On Mon, Apr 23, 2018 at 03:10:35PM +0300, Oleksandr Andrushchenko wrote: > On 04/23/2018 02:52 PM, Wei Liu wrote: > > On Fri, Apr 20, 2018 at 02:25:20PM +0300, Oleksandr Andrushchenko wrote: > > > > > the gntdev. > > > > > > > > > > I think this is generic enough that it could be implemented by a > > > > > device not tied to Xen. AFAICT the hyper_dma guys also wanted > > > > > something similar to this. > > > > You can't just wrap random userspace memory into a dma-buf. We've just had > > > > this discussion with kvm/qemu folks, who proposed just that, and after a > > > > bit of discussion they'll now try to have a driver which just wraps a > > > > memfd into a dma-buf. > > > So, we have to decide either we introduce a new driver > > > (say, under drivers/xen/xen-dma-buf) or extend the existing > > > gntdev/balloon to support dma-buf use-cases. > > > > > > Can anybody from Xen community express their preference here? > > > > > Oleksandr talked to me on IRC about this, he said a few IOCTLs need to > > be added to either existing drivers or a new driver. > > > > I went through this thread twice and skimmed through the relevant > > documents, but I couldn't see any obvious pros and cons for either > > approach. So I don't really have an opinion on this. > > > > But, assuming if implemented in existing drivers, those IOCTLs need to > > be added to different drivers, which means userspace program needs to > > write more code and get more handles, it would be slightly better to > > implement a new driver from that perspective. > If gntdev/balloon extension is still considered: > > All the IOCTLs will be in gntdev driver (in current xen-zcopy terminology): > - DRM_ICOTL_XEN_ZCOPY_DUMB_FROM_REFS > - DRM_IOCTL_XEN_ZCOPY_DUMB_TO_REFS > - DRM_IOCTL_XEN_ZCOPY_DUMB_WAIT_FREE s/DUMB/DMA_BUF/ please. This is generic dma-buf, it has nothing to do with the dumb scanout buffer support in the drm/gfx subsystem. This here can be used for any zcopy sharing among guests (as long as your endpoints understands dma-buf, which most relevant drivers do). -Daniel > > Balloon driver extension, which is needed for contiguous/DMA > buffers, will be to provide new *kernel API*, no UAPI is needed. > > > Wei. > Thank you, > Oleksandr > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
