On Thu, Mar 30, 2017 at 03:28:21PM -0500, Doug Ledford wrote: > On 3/30/17 9:13 AM, Leon Romanovsky wrote: > > On Thu, Mar 30, 2017 at 02:12:21PM +0300, Marcel Apfelbaum wrote: > > > From: Yuval Shaia <yuval.shaia@xxxxxxxxxx> > > > > > > Hi, > > > > > > General description > > > =================== > > > This is a very early RFC of a new RoCE emulated device > > > that enables guests to use the RDMA stack without having > > > a real hardware in the host. > > > > > > The current implementation supports only VM to VM communication > > > on the same host. > > > Down the road we plan to make possible to be able to support > > > inter-machine communication by utilizing physical RoCE devices > > > or Soft RoCE. > > > > > > The goals are: > > > - Reach fast and secure loos-less Inter-VM data exchange. > > > - Support remote VMs or bare metal machines. > > > - Allow VMs migration. > > > - Do not require to pin all VM memory. > > > > > > > > > Objective > > > ========= > > > Have a QEMU implementation of the PVRDMA device. We aim to do so without > > > any change in the PVRDMA guest driver which is already merged into the > > > upstream kernel. > > > > > > > > > RFC status > > > =========== > > > The project is in early development stages and supports > > > only basic send/receive operations. > > > > > > We present it so we can get feedbacks on design, > > > feature demands and to receive comments from the > > > community pointing us to the "right" direction. > > > > If to judge by the feedback which you got from RDMA community > > for kernel proposal [1], this community failed to understand: > > 1. Why do you need new module? > > In this case, this is a qemu module to allow qemu to provide a virt rdma > device to guests that is compatible with the device provided by VMWare's ESX > product. Right now, the vmware_pvrdma driver works only when the guest is > running on a VMWare ESX server product, this would change that. Marcel > mentioned that they are currently making it compatible because that's the > easiest/quickest thing to do, but in the future they might extend beyond > what VMWare's virt rdma driver provides/uses and might then need to either > modify it to work with their extensions or fork and create their own virt > client driver. Doug, As I mentioned during OFA, I just responded to the latest email, but targeted my questions for their module. Sorry for not being clear about it. > > > 2. Why existing solutions are not enough and can't be extended? > > This patch is against the qemu source code, not the kernel. There is no > other solution in the qemu source code, so there is no existing solution to > extend. > > > 3. Why RXE (SoftRoCE) can't be extended to perform this inter-VM > > communication via virtual NIC? > > Eventually they want this to work on real hardware, and to be more or less > transparent to the guest. They will need to make it independent of the > kernel hardware/driver in use. That means their own virt driver, then the > virt driver will eventually hook into whatever hardware is present on the > system, or failing that, fall back to soft RoCE or soft iWARP if that ever > makes it in the kernel. > > > > > > Can you please help us to fill this knowledge gap? > > > > [1] http://marc.info/?l=linux-rdma&m=149063626907175&w=2 >
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