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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id ECCD1EE57EB for ; Fri, 8 Sep 2023 10:47:22 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qeZ0F-0001JR-K9; Fri, 08 Sep 2023 06:46:20 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qeZ08-0001I1-CT for qemu-devel@nongnu.org; Fri, 08 Sep 2023 06:46:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qeZ04-0004Bk-Mt for qemu-devel@nongnu.org; Fri, 08 Sep 2023 06:46:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1694169967; 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: in-reply-to:in-reply-to:references:references; bh=zKWkZ2mg4fWzQS8Vnd6rLphnHNc7+O3C5Efy8HMutw0=; b=MIqUzaQT/CCSzTIHhE3J/P3AXmHrjHOF+stYJaLAMQlMFktGW15seilDW9Ndq69FoK0Ply r0/P6NFRKMfUDAhSv3C18hSC4t0N4LPsksKPavfAJD5Ftktnx9tLXL45uvVxp9cLuKo0AS rS2axYpRW/m3TRmGCGbJVlSDUeOMjus= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-563-Tf0999twN-mjlLwjFk9DVQ-1; Fri, 08 Sep 2023 06:46:04 -0400 X-MC-Unique: Tf0999twN-mjlLwjFk9DVQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A3AF69115E0; Fri, 8 Sep 2023 10:46:03 +0000 (UTC) Received: from localhost (unknown [10.39.193.245]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1D75A40C2070; Fri, 8 Sep 2023 10:46:02 +0000 (UTC) Date: Fri, 8 Sep 2023 06:46:01 -0400 From: Stefan Hajnoczi To: Kevin Wolf Cc: qemu-devel@nongnu.org, mst@redhat.com, quintela@redhat.com, peterx@redhat.com, leobras@redhat.com, pbonzini@redhat.com, qemu-block@nongnu.org, qemu-stable@nongnu.org Subject: Re: [PATCH 2/2] virtio: Drop out of coroutine context in virtio_load() Message-ID: <20230908104601.GB3552950@fedora> References: <20230905145002.46391-1-kwolf@redhat.com> <20230905145002.46391-3-kwolf@redhat.com> <20230907184031.GA1560640@fedora> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="PPdE0F5nClV7eDAK" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --PPdE0F5nClV7eDAK Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Sep 08, 2023 at 10:59:48AM +0200, Kevin Wolf wrote: > Am 07.09.2023 um 20:40 hat Stefan Hajnoczi geschrieben: > > On Tue, Sep 05, 2023 at 04:50:02PM +0200, Kevin Wolf wrote: > > > virtio_load() as a whole should run in coroutine context because it > > > reads from the migration stream and we don't want this to block. > >=20 > > Is that "should" a "must" or a "can"? > >=20 > > If it's a "must" then virtio_load() needs assert(qemu_in_coroutine()). > >=20 > > But the previous patch mentioned that loadvm for snapshots calls it > > outside coroutine context. So maybe it's a "can"? >=20 > Where this makes a difference is when the function indirectly calls into > QIOChannel. When called from a coroutine, it yields while waiting for > I/O, and outside of a coroutine it blocks. Yielding is always > preferable, but in cases like HMP savevm/loadvm we also don't really > care because it's synchronous anyway. >=20 > Whether that makes it a MAY or a SHOULD in the RFC sense, you decide. > If you wanted to make it a MUST, you'd need to check all callers first > and change some of them. Thanks for clarifying. It is "can". Stefan --PPdE0F5nClV7eDAK Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmT6+2kACgkQnKSrs4Gr c8jd6ggAgZKLB5sQOoDOXsAlEWHSUwUmUt3dLYeVVRpD4MOcgZG2ikWD8griybuf mZ+OF4X/A2PfEna3pZ+xL2I4s0qIRLLE+Yjdf+wp0FsR+xQO7tWOYez5fF9KkB1Q l6iKqMYh1U1kBwdxHgdL4/OkEE7YTbeLiHmjcpTqeHuaslWpA8R1lou63dU2o4q2 mvc3ziEd0px66og6TK5PiA82nod+RP4Nch6Z3W/1Tq9UAKNA9YjytpoymwI9WkmB bjJfpa/UYnCKYeETGu28R47ZLZBKWyZRDGI8DPS/VxfCAFng0Jzk/whyKdtt1jLC /AicbI9LUqMqrumedjVsZmN1tOyZTg== =ZoFz -----END PGP SIGNATURE----- --PPdE0F5nClV7eDAK--