* [PATCH] arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing
@ 2018-12-10 19:33 Robin Murphy
2018-12-10 19:36 ` Will Deacon
2018-12-12 7:31 ` Chintan Pandya
0 siblings, 2 replies; 5+ messages in thread
From: Robin Murphy @ 2018-12-10 19:33 UTC (permalink / raw)
To: will.deacon, catalin.marinas; +Cc: hch, linux-arm-kernel, m.szyprowski
We need to invalidate the caches *before* clearing the buffer via the
non-cacheable alias, else in the worst case __dma_flush_area() may
write back dirty lines over the top of our nice new zeros.
Fixes: dd65a941f6ba ("arm64: dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
arch/arm64/mm/dma-mapping.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index a3ac26284845..a53704406099 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -429,9 +429,9 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
prot,
__builtin_return_address(0));
if (addr) {
- memset(addr, 0, size);
if (!coherent)
__dma_flush_area(page_to_virt(page), iosize);
+ memset(addr, 0, size);
} else {
iommu_dma_unmap_page(dev, *handle, iosize, 0, attrs);
dma_release_from_contiguous(dev, page,
--
2.19.1.dirty
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing
2018-12-10 19:33 [PATCH] arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing Robin Murphy
@ 2018-12-10 19:36 ` Will Deacon
2018-12-11 11:55 ` Catalin Marinas
2018-12-12 7:31 ` Chintan Pandya
1 sibling, 1 reply; 5+ messages in thread
From: Will Deacon @ 2018-12-10 19:36 UTC (permalink / raw)
To: Robin Murphy; +Cc: catalin.marinas, hch, linux-arm-kernel, m.szyprowski
On Mon, Dec 10, 2018 at 07:33:31PM +0000, Robin Murphy wrote:
> We need to invalidate the caches *before* clearing the buffer via the
> non-cacheable alias, else in the worst case __dma_flush_area() may
> write back dirty lines over the top of our nice new zeros.
>
> Fixes: dd65a941f6ba ("arm64: dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag")
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> arch/arm64/mm/dma-mapping.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index a3ac26284845..a53704406099 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -429,9 +429,9 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
> prot,
> __builtin_return_address(0));
> if (addr) {
> - memset(addr, 0, size);
> if (!coherent)
> __dma_flush_area(page_to_virt(page), iosize);
> + memset(addr, 0, size);
> } else {
> iommu_dma_unmap_page(dev, *handle, iosize, 0, attrs);
> dma_release_from_contiguous(dev, page,
Oh crikey, well spotted!
Acked-by: Will Deacon <will.deacon@arm.com>
Catalin, please take this with a Cc stable.
Will
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing
2018-12-10 19:36 ` Will Deacon
@ 2018-12-11 11:55 ` Catalin Marinas
0 siblings, 0 replies; 5+ messages in thread
From: Catalin Marinas @ 2018-12-11 11:55 UTC (permalink / raw)
To: Will Deacon; +Cc: Robin Murphy, hch, linux-arm-kernel, m.szyprowski
On Mon, Dec 10, 2018 at 07:36:18PM +0000, Will Deacon wrote:
> On Mon, Dec 10, 2018 at 07:33:31PM +0000, Robin Murphy wrote:
> > We need to invalidate the caches *before* clearing the buffer via the
> > non-cacheable alias, else in the worst case __dma_flush_area() may
> > write back dirty lines over the top of our nice new zeros.
> >
> > Fixes: dd65a941f6ba ("arm64: dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag")
> > Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> > ---
> > arch/arm64/mm/dma-mapping.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> > index a3ac26284845..a53704406099 100644
> > --- a/arch/arm64/mm/dma-mapping.c
> > +++ b/arch/arm64/mm/dma-mapping.c
> > @@ -429,9 +429,9 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
> > prot,
> > __builtin_return_address(0));
> > if (addr) {
> > - memset(addr, 0, size);
> > if (!coherent)
> > __dma_flush_area(page_to_virt(page), iosize);
> > + memset(addr, 0, size);
> > } else {
> > iommu_dma_unmap_page(dev, *handle, iosize, 0, attrs);
> > dma_release_from_contiguous(dev, page,
>
> Oh crikey, well spotted!
>
> Acked-by: Will Deacon <will.deacon@arm.com>
>
> Catalin, please take this with a Cc stable.
Queued. Thanks.
--
Catalin
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing
2018-12-10 19:33 [PATCH] arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing Robin Murphy
2018-12-10 19:36 ` Will Deacon
@ 2018-12-12 7:31 ` Chintan Pandya
2018-12-12 7:37 ` Christoph Hellwig
1 sibling, 1 reply; 5+ messages in thread
From: Chintan Pandya @ 2018-12-12 7:31 UTC (permalink / raw)
To: Robin Murphy, will.deacon, catalin.marinas
Cc: hch, linux-arm-kernel, m.szyprowski
On 12/11/2018 1:03 AM, Robin Murphy wrote:
> We need to invalidate the caches *before* clearing the buffer via the
> non-cacheable alias, else in the worst case __dma_flush_area() may
> write back dirty lines over the top of our nice new zeros.
>
> Fixes: dd65a941f6ba ("arm64: dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag")
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> arch/arm64/mm/dma-mapping.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index a3ac26284845..a53704406099 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -429,9 +429,9 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
> prot,
> __builtin_return_address(0));
> if (addr) {
> - memset(addr, 0, size);
> if (!coherent)
> __dma_flush_area(page_to_virt(page), iosize);
> + memset(addr, 0, size);
For coherent case, we still skip flushing/invalidating dirty kernel
mappings. Isn't it a problem ?
Shouldn't it be,
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -774,9 +774,8 @@ static void *__iommu_alloc_attrs(struct device *dev,
size_t size,
prot,
__builtin_return_address(0));
if (addr) {
+ __dma_flush_area(page_to_virt(page), iosize);
memset(addr, 0, size);
- if (!coherent)
- __dma_flush_area(page_to_virt(page),
iosize);
} else {
iommu_dma_unmap_page(dev, *handle, iosize, 0,
attrs);
dma_release_from_contiguous(dev, page,
> } else {
> iommu_dma_unmap_page(dev, *handle, iosize, 0, attrs);
> dma_release_from_contiguous(dev, page,
>
Chintan
--
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Inc. is a member of the Code Aurora Forum, a Linux Foundation
Collaborative Project
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing
2018-12-12 7:31 ` Chintan Pandya
@ 2018-12-12 7:37 ` Christoph Hellwig
0 siblings, 0 replies; 5+ messages in thread
From: Christoph Hellwig @ 2018-12-12 7:37 UTC (permalink / raw)
To: Chintan Pandya
Cc: catalin.marinas, will.deacon, Robin Murphy, hch, linux-arm-kernel,
m.szyprowski
On Wed, Dec 12, 2018 at 01:01:41PM +0530, Chintan Pandya wrote:
>> if (addr) {
>> - memset(addr, 0, size);
>> if (!coherent)
>> __dma_flush_area(page_to_virt(page), iosize);
>> + memset(addr, 0, size);
>
> For coherent case, we still skip flushing/invalidating dirty kernel
> mappings. Isn't it a problem ?
For the dma coherent case there is no need to writeback and/or invalidate
the kernel mapping.
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2018-12-10 19:33 [PATCH] arm64: dma-mapping: Fix FORCE_CONTIGUOUS buffer clearing Robin Murphy
2018-12-10 19:36 ` Will Deacon
2018-12-11 11:55 ` Catalin Marinas
2018-12-12 7:31 ` Chintan Pandya
2018-12-12 7:37 ` Christoph Hellwig
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