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charset=US-ASCII Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Tue, 18 Jul 2023 09:07:09 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-aio@kvack.org, Muchun Song , Tony Krowiak , Matthew Rosato , Paul Durrant , Tom Rix , Jason Wang , Roman Gushchin , dri-devel@lists.freedesktop.org, Michal Hocko , Heiko Carstens , linux-mm@kvack.org, Kirti Wankhede , netdev@vger.kernel.org, Vineeth Vijayan , Diana Craciun , Borislav Petkov , Alexander Gordeev , Fei Li , Xuan Zhuo , Marcin Wojtas , Arnd Bergmann , Leon Romanovsky , Harald Freudenberger , x86@kernel.org, Halil Pasic , Ingo Molnar , Moritz Fischer , Frederic Barrat , Xu Yilun , Christian Borntraeger , linux-fpga@vger.kernel.org, Zhi Wang , Wu Hao , Jason Herne , Eric Farman , Dave Hansen , Andrew Donnellan , Vasily Gorbik , linux-s390@vger.kernel.org, Dominik Behr , intel-gfx@lists.freedesktop.org, Sean Christopherson , Eric Auger , Greg Kroah-Hartman , Shakeel Butt , kvm@vger.kernel.org, Rodrigo Vivi , cgroups@vger.kernel.org, Thomas Gleixner , virtualization@lists.linux-foundation.org, intel-gvt-dev@lists.freedesktop.org, io-uring@vger.kernel.org, Jens Axboe , Tvrtko Ursulin , Christian Brauner , Grzegorz Jaszczyk , Od ed Gabbay , linux-usb@vger.kernel.org, Peter Oberparleiter , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, Benjamin LaHaise , "Michael S. Tsirkin" , Sven Schnelle , Johannes Weiner , linux-fsdevel@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , David Woodhouse , linuxppc-dev@lists.ozlabs.org, Pavel Begunkov Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, 17 Jul 2023 19:12:16 -0300 Jason Gunthorpe wrote: > On Mon, Jul 17, 2023 at 01:08:31PM -0600, Alex Williamson wrote: > > > What would that mechanism be? We've been iterating on getting the > > serialization and buffering correct, but I don't know of another means > > that combines the notification with a value, so we'd likely end up with > > an eventfd only for notification and a separate ring buffer for > > notification values. > > All FDs do this. You just have to make a FD with custom > file_operations that does what this wants. The uAPI shouldn't be able > to tell if the FD is backing it with an eventfd or otherwise. Have the > kernel return the FD instead of accepting it. Follow the basic design > of eg mlx5vf_save_fops Sure, userspace could poll on any fd and read a value from it, but at that point we're essentially duplicating a lot of what eventfd provides for a minor(?) semantic difference over how the counter value is interpreted. Using an actual eventfd allows the ACPI notification to work as just another interrupt index within the existing vfio IRQ uAPI. Thanks, Alex