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 759A9C433EF for ; Wed, 2 Mar 2022 15:12:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243391AbiCBPNY (ORCPT ); Wed, 2 Mar 2022 10:13:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58318 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234428AbiCBPNX (ORCPT ); Wed, 2 Mar 2022 10:13:23 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1EBB91D0F3 for ; Wed, 2 Mar 2022 07:12:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646233959; 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=6TNiLFlYcGF3ddTJpMJSNjgDj1FGfe5b4PLw2nW6z80=; b=jQx5SxpT5TQyiQro4w3afKwvwxoZT1BFrI7cqo/iNgV73gnyCGtgFpTbb5OQpN6lYLQQJC QwGxftEb5WTB4EyS2JteL24dJl1KtRe/JOHYMlwMDQpPucR0UQZ9oUDHR2I8JQcyAOazqU FnJrs7jYgcREYpM3zS46esj5wlHHAUw= Received: from mail-oo1-f70.google.com (mail-oo1-f70.google.com [209.85.161.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-149-5hmEITpANMee8r3_Nsi2rw-1; Wed, 02 Mar 2022 10:12:38 -0500 X-MC-Unique: 5hmEITpANMee8r3_Nsi2rw-1 Received: by mail-oo1-f70.google.com with SMTP id r4-20020a4abf04000000b0032030c12b39so1412233oop.8 for ; Wed, 02 Mar 2022 07:12:38 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:organization:mime-version:content-transfer-encoding; bh=6TNiLFlYcGF3ddTJpMJSNjgDj1FGfe5b4PLw2nW6z80=; b=z2lKgAj43DSDuUxuPaKmO0kVqai48kLEriMjiAYHasa/QPkHJNKV/QgH8qNRRKEno6 1nTPLnH3OO97MhWrIr5WR42HseIWj2nOkjRlvK9nQZtlba8pw/ro7bM/8HM3ICoBo48y 2ke3ZGbjdfhs06ZyyLxulH+L6ZQQYiP6jMXYh6K/NMRf3VEfFzU97zKIzJmMYOvvfNOG R1iCinR6OQoguGL7S9mFGnW/tBXILXG1M9HBFXqBaG7tepQ84sNCTM/eNRrkYKn4xpH/ EMU3u+w+mg4ass5OdMvbUCPztRBlqnReWo582o+RBI7qBqv3TkWwmlju01D8BxEayaxY XeSg== X-Gm-Message-State: AOAM532Zbueti6Q/Ukej2D/n/xN6/dUCs8HEmliO/6DDc5bmZOGI2Szl aSDXGujbkPSLVLH4rUrXnlQB43zmXo5+CSBOycj2q/KUqBCw0wCF30WI0vujrqOae2olVwrrKXx ZYkNvhsjwo1AG X-Received: by 2002:a05:6830:23b8:b0:5a5:75fd:8f9 with SMTP id m24-20020a05683023b800b005a575fd08f9mr15666160ots.152.1646233957348; Wed, 02 Mar 2022 07:12:37 -0800 (PST) X-Google-Smtp-Source: ABdhPJwUKXcvdMYSNpSDmRV4uh5gtX/gNvk81VHFgaMMwZYft8TCoicAQaumaccPdPuVeKcHQyh9kA== X-Received: by 2002:a05:6830:23b8:b0:5a5:75fd:8f9 with SMTP id m24-20020a05683023b800b005a575fd08f9mr15666135ots.152.1646233957112; Wed, 02 Mar 2022 07:12:37 -0800 (PST) Received: from redhat.com ([38.15.36.239]) by smtp.gmail.com with ESMTPSA id s3-20020a056808208300b002d38ef031d6sm9680263oiw.36.2022.03.02.07.12.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Mar 2022 07:12:36 -0800 (PST) Date: Wed, 2 Mar 2022 08:12:34 -0700 From: Alex Williamson To: Sergio Lopez Cc: qemu-devel@nongnu.org, vgoyal@redhat.com, Fam Zheng , kvm@vger.kernel.org, Jagannathan Raman , Cornelia Huck , Halil Pasic , qemu-block@nongnu.org, Christian Borntraeger , "Michael S. Tsirkin" , David Hildenbrand , Paolo Bonzini , Eric Farman , Hanna Reitz , Stefan Hajnoczi , Elena Ufimtseva , Kevin Wolf , Philippe =?UTF-8?B?TWF0aGlldS1EYXVkw6k=?= , Richard Henderson , qemu-s390x@nongnu.org, Matthew Rosato , John G Johnson , Thomas Huth Subject: Re: [PATCH 1/2] Allow returning EventNotifier's wfd Message-ID: <20220302081234.2378ef33.alex.williamson@redhat.com> In-Reply-To: <20220302113644.43717-2-slp@redhat.com> References: <20220302113644.43717-1-slp@redhat.com> <20220302113644.43717-2-slp@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 Wed, 2 Mar 2022 12:36:43 +0100 Sergio Lopez wrote: > event_notifier_get_fd(const EventNotifier *e) always returns > EventNotifier's read file descriptor (rfd). This is not a problem when > the EventNotifier is backed by a an eventfd, as a single file > descriptor is used both for reading and triggering events (rfd == > wfd). > > But, when EventNotifier is backed by a pipefd, we have two file > descriptors, one that can only be used for reads (rfd), and the other > only for writes (wfd). > > There's, at least, one known situation in which we need to obtain wfd > instead of rfd, which is when setting up the file that's going to be > sent to the peer in vhost's SET_VRING_CALL. > > Extend event_notifier_get_fd() to receive an argument which indicates > whether the caller wants to obtain rfd (false) or wfd (true). There are about 50 places where we add the false arg here and 1 where we use true. Seems it would save a lot of churn to hide this internally, event_notifier_get_fd() returns an rfd, a new event_notifier_get_wfd() returns the wfd. Thanks, Alex