On Fri, Dec 23, 2022 at 05:45:24PM +0530, Rijo Thomas wrote: > > > dma_alloc_coherent memory is just as contiguous as __get_free_pages, and > > calling dma_alloc_coherent from a guest does not guarantee that the memory is > > contiguous in host memory either. The memory would look contiguous from the > > device point of view thanks to the IOMMU though (in both cases). So this is not > > about being contiguous but other properties that you might rely on (dma mask > > most likely, or coherent if you're not running this on x86?). > > > > Can you confirm why this fixes things and update the comment to reflect that. > > I see what you are saying. > > We verified this in Xen Dom0 PV guest, where dma_alloc_coherent() returned a memory > that is contiguous in machine address space, and the machine address was returned > in the dma handle (buf->dma). So is this even relevant to the mainstream kernel or is this patch only needed for Xen Dom0? Thanks, -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
