From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: [RFC PATCH v4 0/3] Add Mediated device support[was: Add vGPU support] Date: Tue, 31 May 2016 08:29:26 -0600 Message-ID: <20160531082926.653ada83@ul30vt.home> References: <1464119897-10844-1-git-send-email-kwankhede@nvidia.com> <20160525074356.52121ab8@ul30vt.home> <20160527085443.27f937eb@t450s.home> <20160528085630.0fb79cc7@ul30vt.home> <7195005e-6461-25fb-9ed9-ec5906b93bec@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: "Ruan, Shuai" , "Tian, Kevin" , "cjia@nvidia.com" , "kvm@vger.kernel.org" , "qemu-devel@nongnu.org" , Kirti Wankhede , "kraxel@redhat.com" , "pbonzini@redhat.com" , "bjsdjshi@linux.vnet.ibm.com" , "Lv, Zhiyuan" To: Jike Song Return-path: In-Reply-To: <7195005e-6461-25fb-9ed9-ec5906b93bec@intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: "Qemu-devel" List-Id: kvm.vger.kernel.org On Tue, 31 May 2016 10:29:10 +0800 Jike Song wrote: > On 05/28/2016 10:56 PM, Alex Williamson wrote: > > On Fri, 27 May 2016 22:43:54 +0000 > > "Tian, Kevin" wrote: > > > >> > >> My impression was that you don't like hypervisor specific thing in VFIO, > >> which makes it a bit tricky to accomplish those tasks in kernel. If we > >> can add Xen specific logic directly in VFIO (like vfio-iommu-xen you > >> mentioned), the whole thing would be easier. > > > > If vfio is hosted in dom0, then Xen is the platform and we need to > > interact with the hypervisor to manage the iommu. That said, there are > > aspects of vfio that do not seem to map well to a hypervisor managed > > iommu or a Xen-like hypervisor. For instance, how does dom0 manage > > iommu groups and what's the distinction of using vfio to manage a > > userspace driver in dom0 versus managing a device for another domain. > > In the case of kvm, vfio has no dependency on kvm, there is some minor > > interaction, but we're not running on kvm and it's not appropriate to > > use vfio as a gateway to interact with a hypervisor that may or may not > > exist. Thanks, > > Hi Alex, > > Beyond iommu, there are other aspects vfio need to interact with Xen? > e.g. to pass-through MMIO, one have to call hypercalls to establish EPT > mappings. If it's part of running on a Xen platform and not trying to interact with a VM in ways that are out of scope for vfio, I might be open to it, I'd need to see a proposal. This also goes back to my question of how does vfio know whether it's configuring a device for a guest driver or a guest VM, with kvm these are one and the same. Thanks, Alex