Re: [PATCH v2 1/5] x86: make dma_alloc_coherent() return zeroed memory if CMA is enabled
2014-01-28 Konrad Rzeszutek Wilk konrad.w...@oracle.com: On Mon, Jan 27, 2014 at 02:54:47PM +0100, Marek Szyprowski wrote: Hello, On 2014-01-14 15:13, Akinobu Mita wrote: Calling dma_alloc_coherent() with __GFP_ZERO must return zeroed memory. But when the contiguous memory allocator (CMA) is enabled on x86 and the memory region is allocated by dma_alloc_from_contiguous(), it doesn't return zeroed memory. Because dma_generic_alloc_coherent() forgot to fill the memory region with zero if it was allocated by dma_alloc_from_contiguous() I just wonder how it will work with high mem? I've didn't check the x86 dma mapping code yet, but page_address() works only for pages, which comes from low memory. In other patches you have added an option to place CMA area anywhere in the memory. Is the x86 pci dma code ready for the case when cma area is put into high mem and direct mappings are not available? Yes and no. The swiotbl_bounce does have the code to take that into account. But that is it - nothing else does - so I think you would run in the possiblity of 'page_address' not providing an correct virtual address. Thanks for spotting the issue. I haven't much tested on x86_32. I'll go through it and try to find the solution. Most implementations of dma_alloc_coherent() return zeroed memory regardless of whether __GFP_ZERO is specified. So this fixes it by unconditionally zeroing the allocated memory region. Cc: Marek Szyprowski m.szyprow...@samsung.com Cc: Konrad Rzeszutek Wilk konrad.w...@oracle.com Cc: David Woodhouse dw...@infradead.org Cc: Don Dutile ddut...@redhat.com Cc: Thomas Gleixner t...@linutronix.de Cc: Ingo Molnar mi...@redhat.com Cc: H. Peter Anvin h...@zytor.com Cc: Andi Kleen a...@firstfloor.org Cc: x...@kernel.org Cc: iommu@lists.linux-foundation.org Signed-off-by: Akinobu Mita akinobu.m...@gmail.com --- New patch from this version arch/x86/kernel/pci-dma.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index 872079a..9644405 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -97,7 +97,6 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size, dma_mask = dma_alloc_coherent_mask(dev, flag); -flag |= __GFP_ZERO; again: page = NULL; if (!(flag GFP_ATOMIC)) @@ -118,7 +117,7 @@ again: return NULL; } - +memset(page_address(page), 0, size); *dma_addr = addr; return page_address(page); } Best regards -- Marek Szyprowski, PhD Samsung RD Institute Poland ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v2 1/5] x86: make dma_alloc_coherent() return zeroed memory if CMA is enabled
Hello, On 2014-01-14 15:13, Akinobu Mita wrote: Calling dma_alloc_coherent() with __GFP_ZERO must return zeroed memory. But when the contiguous memory allocator (CMA) is enabled on x86 and the memory region is allocated by dma_alloc_from_contiguous(), it doesn't return zeroed memory. Because dma_generic_alloc_coherent() forgot to fill the memory region with zero if it was allocated by dma_alloc_from_contiguous() I just wonder how it will work with high mem? I've didn't check the x86 dma mapping code yet, but page_address() works only for pages, which comes from low memory. In other patches you have added an option to place CMA area anywhere in the memory. Is the x86 pci dma code ready for the case when cma area is put into high mem and direct mappings are not available? Most implementations of dma_alloc_coherent() return zeroed memory regardless of whether __GFP_ZERO is specified. So this fixes it by unconditionally zeroing the allocated memory region. Cc: Marek Szyprowski m.szyprow...@samsung.com Cc: Konrad Rzeszutek Wilk konrad.w...@oracle.com Cc: David Woodhouse dw...@infradead.org Cc: Don Dutile ddut...@redhat.com Cc: Thomas Gleixner t...@linutronix.de Cc: Ingo Molnar mi...@redhat.com Cc: H. Peter Anvin h...@zytor.com Cc: Andi Kleen a...@firstfloor.org Cc: x...@kernel.org Cc: iommu@lists.linux-foundation.org Signed-off-by: Akinobu Mita akinobu.m...@gmail.com --- New patch from this version arch/x86/kernel/pci-dma.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index 872079a..9644405 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -97,7 +97,6 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size, dma_mask = dma_alloc_coherent_mask(dev, flag); - flag |= __GFP_ZERO; again: page = NULL; if (!(flag GFP_ATOMIC)) @@ -118,7 +117,7 @@ again: return NULL; } - + memset(page_address(page), 0, size); *dma_addr = addr; return page_address(page); } Best regards -- Marek Szyprowski, PhD Samsung RD Institute Poland ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v2 1/5] x86: make dma_alloc_coherent() return zeroed memory if CMA is enabled
