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,
--
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