Re: [PATCH 10/22] swiotlb: refactor coherent buffer allocation
From: Robin Murphy <robin.murphy@arm.com>
Date: 2018-01-10 12:22:27
Also in:
linux-arch, linux-arm-kernel, linux-iommu, linux-mips, lkml
On 10/01/18 08:09, Christoph Hellwig wrote:
quoted hunk ↗ jump to hunk
Factor out a new swiotlb_alloc_buffer helper that allocates DMA coherent memory from the swiotlb bounce buffer. This allows to simplify the swiotlb_alloc implemenation that uses dma_direct_alloc to try to allocate a reachable buffer first. Signed-off-by: Christoph Hellwig <hch@lst.de> --- lib/swiotlb.c | 122 +++++++++++++++++++++++++++++++--------------------------- 1 file changed, 65 insertions(+), 57 deletions(-)diff --git a/lib/swiotlb.c b/lib/swiotlb.c index 1a147f1354a1..bf2d19ee91c1 100644 --- a/lib/swiotlb.c +++ b/lib/swiotlb.c@@ -709,75 +709,79 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr, } EXPORT_SYMBOL_GPL(swiotlb_tbl_sync_single); -void * -swiotlb_alloc_coherent(struct device *hwdev, size_t size, - dma_addr_t *dma_handle, gfp_t flags) +static inline bool dma_coherent_ok(struct device *dev, dma_addr_t addr, + size_t size) { - bool warn = !(flags & __GFP_NOWARN); - dma_addr_t dev_addr; - void *ret; - int order = get_order(size); - u64 dma_mask = DMA_BIT_MASK(32); + u64 mask = DMA_BIT_MASK(32); - if (hwdev && hwdev->coherent_dma_mask) - dma_mask = hwdev->coherent_dma_mask; + if (dev && dev->coherent_dma_mask) + mask = dev->coherent_dma_mask; + return addr + size - 1 <= mask; +} - ret = (void *)__get_free_pages(flags, order); - 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. - */ - phys_addr_t paddr = map_single(hwdev, 0, size, DMA_FROM_DEVICE, - warn ? 0 : DMA_ATTR_NO_WARN); - if (paddr == SWIOTLB_MAP_ERROR) - goto err_warn; +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; - ret = phys_to_virt(paddr); - dev_addr = swiotlb_phys_to_dma(hwdev, paddr); + phys_addr = swiotlb_tbl_map_single(dev, + swiotlb_phys_to_dma(dev, io_tlb_start), + 0, size, DMA_FROM_DEVICE, 0); + if (phys_addr == SWIOTLB_MAP_ERROR) + goto out_warn; - /* Confirm address can be DMA'd by device */ - if (dev_addr + size - 1 > dma_mask) { - printk("hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n", - (unsigned long long)dma_mask, - (unsigned long long)dev_addr); + *dma_handle = swiotlb_phys_to_dma(dev, phys_addr);
nit: this should probably go after the dma_coherent_ok() check (as with the original logic).
- /*
- * DMA_TO_DEVICE to avoid memcpy in unmap_single.
- * The DMA_ATTR_SKIP_CPU_SYNC is optional.
- */
- swiotlb_tbl_unmap_single(hwdev, paddr,
- size, DMA_TO_DEVICE,
- DMA_ATTR_SKIP_CPU_SYNC);
- goto err_warn;
- }
- }
+ if (dma_coherent_ok(dev, *dma_handle, size))
+ goto out_unmap;
- *dma_handle = dev_addr;
- memset(ret, 0, size);
+ memset(phys_to_virt(phys_addr), 0, size);
+ return phys_to_virt(phys_addr);
- return ret;
+out_unmap:
+ dev_warn(dev, "hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n",
+ (unsigned long long)(dev ? dev->coherent_dma_mask : 0),
+ (unsigned long long)*dma_handle);
-err_warn:
- if (warn && printk_ratelimit()) {
- pr_warn("swiotlb: coherent allocation failed for device %s size=%zu\n",
- dev_name(hwdev), size);
+ /*
+ * 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;
}
+
+void *
+swiotlb_alloc_coherent(struct device *hwdev, size_t size,
+ dma_addr_t *dma_handle, gfp_t flags)
+{
+ int order = get_order(size);
+ unsigned long attrs = (flags & __GFP_NOWARN) ? DMA_ATTR_NO_WARN : 0;
+ void *ret;
+
+ ret = (void *)__get_free_pages(flags, order);
+ if (ret) {
+ *dma_handle = swiotlb_virt_to_bus(hwdev, ret);
+ if (dma_coherent_ok(hwdev, *dma_handle, size)) {
+ memset(ret, 0, size);
+ return ret;
+ }Aren't we leaking the pages here? Robin.
quoted hunk ↗ jump to hunk
+ } + + return swiotlb_alloc_buffer(hwdev, size, dma_handle, attrs); +} EXPORT_SYMBOL(swiotlb_alloc_coherent); static bool swiotlb_free_buffer(struct device *dev, size_t size,@@ -1103,6 +1107,10 @@ void *swiotlb_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle, { 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@@ -1112,7 +1120,7 @@ void *swiotlb_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle, vaddr = dma_direct_alloc(dev, size, dma_handle, gfp, attrs); if (!vaddr) - vaddr = swiotlb_alloc_coherent(dev, size, dma_handle, gfp); + vaddr = swiotlb_alloc_buffer(dev, size, dma_handle, attrs); return vaddr; }