On Mon, Dec 14, 2015 at 02:00:05PM +0000, David Vrabel wrote: > On 07/12/15 16:19, Stefano Stabellini wrote: > > Hi all, > > > > this patch series introduces support for running Linux on top of Xen > > inside a virtual machine with virtio devices (nested virt scenario). > > The problem is that Linux virtio drivers use virt_to_phys to get the > > guest pseudo-physical addresses to pass to the backend, which doesn't > > work as expected on Xen. > > > > Switching the virtio drivers to the dma APIs (dma_alloc_coherent, > > dma_map/unmap_single and dma_map/unmap_sg) would solve the problem, as > > Xen support in Linux provides an implementation of the dma API which > > takes care of the additional address conversions. However using the dma > > API would increase the complexity of the non-Xen case too. We would also > > need to keep track of the physical or virtual address in addition to the > > dma address for each vring_desc to be able to free the memory in > > detach_buf (see patch #3). > > > > Instead this series adds few obvious checks to perform address > > translations in a couple of key places, without changing non-Xen code > > paths. You are welcome to suggest improvements or alternative > > implementations. > > Andy Lutomirski also looked at this. Andy what happened to this work? > > David The approach there was to try and convert all virtio to use DMA API unconditionally. This is reasonable if there's a way for devices to request 1:1 mappings individually. As that is currently missing, that patchset can not be merged yet. -- MST _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
