Messages in this thread |  | | Subject | Re: [PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING | From | Walter Wu <> | Date | Tue, 2 Nov 2021 15:26:12 +0800 |
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Hi Christoph,
I am sorry, fix my typo.
Walter
On Tue, 2021-11-02 at 07:41 +0100, Christoph Hellwig wrote: > As others pointed out, DMA_ATTR_NO_KERNEL_MAPPING just means the > caller can't rely on a kernel mapping. So the "fix" here is > wrong. That being said for cases where we can easily remove a page > from the kernel mapping it would be nice to do to: > > a) improve security > b) as a debug check to see that no one actually tries to access it > > > + /* remove kernel mapping for pages */ > > + set_memory_valid((unsigned > > long)phys_to_virt(dma_to_phys(dev, *dma_handle)), > > Please avoid overly long lines. Also this function only exists for > arm64 > also and others pointed out won't work for all cases.
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