out_unmap;
-
- memset(phys_to_virt(phys_addr), 0, size);
- return phys_to_virt(phys_addr);
-
-out_unmap:
- dev_warn(dev, "hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n",
- (unsigned long long)dev->coherent_dma_mask,
- (unsigned long long)*dma_handle);
-
- /*
- * DMA_TO_DEVICE to avoid memcpy in unmap_single.
- * DMA_ATTR_SKIP_CPU_SYNC is optional.
- */
- swiotlb_tbl_unmap_single(dev, phys_addr, size, DMA_TO_DEVICE,
- DMA_ATTR_SKIP_CPU_SYNC);
-out_warn:
- if (!(attrs & DMA_ATTR_NO_WARN) && printk_ratelimit()) {
- dev_warn(dev,
- "swiotlb: coherent allocation failed, size=%zu\n",
- size);
- dump_stack();
- }
- return NULL;
-}
-
-static bool swiotlb_free_buffer(struct device *dev, size_t size,
- dma_addr_t dma_addr)
-{
- phys_addr_t phys_addr = dma_to_phys(dev, dma_addr);
-
- WARN_ON_ONCE(irqs_disabled());
-
- if (!is_swiotlb_buffer(phys_addr))
- return false;
-
- /*
- * DMA_TO_DEVICE to avoid memcpy in swiotlb_tbl_unmap_single.
- * DMA_ATTR_SKIP_CPU_SYNC is optional.
- */
- swiotlb_tbl_unmap_single(dev, phys_addr, size, DMA_TO_DEVICE,
- DMA_ATTR_SKIP_CPU_SYNC);
- return true;
-}
-
static dma_addr_t swiotlb_bounce_page(struct device *dev, phys_addr_t *phys,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
@@ -928,39 +856,10 @@ swiotlb_dma_supported(struct device *hwdev, u64 mask)
return __phys_to_dma(hwdev, io_tlb_end - 1) <= mask;
}

-void *swiotlb_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
- gfp_t gfp, unsigned long attrs)
-{
- void *vaddr;
-
- /* temporary workaround: */
- if (gfp & __GFP_NOWARN)
- attrs |= DMA_ATTR_NO_WARN;
-
- /*
- * Don't print a warning when the first allocation attempt fails.
- * swiotlb_alloc_coherent() will print a warning when the DMA memory
- * allocation ultimately failed.
- */
- gfp |= __GFP_NOWARN;
-
- vaddr = dma_direct_alloc(dev, size, dma_handle, gfp, attrs);
- if (!vaddr)
- vaddr = swiotlb_alloc_buffer(dev, size, dma_handle, attrs);
- return vaddr;
-}
-
-void swiotlb_free(struct device *dev, size_t size, void *vaddr,
- dma_addr_t dma_addr, unsigned long attrs)
-{
- if (!swiotlb_free_buffer(dev, size, dma_addr))
- dma_direct_free(dev, size, vaddr, dma_addr, attrs);
-}
-
const struct dma_map_ops swiotlb_dma_ops = {
.mapping_error = dma_direct_mapping_error,
- .alloc = swiotlb_alloc,
- .free = swiotlb_free,
+ .alloc = dma_direct_alloc,
+ .free = dma_direct_free,
.sync_single_for_cpu = swiotlb_sync_single_for_cpu,
.sync_single_for_device = swiotlb_sync_single_for_device,
.sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
--
2.19.0