From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A6B4C001B0 for ; Mon, 17 Jul 2023 22:53:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230195AbjGQWxl (ORCPT ); Mon, 17 Jul 2023 18:53:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229449AbjGQWxj (ORCPT ); Mon, 17 Jul 2023 18:53:39 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E82F13E for ; Mon, 17 Jul 2023 15:52:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689634329; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8wy84DSSq8n2YYiK0mWellsvoswCFp/2kMAmdZ+UHHc=; b=WSU35uqKWX5qXsL9Eqi4qqS9SCAvtRdUoP1pqlX2O/1cZK2gLwhVZqB5eExNH9bGJCaIvz BDObKB9Pjgy9nnNWI0Mg64rgQFu1m48ni/wL21sFRtdMbxZw6ZsGTbH7RccOeY6fV1KDLB hn5FNoggx6POG5Pi2hj0zNHisqxMXTQ= Received: from mail-il1-f197.google.com (mail-il1-f197.google.com [209.85.166.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-155-S-ZFKSNDOkq59YpC1ijFFA-1; Mon, 17 Jul 2023 18:52:07 -0400 X-MC-Unique: S-ZFKSNDOkq59YpC1ijFFA-1 Received: by mail-il1-f197.google.com with SMTP id e9e14a558f8ab-3476c6ad2ddso34866025ab.3 for ; Mon, 17 Jul 2023 15:52:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689634327; x=1692226327; h=content-transfer-encoding:mime-version:organization:references :in-reply-to:message-id:subject:cc:to:from:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=8wy84DSSq8n2YYiK0mWellsvoswCFp/2kMAmdZ+UHHc=; b=LKObbZmGD9jNOkt546fL0FpPemvN9GFhbKl65ABjnXJXw/4yNtUQugVLbQ8g9kbQ41 vWQi6kyC5n6iYzywsbSmomGK+tDiNEb9kC2ClaJR0o7ak7PZjPWWFSIv9rS4HxaVoXiT 2boMLPes4tYm35Bmww7u9lhYtc8iBQgxCskJrp/MCHnEo65guRNeTkgG8L0sWXfbq4WO HUSjrEFkbj/W+4s0Yv05IvUDbAU4EjOsLo634P70qXBMOoHGypMfvnqIgORgUh+iQ4bZ E38LazN34DgvlAaPHqTQne1X6QDduRmVIrIp88FjXdp7Kfr0wNLB6Ioh2t3pyeFDP0MK +fhw== X-Gm-Message-State: ABy/qLa7dElPsDkp+jOZtmcINnVuCZ3ojTS0DX+sFMpm6/jwRKm5ciuC x5oXMKA2kEhaCDM9SAtgl13IKp7cyXRtXGw7hMo735ToDH3yY7OzqS9JHL4U0afxDUZq4XUme83 CtpvgifyWwIOJ X-Received: by 2002:a92:c651:0:b0:347:693a:7300 with SMTP id 17-20020a92c651000000b00347693a7300mr1012024ill.26.1689634327046; Mon, 17 Jul 2023 15:52:07 -0700 (PDT) X-Google-Smtp-Source: APBJJlGlBYmCdY1EaUds5QDcX7E6PqePOm9wJTOwk2wgOBkeJp+9wxIVvWJlHjSTuTXhWw/m+atXtQ== X-Received: by 2002:a92:c651:0:b0:347:693a:7300 with SMTP id 17-20020a92c651000000b00347693a7300mr1012015ill.26.1689634326829; Mon, 17 Jul 2023 15:52:06 -0700 (PDT) Received: from redhat.com ([38.15.36.239]) by smtp.gmail.com with ESMTPSA id d10-20020a92ddca000000b00341c0710169sm242627ilr.46.2023.07.17.15.52.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Jul 2023 15:52:06 -0700 (PDT) Date: Mon, 17 Jul 2023 16:52:03 -0600 From: Alex Williamson To: Jason Gunthorpe Cc: Grzegorz Jaszczyk , Christian Brauner , linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-usb@vger.kernel.org, Matthew Rosato , Paul Durrant , Tom Rix , Jason Wang , dri-devel@lists.freedesktop.org, Michal Hocko , linux-mm@kvack.org, Kirti Wankhede , Paolo Bonzini , Jens Axboe , Vineeth Vijayan , Diana Craciun , Alexander Gordeev , Xuan Zhuo , Shakeel Butt , Vasily Gorbik , Leon Romanovsky , Harald Freudenberger , Fei Li , x86@kernel.org, Roman Gushchin , Halil Pasic , Ingo Molnar , intel-gfx@lists.freedesktop.org, Christian Borntraeger , linux-fpga@vger.kernel.org, Zhi Wang , Wu Hao , Jason Herne , Eric Farman , Dave Hansen , Andrew Donnellan , Arnd Bergmann , linux-s390@vger.kernel.org, Heiko Carstens , Johannes Weiner , linuxppc-dev@lists.ozlabs.org, Eric Auger , Borislav Petkov , 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, netdev@vger.kernel.org, Tony Krowiak , Tvrtko Ursulin , Pavel Begunkov , Sean Christopherson , Oded Gabbay , Muchun Song , Peter Oberparleiter , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, Benjamin LaHaise , "Michael S. Tsirkin" , Sven Schnelle , Greg Kroah-Hartman , Frederic Barrat , Moritz Fischer , Vitaly Kuznetsov , David Woodhouse , Xu Yilun , Dominik Behr , Marcin Wojtas Subject: Re: [PATCH 0/2] eventfd: simplify signal helpers Message-ID: <20230717165203.4ee6b1e6.alex.williamson@redhat.com> In-Reply-To: References: <20230630155936.3015595-1-jaz@semihalf.com> <20230714-gauner-unsolidarisch-fc51f96c61e8@brauner> <20230717130831.0f18381a.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: kvm@vger.kernel.org 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