[PATCH 31/33] dma-direct: reject too small dma masks
From: robin.murphy@arm.com (Robin Murphy)
Date: 2018-01-10 11:49:44
Also in:
linux-alpha, linux-arch, linux-iommu, linux-m68k, linux-mips, linux-s390, linux-sh, linuxppc-dev, lkml, sparclinux
On 10/01/18 08:00, Christoph Hellwig wrote:
quoted hunk ↗ jump to hunk
Signed-off-by: Christoph Hellwig <hch@lst.de> --- include/linux/dma-direct.h | 1 + lib/dma-direct.c | 19 +++++++++++++++++++ 2 files changed, 20 insertions(+)diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h index 4788bf0bf683..bcdb1a3e4b1f 100644 --- a/include/linux/dma-direct.h +++ b/include/linux/dma-direct.h@@ -42,5 +42,6 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs); void dma_direct_free(struct device *dev, size_t size, void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs); +int dma_direct_supported(struct device *dev, u64 mask); #endif /* _LINUX_DMA_DIRECT_H */diff --git a/lib/dma-direct.c b/lib/dma-direct.c index 784a68dfdbe3..40b1f92f2214 100644 --- a/lib/dma-direct.c +++ b/lib/dma-direct.c@@ -122,6 +122,24 @@ static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, return nents; } +int dma_direct_supported(struct device *dev, u64 mask) +{ +#ifdef CONFIG_ZONE_DMA + if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS)) + return 0; +#else + /* + * Because 32-bit DMA masks are so common we expect every architecture + * to be able to satisfy them - either by not supporting more physical + * memory, or by providing a ZONE_DMA32. If neither is the case, the + * architecture needs to use an IOMMU instead of the direct mapping. + */ + if (mask < DMA_BIT_MASK(32)) + return 0;
Do you think it's worth the effort to be a little more accommodating here? i.e.: return dma_max_pfn(dev) >= max_pfn; We seem to have a fair few 28-31 bit masks for older hardware which probably associates with host systems packing equivalently small amounts of RAM. Otherwise though, Reviewed-by: Robin Murphy <robin.murphy@arm.com> Robin.
quoted hunk ↗ jump to hunk
+#endif + return 1; +} + static int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr) { return dma_addr == DIRECT_MAPPING_ERROR;@@ -132,6 +150,7 @@ const struct dma_map_ops dma_direct_ops = { .free = dma_direct_free, .map_page = dma_direct_map_page, .map_sg = dma_direct_map_sg, + .dma_supported = dma_direct_supported, .mapping_error = dma_direct_mapping_error, }; EXPORT_SYMBOL(dma_direct_ops);