From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v3 1/2] drm/virtio: Add window server support Date: Wed, 7 Feb 2018 03:09:19 +0200 Message-ID: <20180207030636-mutt-send-email-mst__37706.7621717744$1517966170$gmane$org@kernel.org> References: <20180126135803.29781-1-tomeu.vizoso@collabora.com> <20180126135803.29781-2-tomeu.vizoso@collabora.com> <20180201163623.5cs2ysykg5wgulf4@sirius.home.kraxel.org> <49785e0d-936a-c3b4-62dd-aafc7083a942@collabora.com> <20180205122017.4vb5nlpodkq2uhxa@sirius.home.kraxel.org> <20180205160322.sntv5uoqp5o7flnh@sirius.home.kraxel.org> <20180206142302.vdjyqmnoypydci4t@sirius.home.kraxel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20180206142302.vdjyqmnoypydci4t@sirius.home.kraxel.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Gerd Hoffmann Cc: Tomeu Vizoso , David Airlie , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, virtualization@lists.linux-foundation.org, Zach Reizner , kernel@collabora.com List-Id: virtualization@lists.linuxfoundation.org On Tue, Feb 06, 2018 at 03:23:02PM +0100, Gerd Hoffmann wrote: > > Creation of shareable buffer by guest > > ------------------------------------------------- > > > > 1. Client requests virtio driver to create a buffer suitable for sharing > > with host (DRM_VIRTGPU_RESOURCE_CREATE) > > client or guest proxy? > > > 4. QEMU maps that buffer to the guest's address space > > (KVM_SET_USER_MEMORY_REGION), passes the guest PFN to the virtio driver > > That part is problematic. The host can't simply allocate something in > the physical address space, because most physical address space > management is done by the guest. All pci bars are mapped by the guest > firmware for example (or by the guest OS in case of hotplug). > > > 4. QEMU pops data+buffers from the virtqueue, looks up shmem FD for each > > resource, sends data + FDs to the compositor with SCM_RIGHTS If you squint hard, this sounds a bit like a use-case for vhost-user-gpu, does it not? > BTW: Is there a 1:1 relationship between buffers and shmem blocks? Or > does the wayland protocol allow for offsets in buffer meta data, so you > can place multiple buffers in a single shmem block? > > cheers, > Gerd