Messages in this thread | | | Date | Wed, 27 Apr 2005 19:55:38 +0100 | From | Russell King <> | Subject | Re: returning non-ram via ->nopage, was Re: [patch] mspec driver for 2.6.12-rc2-mm3 |
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On Wed, Apr 27, 2005 at 02:03:50PM -0400, Jes Sorensen wrote: > >>>>> "Christoph" == Christoph Hellwig <hch@infradead.org> writes: > > Christoph> On Wed, Apr 27, 2005 at 11:53:15AM -0400, Jeff Garzik > Christoph> wrote: > >> I don't see anything wrong with a ->nopage approach. > >> > >> At Linus's suggestion, I used ->nopage in the implementation of > >> sound/oss/via82cxxx_audio.c. > > Christoph> The difference is that you return kernel memory (actually > Christoph> pci_alloc_consistant memory that has it's own set of > Christoph> problems), while this is memory not in mem_map, so he > Christoph> allocates some regularly kernel memory too to have a struct > Christoph> page and just leaks it > > Are you suggesting then that we change do_no_page to handle this as a > special return value then?
If you're looking to mmap dma memory, ARM already supports the API which was discussed (although not properly imho) on linux-arch. I previously posted a potential patch for x86, but it has the problem that remap_pfn_range() will not work on such memory because it isn't marked reserved.
In addition, if you're mmaping dma memory on x86 as is, you're providing a potential security hole - the x86 DMA memory allocator does not extend its zeroing to cover the entire last page of the allocation.
-- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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