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Date: Wed, 13 May 2020 10:29:31 +0800 From: Jason Wang <jasowang@...hat.com> To: Jason Gunthorpe <jgg@...lanox.com>, "Raj, Ashok" <ashok.raj@...el.com> Cc: "Tian, Kevin" <kevin.tian@...el.com>, Alex Williamson <alex.williamson@...hat.com>, "Jiang, Dave" <dave.jiang@...el.com>, "vkoul@...nel.org" <vkoul@...nel.org>, "megha.dey@...ux.intel.com" <megha.dey@...ux.intel.com>, "maz@...nel.org" <maz@...nel.org>, "bhelgaas@...gle.com" <bhelgaas@...gle.com>, "rafael@...nel.org" <rafael@...nel.org>, "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>, "tglx@...utronix.de" <tglx@...utronix.de>, "hpa@...or.com" <hpa@...or.com>, "Pan, Jacob jun" <jacob.jun.pan@...el.com>, "Liu, Yi L" <yi.l.liu@...el.com>, "Lu, Baolu" <baolu.lu@...el.com>, "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>, "Luck, Tony" <tony.luck@...el.com>, "Lin, Jing" <jing.lin@...el.com>, "Williams, Dan J" <dan.j.williams@...el.com>, "kwankhede@...dia.com" <kwankhede@...dia.com>, "eric.auger@...hat.com" <eric.auger@...hat.com>, "parav@...lanox.com" <parav@...lanox.com>, "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>, "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>, Paolo Bonzini <pbonzini@...hat.com> Subject: Re: [PATCH RFC 00/15] Add VFIO mediated device support and IMS support for the idxd driver. On 2020/5/9 下午8:21, Jason Gunthorpe wrote: > On Fri, May 08, 2020 at 05:09:09PM -0700, Raj, Ashok wrote: >> Hi Jason >> >> On Fri, May 08, 2020 at 08:16:10PM -0300, Jason Gunthorpe wrote: >>> On Fri, May 08, 2020 at 01:47:10PM -0700, Raj, Ashok wrote: >>> >>>> Even when uaccel was under development, one of the options >>>> was to use VFIO as the transport, goal was the same i.e to keep >>>> the user space have one interface. >>> I feel a bit out of the loop here, uaccel isn't in today's kernel is >>> it? I've heard about it for a while, it sounds very similar to RDMA, >>> so I hope they took some of my advice... >> I think since 5.7 maybe? drivers/misc/uacce. I don't think this is like >> RDMA, its just a plain accelerator. There is no connection management, >> memory registration or other things.. IB was my first job at Intel, >> but saying that i would be giving my age away:) > rdma was the first thing to do kernel bypass, all this stuff is like > rdma at some level.. I see this looks like the 'warp driver' stuff > redone > > Wow, lots wrong here. Oh well. > >>> putting emulation code back into them, except in a more dangerous >>> kernel location. This does not seem like a net win to me. >> Its not a whole lot of emulation right? mdev are soft partitioned. There is >> just a single PF, but we can create a separate partition for the guest using >> PASID along with the normal BDF (RID). And exposing a consistent PCI like >> interface to user space you get everything else for free. >> >> Yes, its not SRIOV, but giving that interface to user space via VFIO, we get >> all of that functionality without having to reinvent a different way to do it. >> >> vDPA went the other way, IRC, they went and put a HW implementation of what >> virtio is in hardware. So they sort of fit the model. Here the instance >> looks and feels like real hardware for the setup and control aspect. > VDPA and this are very similar, of course it depends on the exact HW > implementation. > > Jason Actually this is not a must. Technically we can do ring/descriptor translation in the vDPA driver as what zerocopy AF_XDP did. Thanks >
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