Re: [PATCH v1 14/16] x86/amd_gart: return error code from gart_map_sg()

[Robin Murphy]

On 2021-07-16 07:32, Christoph Hellwig wrote:

On Thu, Jul 15, 2021 at 10:45:42AM -0600, Logan Gunthorpe wrote:

@@ -458,7 +460,7 @@ static int gart_map_sg(struct device *dev, struct 
scatterlist *sg, int nents,
iommu_full(dev, pages << PAGE_SHIFT, dir);
for_each_sg(sg, s, nents, i)
s->dma_address = DMA_MAPPING_ERROR;
-   return 0;
+   return ret;


While we're at it - setting the ->dma_address to DMA_MAPPING_ERROR is
not part of the ->map_sg calling convention.  Might be worth to fix
up while we're at it.


Especially since it's not even zeroing dma_length, which at least is a 
documented indicator of validity (even if it's not strictly defined for 
failure cases either).


Robin.

Re: [PATCH v1 14/16] x86/amd_gart: return error code from gart_map_sg()

[Christoph Hellwig]

On Thu, Jul 15, 2021 at 10:45:42AM -0600, Logan Gunthorpe wrote:
> @@ -458,7 +460,7 @@ static int gart_map_sg(struct device *dev, struct 
> scatterlist *sg, int nents,
>   iommu_full(dev, pages << PAGE_SHIFT, dir);
>   for_each_sg(sg, s, nents, i)
>   s->dma_address = DMA_MAPPING_ERROR;
> - return 0;
> + return ret;

While we're at it - setting the ->dma_address to DMA_MAPPING_ERROR is
not part of the ->map_sg calling convention.  Might be worth to fix
up while we're at it.

[PATCH v1 14/16] x86/amd_gart: return error code from gart_map_sg()

[Logan Gunthorpe]

From: Martin Oliveira 

The .map_sg() op now expects an error code instead of zero on failure.

So make __dma_map_cont() return a valid errno (which is then propagated
to gart_map_sg() via dma_map_cont()) and return it in case of failure.

Also, return -EINVAL in case of invalid nents.

Signed-off-by: Martin Oliveira 
Signed-off-by: Logan Gunthorpe 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: Niklas Schnelle 
Cc: Thomas Bogendoerfer 
Cc: Michael Ellerman 
---
 arch/x86/kernel/amd_gart_64.c | 16 +---
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
index 9ac696487b13..46aea9a4f26b 100644
--- a/arch/x86/kernel/amd_gart_64.c
+++ b/arch/x86/kernel/amd_gart_64.c
@@ -331,7 +331,7 @@ static int __dma_map_cont(struct device *dev, struct 
scatterlist *start,
int i;
 
if (iommu_start == -1)
-   return -1;
+   return -ENOMEM;
 
for_each_sg(start, s, nelems, i) {
unsigned long pages, addr;
@@ -380,13 +380,13 @@ static int gart_map_sg(struct device *dev, struct 
scatterlist *sg, int nents,
   enum dma_data_direction dir, unsigned long attrs)
 {
struct scatterlist *s, *ps, *start_sg, *sgmap;
-   int need = 0, nextneed, i, out, start;
+   int need = 0, nextneed, i, out, start, ret;
unsigned long pages = 0;
unsigned int seg_size;
unsigned int max_seg_size;
 
if (nents == 0)
-   return 0;
+   return -EINVAL;
 
out = 0;
start   = 0;
@@ -414,8 +414,9 @@ static int gart_map_sg(struct device *dev, struct 
scatterlist *sg, int nents,
if (!iommu_merge || !nextneed || !need || s->offset ||
(s->length + seg_size > max_seg_size) ||
(ps->offset + ps->length) % PAGE_SIZE) {
-   if (dma_map_cont(dev, start_sg, i - start,
-sgmap, pages, need) < 0)
+   ret = dma_map_cont(dev, start_sg, i - start,
+  sgmap, pages, need);
+   if (ret < 0)
goto error;
out++;
 
@@ -432,7 +433,8 @@ static int gart_map_sg(struct device *dev, struct 
scatterlist *sg, int nents,
pages += iommu_num_pages(s->offset, s->length, PAGE_SIZE);
ps = s;
}
-   if (dma_map_cont(dev, start_sg, i - start, sgmap, pages, need) < 0)
+   ret = dma_map_cont(dev, start_sg, i - start, sgmap, pages, need);
+   if (ret < 0)
goto error;
out++;
flush_gart();
@@ -458,7 +460,7 @@ static int gart_map_sg(struct device *dev, struct 
scatterlist *sg, int nents,
iommu_full(dev, pages << PAGE_SHIFT, dir);
for_each_sg(sg, s, nents, i)
s->dma_address = DMA_MAPPING_ERROR;
-   return 0;
+   return ret;
 }
 
 /* allocate and map a coherent mapping */
-- 
2.20.1