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Wed, 22 Mar 2023 05:36:21 -0700 (PDT) X-Google-Smtp-Source: AK7set+s1bVDw/httDHazd/bVKfPTyFl2eUE5yP3x7lZIEV1uxid79azuha2BxjfoT9XqWVJ/KVk0w== X-Received: by 2002:a6b:5b15:0:b0:73d:eb4b:345e with SMTP id v21-20020a6b5b15000000b0073deb4b345emr4250309ioh.6.1679488581235; Wed, 22 Mar 2023 05:36:21 -0700 (PDT) Received: from redhat.com ([38.15.36.239]) by smtp.gmail.com with ESMTPSA id f29-20020a02241d000000b003a69bd12c6dsm4820604jaa.58.2023.03.22.05.36.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Mar 2023 05:36:20 -0700 (PDT) Date: Wed, 22 Mar 2023 06:36:14 -0600 From: Alex Williamson To: Jason Gunthorpe Cc: "Tian, Kevin" , "kvm@vger.kernel.org" , "jasowang@redhat.com" , "Hao, Xudong" , "peterx@redhat.com" , "Xu, Terrence" , "chao.p.peng@linux.intel.com" , "linux-s390@vger.kernel.org" , "Liu, Yi L" , "mjrosato@linux.ibm.com" , "lulu@redhat.com" , "joro@8bytes.org" , "nicolinc@nvidia.com" , "Zhao, Yan Y" , "intel-gfx@lists.freedesktop.org" , "eric.auger@redhat.com" , "intel-gvt-dev@lists.freedesktop.org" , "yi.y.sun@linux.intel.com" , "cohuck@redhat.com" , "shameerali.kolothum.thodi@huawei.com" , "suravee.suthikulpanit@amd.com" , "robin.murphy@arm.com" Subject: Re: [PATCH v6 12/24] vfio/pci: Allow passing zero-length fd array in VFIO_DEVICE_PCI_HOT_RESET Message-ID: <20230322063614.571699e4.alex.williamson@redhat.com> In-Reply-To: References: <20230317091557.196638a6.alex.williamson@redhat.com> <20230320165217.5b1019a4.alex.williamson@redhat.com> <20230321143122.632f7e63.alex.williamson@redhat.com> <20230321150112.1c482380.alex.williamson@redhat.com> <20230321164737.62b45132.alex.williamson@redhat.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Wed, 22 Mar 2023 09:27:16 -0300 Jason Gunthorpe wrote: > On Tue, Mar 21, 2023 at 04:47:37PM -0600, Alex Williamson wrote: > > On Tue, 21 Mar 2023 19:20:37 -0300 > > Jason Gunthorpe wrote: > > > > > On Tue, Mar 21, 2023 at 03:01:12PM -0600, Alex Williamson wrote: > > > > > > > > Though it would be nice if qemu didn't need two implementations so Yi > > > > > I'd rather see a new info in this series as well and qemu can just > > > > > consistently use dev_id and never bdf in iommufd mode. > > > > > > > > We also need to consider how libvirt determines if QEMU has the kernel > > > > support it needs to pass file descriptors. It'd be a lot cleaner if > > > > this aligned with the introduction of vfio cdevs. > > > > > > Yes, that would be much better if it was one package. > > > > > > But this is starting to grow and we have so many threads that need to > > > progress blocked on this cdev enablement :( > > > > > > Could we go forward with the cdev main patches and kconfig it to > > > experimental or something while the rest of the parts are completed > > > and tested through qemu? ie move the vfio-pci reset enablment to after > > > the cdev patches? > > > > We need to be able to guarantee that there cannot be any significant > > builds of the kernel with vfio cdev support if our intention is to stage > > it for libvirt. We don't have a global EXPERIMENTAL config option any > > more. Adding new code under BROKEN seems wrong. Fedora ships with > > STAGING enabled. A sternly worded Kconfig entry is toothless. What is > > the proposed mechanism to make this not look like a big uncompiled code > > dump? Thanks, > > I would suggest a sternly worded kconfig and STAGING. > > This isn't such a big issue, we are trying to say that a future > released qemu is not required to work on older kernels with a STAGING > kconfig mark. > > IOW we are saying that qemu release X.0 with production iommufd > requires kernel version > x.y and just lightly reflecting this into > the kconfig. > > qemu should simply not support iommufd if it finds itself on a old > kernel. Inferring features based on kernel versions doesn't work in a world where downstreams backport features to older kernels. Thanks, Alex