Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH 0/1] drm/xen-zcopy: Add Xen zero-copy helper DRM driver | From | Oleksandr Andrushchenko <> | Date | Tue, 24 Apr 2018 14:59:39 +0300 |
| |
On 04/24/2018 02:54 PM, Daniel Vetter wrote: > 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): I was lazy to change dumb to dma-buf, so put this notice ;) >> - 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). Of course, please see above > -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@lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/dri-devel
| |