2014/1/16 Konrad Rzeszutek Wilk konrad.w...@oracle.com: On Tue, Jan 14, 2014 at 11:13:46PM +0900, Akinobu Mita wrote: Calling dma_alloc_coherent() with __GFP_ZERO must return zeroed memory. But when the contiguous memory allocator (CMA) is enabled on x86 and the memory region is allocated by dma_alloc_from_contiguous(), it doesn't return zeroed memory. Because dma_generic_alloc_coherent() So why not fix it there to return zeroed out memory? I thought it looked nicer than this patch as we can remove memset from all caller of dma_alloc_from_contiguous(). But if I look at the caller on arm, we can't simply remove the memset because __dma_clear_buffer() is used there for ensuring cache flushing and it is used in many places. Of course we can do redundant memset in dma_alloc_from_contiguous(), but now I think this patch is less impact for fixing this problem. ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH v2 1/5] x86: make dma_alloc_coherent() return zeroed memory if CMA is enabled
On Tue, Jan 14, 2014 at 11:13:46PM +0900, Akinobu Mita wrote: Calling dma_alloc_coherent() with __GFP_ZERO must return zeroed memory. But when the contiguous memory allocator (CMA) is enabled on x86 and the memory region is allocated by dma_alloc_from_contiguous(), it doesn't return zeroed memory. Because dma_generic_alloc_coherent() So why not fix it there to return zeroed out memory? forgot to fill the memory region with zero if it was allocated by dma_alloc_from_contiguous() Most implementations of dma_alloc_coherent() return zeroed memory regardless of whether __GFP_ZERO is specified. So this fixes it by unconditionally zeroing the allocated memory region. Cc: Marek Szyprowski m.szyprow...@samsung.com Cc: Konrad Rzeszutek Wilk konrad.w...@oracle.com Cc: David Woodhouse dw...@infradead.org Cc: Don Dutile ddut...@redhat.com Cc: Thomas Gleixner t...@linutronix.de Cc: Ingo Molnar mi...@redhat.com Cc: H. Peter Anvin h...@zytor.com Cc: Andi Kleen a...@firstfloor.org Cc: x...@kernel.org Cc: iommu@lists.linux-foundation.org Signed-off-by: Akinobu Mita akinobu.m...@gmail.com --- New patch from this version arch/x86/kernel/pci-dma.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index 872079a..9644405 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -97,7 +97,6 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size, dma_mask = dma_alloc_coherent_mask(dev, flag); - flag |= __GFP_ZERO; again: page = NULL; if (!(flag GFP_ATOMIC)) @@ -118,7 +117,7 @@ again: return NULL; } - + memset(page_address(page), 0, size); *dma_addr = addr; return page_address(page); } -- 1.8.3.2 ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
[PATCH v2 1/5] x86: make dma_alloc_coherent() return zeroed memory if CMA is enabled
Calling dma_alloc_coherent() with __GFP_ZERO must return zeroed memory. But when the contiguous memory allocator (CMA) is enabled on x86 and the memory region is allocated by dma_alloc_from_contiguous(), it doesn't return zeroed memory. Because dma_generic_alloc_coherent() forgot to fill the memory region with zero if it was allocated by dma_alloc_from_contiguous() Most implementations of dma_alloc_coherent() return zeroed memory regardless of whether __GFP_ZERO is specified. So this fixes it by unconditionally zeroing the allocated memory region. Cc: Marek Szyprowski m.szyprow...@samsung.com Cc: Konrad Rzeszutek Wilk konrad.w...@oracle.com Cc: David Woodhouse dw...@infradead.org Cc: Don Dutile ddut...@redhat.com Cc: Thomas Gleixner t...@linutronix.de Cc: Ingo Molnar mi...@redhat.com Cc: H. Peter Anvin h...@zytor.com Cc: Andi Kleen a...@firstfloor.org Cc: x...@kernel.org Cc: iommu@lists.linux-foundation.org Signed-off-by: Akinobu Mita akinobu.m...@gmail.com --- New patch from this version arch/x86/kernel/pci-dma.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index 872079a..9644405 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -97,7 +97,6 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size, dma_mask = dma_alloc_coherent_mask(dev, flag); - flag |= __GFP_ZERO; again: page = NULL; if (!(flag GFP_ATOMIC)) @@ -118,7 +117,7 @@ again: return NULL; } - + memset(page_address(page), 0, size); *dma_addr = addr; return page_address(page); } -- 1.8.3.2 ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
