From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <1673524110.7417235-2-xuanzhuo@linux.alibaba.com> Subject: Re: [virtio-dev] [PATCH v2 1/1] virtio-ism: introduce new device virtio-ism Date: Thu, 12 Jan 2023 19:48:30 +0800 From: Xuan Zhuo References: <20221223081354.15026-1-xuanzhuo@linux.alibaba.com> <20221223081354.15026-2-xuanzhuo@linux.alibaba.com> <20230110233401.131cc97a.pasic@linux.ibm.com> <1673435333.1297436-1-xuanzhuo@linux.alibaba.com> <20230111161128.48e6d7e0.pasic@linux.ibm.com> <20230112014722-mutt-send-email-mst@kernel.org> <87zgaocffm.fsf@redhat.com> In-Reply-To: <87zgaocffm.fsf@redhat.com> Content-Type: text/plain; charset="US-ASCII"; x-default=true To: Cornelia Huck Cc: Halil Pasic , virtio-dev@lists.oasis-open.org, hans@linux.alibaba.com, herongguang@linux.alibaba.com, zmlcc@linux.alibaba.com, dust.li@linux.alibaba.com, tonylu@linux.alibaba.com, zhenzao@linux.alibaba.com, helinguo@linux.alibaba.com, gerry@linux.alibaba.com, Jan Kiszka , wintera@linux.ibm.com, kgraul@linux.ibm.com, wenjia@linux.ibm.com, jaka@linux.ibm.com, hca@linux.ibm.com, twinkler@linux.ibm.com, raspl@linux.ibm.com, "Michael S. Tsirkin" , Jason Wang List-ID: On Thu, 12 Jan 2023 09:42:05 +0100, Cornelia Huck wrote: > On Thu, Jan 12 2023, "Michael S. Tsirkin" wrote: > > > On Thu, Jan 12, 2023 at 10:01:25AM +0800, Jason Wang wrote: > >> On Wed, Jan 11, 2023 at 11:11 PM Halil Pasic wrote: > >> > > >> > On Wed, 11 Jan 2023 19:08:53 +0800 > >> > Xuan Zhuo wrote: > >> > > >> > > > > +ISM(Internal Shared Memory) device provides the ability to share memory between > >> > > > > +different VMs launched from the same entity. > >> > > > > >> > > > Launched by instead of from? Maybe introduce a catchy name for the > >> > > > "entity that launched the VMs" and prevent oversimplification by > >> > > > explaining any shortcomings of the name if any in one place. Host would > >> > > > be one candidate, VMM another. > >> > > > >> > > Cornelia Huck wrote: > >> > > > >> > > Is there a way to avoid the term "host" (throughout this document)? > >> > > IIUC, you need the uniqueness within the scope of the entity that > >> > > launches the different instances that get shared access to the regions > >> > > (which could conceivably a unit of hardware?) > >> > > > >> > > And I think she is right, so I am trying to remove the term HOST. > >> > > > >> > > Do you have better opinions? I think VMM is not particularly suitable. > > > > I think fundamentally from spec POV memory is shared between devices. > > How sharing is accomplished guest does not care so neither should the > > spec. Can some RDMA tricks be used for synchronisation behind the > > scenes? Maybe, the spec does not care. But we can give an example. > > > > So something like: > > > > An ISM(Internal Shared Memory) device provides the ability to > > access memory shared between multiple devices. This allows low-overhead > > communication in presence of such memory. For example, memory can be > > shared with guests of multiple virtual machines running on the same > > host, with each virtual machine including an ISM device and with > > the guests using the ISM devices to access the shared memory. > > > > what do others think? > > I like that: we don't want to talk about hosts/VMMs/etc. as we > fundamentally deal with devices and drivers, but sharing between guests > is of course the obvious use case. > > I'm just wondering how best to express the uniqueness scope, is it per > (ISM) device? No, each vm has at least one separate device. The devices in a host form an uniqueness scope. Thanks.