From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756838AbeDXL7o (ORCPT ); Tue, 24 Apr 2018 07:59:44 -0400 Received: from mail-lf0-f68.google.com ([209.85.215.68]:40115 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752908AbeDXL7n (ORCPT ); Tue, 24 Apr 2018 07:59:43 -0400 X-Google-Smtp-Source: AIpwx49iO5jGiGGiWobPkvbPXWefT/2PzUdRB2W4CGWM2fRwzrx9ygRix3uWAjQFUkdP2GDgka4jGA== Subject: Re: [Xen-devel] [PATCH 0/1] drm/xen-zcopy: Add Xen zero-copy helper DRM driver To: Wei Liu , jgross@suse.com, Artem Mygaiev , Dongwon Kim , konrad.wilk@oracle.com, airlied@linux.ie, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, "Potrola, MateuszX" , daniel.vetter@intel.com, xen-devel@lists.xenproject.org, boris.ostrovsky@oracle.com, =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: <20180417075928.GT31310@phenom.ffwll.local> <20180417205744.GA15930@downor-Z87X-UD5H> <41487acb-a67a-8933-d0c3-702c19b0938e@gmail.com> <20180418073508.ptvntwedczpvl7bx@MacBook-Pro-de-Roger.local> <20180418101058.hyqk3gr3b2ibxswu@MacBook-Pro-de-Roger.local> <20180420071914.GG31310@phenom.ffwll.local> <76cdc65a-7bb1-9377-7bc5-6164e32f7b5d@gmail.com> <20180423115242.ywdwqblj2aseu3fr@citrix.com> <61105351-8896-072b-abf0-757c7f6c0edf@gmail.com> <20180424115437.GT31310@phenom.ffwll.local> Cc: "Oleksandr_Andrushchenko@epam.com" From: Oleksandr Andrushchenko Message-ID: <18ab5f76-00b0-42a0-fcb8-e0cbf4cdd527@gmail.com> Date: Tue, 24 Apr 2018 14:59:39 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180424115437.GT31310@phenom.ffwll.local> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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