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 | Mon, 23 Apr 2018 15:10:35 +0300 |
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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
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
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