On 12/30/2022 1:54 PM, Herbert Xu wrote: > 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, Herbert, This patch is no longer relevant to the mainstream kernel. Thanks, Rijo
