Messages in this thread Patch in this message | | | Date | Mon, 21 Nov 2005 17:41:33 +0100 | From | Takashi Iwai <> | Subject | Re: 2.6.15-rc1-mm2 -- Bad page state at free_hot_cold_page (in process 'aplay', page c18eef30) |
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At Mon, 21 Nov 2005 16:25:58 +0000, Russell King wrote: > > On Mon, Nov 21, 2005 at 05:17:12PM +0100, Takashi Iwai wrote: > > Now another question arises: Which is the recommended method for > > mmapping RAM pages, vma nopage callback or remap_pfn_range()? > > > > IIRC, in the ealier versions, the former was recommended because > > remap_page_range() with page-reserve was regarded as a hack. > > But, looking through these changes, I feel that remap_pfn_range() is > > better (easier and stabler) than vma nopage... > > And this brings up the question of this age old patch: > > diff -up -x BitKeeper -x ChangeSet -x SCCS -x _xlk -x '*.orig' -x '*.rej' -r orig/arch/i386/kernel/pci-dma.c linux/arch/i386/kernel/pci-dma.c > --- orig/arch/i386/kernel/pci-dma.c Mon Apr 4 22:52:57 2005 > +++ linux/arch/i386/kernel/pci-dma.c Mon Apr 4 22:44:45 2005 > @@ -50,7 +50,7 @@ void *dma_alloc_coherent(struct device * > ret = (void *)__get_free_pages(gfp, order); > > if (ret != NULL) { > - memset(ret, 0, size); > + memset(ret, 0, PAGE_ALIGN(size)); > *dma_handle = virt_to_phys(ret); > } > return ret; > diff -up -x BitKeeper -x ChangeSet -x SCCS -x _xlk -x '*.orig' -x '*.rej' -r orig/include/asm-i386/dma-mapping.h linux/include/asm-i386/dma-mapping.h > --- orig/include/asm-i386/dma-mapping.h Mon Apr 4 22:54:41 2005 > +++ linux/include/asm-i386/dma-mapping.h Mon Apr 4 22:48:11 2005 > @@ -16,6 +16,23 @@ void *dma_alloc_coherent(struct device * > void dma_free_coherent(struct device *dev, size_t size, > void *vaddr, dma_addr_t dma_handle); > > +static inline int > +dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma, > + void *vaddr, dma_addr_t handle, size_t size) > +{ > + unsigned long offset = vma->vm_pgoff, usize; > + > + size = PAGE_ALIGN(size) >> PAGE_SHIFT; > + usize = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; > + > + if (offset >= size || usize > (size - offset)) > + return -ENXIO; > + > + return remap_page_range(vma, vma->vm_start, > + __pa(vaddr) + (offset << PAGE_SHIFT), > + usize << PAGE_SHIFT, vma->vm_page_prot); > +} > + > static inline dma_addr_t > dma_map_single(struct device *dev, void *ptr, size_t size, > enum dma_data_direction direction) > > which provides the dma mmap API which presently is ARM-only on to x86.
Yes, that's nice. It would be nice if dma_mmap_coherent() is implemented on all architectures.
> Note: the first part of this patch should probably be applied anyway > if you're mmaping dma_alloc_coherent pages to userspace to ensure that > information is not leaked from kernel context.
This reminds me another thing: x86 dma_alloc_coherent() doesn't trim the pages between PAGE_ALIGN(size) and (1 << order). Some archs seem doing this right.
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