On 09/11/2018 08:46, Christoph Hellwig wrote:
[...]
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 1167ff0416cf..cfb422e17049 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -55,8 +55,6 @@
#include "amd_iommu_types.h"
#include "irq_remapping.h"
-#define AMD_IOMMU_MAPPING_ERROR 0
-
#define CMD_SET_TYPE(cmd, t) ((cmd)->data[1] |= ((t) << 28))
#define LOOP_TIMEOUT 100000
@@ -2339,7 +2337,7 @@ static dma_addr_t __map_single(struct device *dev,
paddr &= PAGE_MASK;
address = dma_ops_alloc_iova(dev, dma_dom, pages, dma_mask);
- if (address == AMD_IOMMU_MAPPING_ERROR)
+ if (address == DMA_MAPPING_ERROR)
This for one is clearly broken, because the IOVA allocator still returns
0 on failure here...
goto out;
prot = dir2prot(direction);
@@ -2376,7 +2374,7 @@ static dma_addr_t __map_single(struct device *dev,
dma_ops_free_iova(dma_dom, address, pages);
- return AMD_IOMMU_MAPPING_ERROR;
+ return DMA_MAPPING_ERROR;
}
/*
@@ -2427,7 +2425,7 @@ static dma_addr_t map_page(struct device *dev, struct page *page,
if (PTR_ERR(domain) == -EINVAL)
return (dma_addr_t)paddr;
else if (IS_ERR(domain))
- return AMD_IOMMU_MAPPING_ERROR;
+ return DMA_MAPPING_ERROR;
dma_mask = *dev->dma_mask;
dma_dom = to_dma_ops_domain(domain);
@@ -2504,7 +2502,7 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
npages = sg_num_pages(dev, sglist, nelems);
address = dma_ops_alloc_iova(dev, dma_dom, npages, dma_mask);
- if (address == AMD_IOMMU_MAPPING_ERROR)
+ if (address == DMA_MAPPING_ERROR)
..and here.
I very much agree with the concept, but I think the way to go about it
is to convert the implementations which need it to the standardised
*_MAPPING_ERROR value one-by-one, and only then then do the big sweep to
remove them all. That has more of a chance of getting worthwhile review
and testing from the respective relevant parties (I'll confess I came
looking for this bug specifically, since I happened to recall amd_iommu
having a tricky implicit reliance on the old DMA_ERROR_CODE being 0 on x86).
In terms of really minimising the error-checking overhead it's a bit of
a shame that DMA_MAPPING_ERROR = 0 doesn't seem viable as the thing to
standardise on, since that has advantages at the micro-optimisation
level for many ISAs - fixing up the legacy IOMMU code doesn't seem
insurmountable, but I suspect there may well be non-IOMMU platforms
where DMA to physical address 0 is a thing :(
(yeah, I know saving a couple of instructions and potential register
allocations is down in the noise when we're already going from an
indirect call to an inline comparison; I'm mostly just thinking out loud
there)
Robin.
goto out_err;
prot = dir2prot(direction);
@@ -2627,7 +2625,7 @@ static void *alloc_coherent(struct device *dev, size_t size,
*dma_addr = __map_single(dev, dma_dom, page_to_phys(page),
size, DMA_BIDIRECTIONAL, dma_mask);
- if (*dma_addr == AMD_IOMMU_MAPPING_ERROR)
+ if (*dma_addr == DMA_MAPPING_ERROR)
goto out_free;
return page_address(page);
@@ -2678,11 +2676,6 @@ static int amd_iommu_dma_supported(struct device *dev, u64 mask)
return check_device(dev);
}
-static int amd_iommu_mapping_error(struct device *dev, dma_addr_t dma_addr)
-{
- return dma_addr == AMD_IOMMU_MAPPING_ERROR;
-}
-
static const struct dma_map_ops amd_iommu_dma_ops = {
.alloc = alloc_coherent,
.free = free_coherent,
@@ -2691,7 +2684,6 @@ static const struct dma_map_ops amd_iommu_dma_ops = {
.map_sg = map_sg,
.unmap_sg = unmap_sg,
.dma_supported = amd_iommu_dma_supported,
- .mapping_error = amd_iommu_mapping_error,
};
static int init_reserved_iova_ranges(void)
