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Tsirkin" To: Jason Gunthorpe Cc: Yishai Hadas , alex.williamson@redhat.com, jasowang@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, parav@nvidia.com, feliu@nvidia.com, jiri@nvidia.com, kevin.tian@intel.com, joao.m.martins@oracle.com, leonro@nvidia.com, maorg@nvidia.com Subject: Re: [PATCH vfio 11/11] vfio/virtio: Introduce a vfio driver over virtio devices Message-ID: <20230921124331-mutt-send-email-mst@kernel.org> References: <20230921124040.145386-1-yishaih@nvidia.com> <20230921124040.145386-12-yishaih@nvidia.com> <20230921090844-mutt-send-email-mst@kernel.org> <20230921141125.GM13733@nvidia.com> <20230921101509-mutt-send-email-mst@kernel.org> <20230921164139.GP13733@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230921164139.GP13733@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Sep 21, 2023 at 01:41:39PM -0300, Jason Gunthorpe wrote: > On Thu, Sep 21, 2023 at 10:16:04AM -0400, Michael S. Tsirkin wrote: > > On Thu, Sep 21, 2023 at 11:11:25AM -0300, Jason Gunthorpe wrote: > > > On Thu, Sep 21, 2023 at 09:16:21AM -0400, Michael S. Tsirkin wrote: > > > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > > > index bf0f54c24f81..5098418c8389 100644 > > > > > --- a/MAINTAINERS > > > > > +++ b/MAINTAINERS > > > > > @@ -22624,6 +22624,12 @@ L: kvm@vger.kernel.org > > > > > S: Maintained > > > > > F: drivers/vfio/pci/mlx5/ > > > > > > > > > > +VFIO VIRTIO PCI DRIVER > > > > > +M: Yishai Hadas > > > > > +L: kvm@vger.kernel.org > > > > > +S: Maintained > > > > > +F: drivers/vfio/pci/virtio > > > > > + > > > > > VFIO PCI DEVICE SPECIFIC DRIVERS > > > > > R: Jason Gunthorpe > > > > > R: Yishai Hadas > > > > > > > > Tying two subsystems together like this is going to cause pain when > > > > merging. God forbid there's something e.g. virtio net specific > > > > (and there's going to be for sure) - now we are talking 3 > > > > subsystems. > > > > > > Cross subsystem stuff is normal in the kernel. > > > > Yea. But it's completely spurious here - virtio has its own way > > to work with userspace which is vdpa and let's just use that. > > Keeps things nice and contained. > > vdpa is not vfio, I don't know how you can suggest vdpa is a > replacement for a vfio driver. They are completely different > things. > Each side has its own strengths, and vfio especially is accelerating > in its capability in way that vpda is not. eg if an iommufd conversion > had been done by now for vdpa I might be more sympathetic. Yea, I agree iommufd is a big problem with vdpa right now. Cindy was sick and I didn't know and kept assuming she's working on this. I don't think it's a huge amount of work though. I'll take a look. Is there anything else though? Do tell. > Asking for > someone else to do a huge amount of pointless work to improve vdpa > just to level of this vfio driver already is at is ridiculous. > > vdpa is great for certain kinds of HW, let it focus on that, don't try > to paint it as an alternative to vfio. It isn't. > > Jason There are a bunch of things that I think are important for virtio that are completely out of scope for vfio, such as migrating cross-vendor. What is the huge amount of work am I asking to do? -- MST