Messages in this thread | | | Date | Sun, 1 Oct 2017 10:04:49 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH v3] dma-debug: fix incorrect pfn calculation |
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On Wed, Sep 27, 2017 at 11:23:52AM +0100, Robin Murphy wrote: > > I found that debug_dma_alloc_coherent() and debug_dma_free_coherent() > > assume that dma_alloc_coherent() always returns a linear address. > > However it's possible that dma_alloc_coherent() returns a non-linear > > address. In this case, page_to_pfn(virt_to_page(virt)) will return an > > incorrect pfn. If the pfn is valid and mapped as a COW page, > > we will hit the warning when doing wp_page_copy().
Hmm, can the debug code assume anything? Right now you're just patching it from supporting linear and vmalloc. But what about other potential mapping types?
> > + entry->pfn = is_vmalloc_addr(virt) ? vmalloc_to_pfn(virt) : > > + page_to_pfn(virt_to_page(virt));
Please use normal if/else conditionsals:
if (is_vmalloc_addr(virt)) entry->pfn = vmalloc_to_pfn(virt); else entry->pfn = page_to_pfn(virt_to_page(virt));
> > + .pfn = is_vmalloc_addr(virt) ? vmalloc_to_pfn(virt) : > > + page_to_pfn(virt_to_page(virt)),
Same here.
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