Re: [PATCH 1/2] dma-mapping: remove ->mapping_error
On Fri, Nov 09, 2018 at 02:41:18PM +, Robin Murphy wrote: >> - >> #define CMD_SET_TYPE(cmd, t) ((cmd)->data[1] |= ((t) << 28)) >> #define LOOP_TIMEOUT 10 >> @@ -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... Indeed. And that shows how the original code was making a mess of these different constants.. > 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). I'll see if I can split this out somehow, but I'm not sure it is going to be all that much more readable.. > 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 :( Yes, that is what I'm more worried about. > (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) The nice bit of standardizing the value is that we get rid of an indirect call, which generally is much more of a problem at the micro-architecture level. ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH 1/2] dma-mapping: remove ->mapping_error
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 10
@@ -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)
___
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https://lists.linuxfoundation.org/mailman/listinfo/iommu
[PATCH 1/2] dma-mapping: remove ->mapping_error
There is no need to perform an indirect function call to check if a
DMA mapping resulted in an error, if we always return the last
possible dma address as the error code. While that could in theory
be a valid DMAable region, it would have to assume we want to
support unaligned DMAs of size 1, which is rather pointless.
Instead simplify the whole machinery by using (~(dma_addr_t)0x0)
as the common error return.
Signed-off-by: Christoph Hellwig
---
arch/alpha/kernel/pci_iommu.c| 10 ++-
arch/arm/common/dmabounce.c | 12 +++--
arch/arm/include/asm/dma-iommu.h | 2 --
arch/arm/mm/dma-mapping.c| 39 +++-
arch/arm64/mm/dma-mapping.c | 15 +++
arch/ia64/hp/common/sba_iommu.c | 8 +-
arch/ia64/sn/pci/pci_dma.c | 8 +-
arch/mips/include/asm/jazzdma.h | 6 -
arch/mips/jazz/jazzdma.c | 16
arch/powerpc/include/asm/iommu.h | 3 ---
arch/powerpc/kernel/dma-iommu.c | 6 -
arch/powerpc/kernel/dma-swiotlb.c| 1 -
arch/powerpc/kernel/iommu.c | 28 ++--
arch/powerpc/platforms/cell/iommu.c | 1 -
arch/powerpc/platforms/pseries/vio.c | 3 +--
arch/s390/pci/pci_dma.c | 18 -
arch/sparc/kernel/iommu.c| 12 +++--
arch/sparc/kernel/iommu_common.h | 2 --
arch/sparc/kernel/pci_sun4v.c| 14 +++---
arch/x86/kernel/amd_gart_64.c| 19 --
arch/x86/kernel/pci-calgary_64.c | 24 ++---
drivers/iommu/amd_iommu.c| 18 -
drivers/iommu/dma-iommu.c| 23 ++--
drivers/iommu/intel-iommu.c | 13 +-
drivers/parisc/ccio-dma.c| 10 +--
drivers/parisc/sba_iommu.c | 10 +--
drivers/pci/controller/vmd.c | 6 -
drivers/xen/swiotlb-xen.c| 12 ++---
include/linux/dma-direct.h | 3 ---
include/linux/dma-iommu.h| 1 -
include/linux/dma-mapping.h | 12 -
kernel/dma/direct.c | 8 +-
kernel/dma/swiotlb.c | 9 +++
33 files changed, 105 insertions(+), 267 deletions(-)
diff --git a/arch/alpha/kernel/pci_iommu.c b/arch/alpha/kernel/pci_iommu.c
index 46e08e0d9181..30339a0369ce 100644
--- a/arch/alpha/kernel/pci_iommu.c
+++ b/arch/alpha/kernel/pci_iommu.c
@@ -291,7 +291,7 @@ pci_map_single_1(struct pci_dev *pdev, void *cpu_addr,
size_t size,
use direct_map above, it now must be considered an error. */
if (! alpha_mv.mv_pci_tbi) {
printk_once(KERN_WARNING "pci_map_single: no HW sg\n");
- return 0;
+ return DMA_MAPPING_ERROR;
}
arena = hose->sg_pci;
@@ -307,7 +307,7 @@ pci_map_single_1(struct pci_dev *pdev, void *cpu_addr,
size_t size,
if (dma_ofs < 0) {
printk(KERN_WARNING "pci_map_single failed: "
"could not allocate dma page tables\n");
- return 0;
+ return DMA_MAPPING_ERROR;
}
paddr &= PAGE_MASK;
@@ -935,11 +935,6 @@ iommu_unbind(struct pci_iommu_arena *arena, long pg_start,
long pg_count)
return 0;
}
-static int alpha_pci_mapping_error(struct device *dev, dma_addr_t dma_addr)
-{
- return dma_addr == 0;
-}
-
const struct dma_map_ops alpha_pci_ops = {
.alloc = alpha_pci_alloc_coherent,
.free = alpha_pci_free_coherent,
@@ -947,7 +942,6 @@ const struct dma_map_ops alpha_pci_ops = {
.unmap_page = alpha_pci_unmap_page,
.map_sg = alpha_pci_map_sg,
.unmap_sg = alpha_pci_unmap_sg,
- .mapping_error = alpha_pci_mapping_error,
.dma_supported = alpha_pci_supported,
};
EXPORT_SYMBOL(alpha_pci_ops);
diff --git a/arch/arm/common/dmabounce.c b/arch/arm/common/dmabounce.c
index 9a92de63426f..5ba4622030ca 100644
--- a/arch/arm/common/dmabounce.c
+++ b/arch/arm/common/dmabounce.c
@@ -257,7 +257,7 @@ static inline dma_addr_t map_single(struct device *dev,
void *ptr, size_t size,
if (buf == NULL) {
dev_err(dev, "%s: unable to map unsafe buffer %p!\n",
__func__, ptr);
- return ARM_MAPPING_ERROR;
+ return DMA_MAPPING_ERROR;
}
dev_dbg(dev, "%s: unsafe buffer %p (dma=%#x) mapped to %p (dma=%#x)\n",
@@ -327,7 +327,7 @@ static dma_addr_t dmabounce_map_page(struct device *dev,
struct page *page,
ret = needs_bounce(dev, dma_addr, size);
if (ret < 0)
- return ARM_MAPPING_ERROR;
+ return DMA_MAPPING_ERROR;
if (ret == 0) {
arm_dma_ops.sync_single_for_device(dev, dma_addr, size, dir);
@@ -336,7 +336,7 @@ static dma_addr_t dmabounce_map_page(struct device *dev,
struct page *page,
if
