From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neo Jia Subject: Re: [PATCH 0/2] KVM: MMU: support VMAs that got remap_pfn_range-ed Date: Tue, 5 Jul 2016 19:57:50 -0700 Message-ID: <20160706025750.GA9457@nvidia.com> References: <1467291711-3230-1-git-send-email-pbonzini@redhat.com> <20160705054147.GA27138@nvidia.com> <577C664E.3080802@linux.intel.com> <20160706021839.GA9064@nvidia.com> <577C6E66.60601@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Paolo Bonzini , , , Kirti Wankhede , Andrea Arcangeli , Radim =?utf-8?B?S3LEjW3DocWZ?= To: Xiao Guangrong Return-path: Content-Disposition: inline In-Reply-To: <577C6E66.60601@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Wed, Jul 06, 2016 at 10:35:18AM +0800, Xiao Guangrong wrote: >=20 >=20 > On 07/06/2016 10:18 AM, Neo Jia wrote: > >On Wed, Jul 06, 2016 at 10:00:46AM +0800, Xiao Guangrong wrote: > >> > >> > >>On 07/05/2016 08:18 PM, Paolo Bonzini wrote: > >>> > >>> > >>>On 05/07/2016 07:41, Neo Jia wrote: > >>>>On Thu, Jun 30, 2016 at 03:01:49PM +0200, Paolo Bonzini wrote: > >>>>>The vGPU folks would like to trap the first access to a BAR by s= etting > >>>>>vm_ops on the VMAs produced by mmap-ing a VFIO device. The faul= t handler > >>>>>then can use remap_pfn_range to place some non-reserved pages in= the VMA. > >>>>> > >>>>>KVM lacks support for this kind of non-linear VM_PFNMAP mapping,= and these > >>>>>patches should fix this. > >>>> > >>>>Hi Paolo, > >>>> > >>>>I have tested your patches with the mediated passthru patchset th= at is being > >>>>reviewed in KVM and QEMU mailing list. > >>>> > >>>>The fault handler gets called successfully and the previously map= ped memory gets > >>>>unmmaped correctly via unmap_mapping_range. > >>> > >>>Great, then I'll include them in 4.8. > >> > >>Code is okay, but i still suspect if this implementation, fetch mmi= o pages in fault > >>handler, is needed. We'd better include these patches after the des= ign of vfio > >>framework is decided. > > > >Hi Guangrong, > > > >I disagree. The design of VFIO framework has been actively discussed= in the KVM > >and QEMU mailing for a while and the fault handler is agreed upon to= provide the > >flexibility for different driver vendors' implementation. With that = said, I am > >still open to discuss with you and anybody else about this framework= as the goal > >is to allow multiple vendor to plugin into this framework to support= their > >mediated device virtualization scheme, such as Intel, IBM and us. >=20 > The discussion is still going on. And current vfio patchset we review= ed is still > problematic. My point is the fault handler part has been discussed already, with tha= t said I am always open to any constructive suggestions to make things better an= d maintainable. (Appreciate your code review on the VFIO thread, I think = we still own you another response, will do that.) >=20 > > > >May I ask you what the exact issue you have with this interface for = Intel to support > >your own GPU virtualization? >=20 > Intel's vGPU can work with this framework. We really appreciate your = / nvidia's > contribution. Then, I don't think we should embargo Paolo's patch. >=20 > i didn=E2=80=99t mean to offend you, i just want to make sure if this= complexity is really > needed and inspect if this framework is safe enough and think it over= if we have > a better implementation. Not at all. :-) Suggestions are always welcome, I just want to know the exact issues yo= u have with the code so I can have a better response to address that with prop= er=20 information. Thanks, Neo