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 X-Spam-Level: X-Spam-Status: No, score=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DB20C4361B for ; Mon, 7 Dec 2020 16:59:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C65D023888 for ; Mon, 7 Dec 2020 16:59:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727805AbgLGQ7c (ORCPT ); Mon, 7 Dec 2020 11:59:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35340 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727352AbgLGQ7c (ORCPT ); Mon, 7 Dec 2020 11:59:32 -0500 Received: from mail-ej1-x642.google.com (mail-ej1-x642.google.com [IPv6:2a00:1450:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB9A8C061749 for ; Mon, 7 Dec 2020 08:58:51 -0800 (PST) Received: by mail-ej1-x642.google.com with SMTP id lt17so20541052ejb.3 for ; Mon, 07 Dec 2020 08:58:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=ODFYNKTjMTwnPrK31rw4SLzGgzSU67H0O2yeRZFdhqE=; b=StWv8dDxId3OKQIuDuKxj9jQNu0m2dzeV78062mOPIKyxMU89QJYro/YNl6/gjoSSS v+t8vX/HJok65OHBMUd/BtXcUpWPE5Ub+gyBQOwt1/2u/C8p+9CU+1Mcr4dA+Y14w57i 45c9afhRrA+LOIgaVY/Kd651s2f0piLIcWD4/ZPGUokK04B51HiNdCtNJ238uJfgGUcE rw4cg4ji6epNW5tAC0WMjVbnEYY1SQjxkYzqX3FZ/JoKmSLH1MrT7IFpcIu3FPLfnUTb s+MZhd9GtEOIS4n+mXJNrCelojEWWRysYkGqyQ3LzTTqgH5FkkH79xzDO9SGVNseGj6i Q13g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=ODFYNKTjMTwnPrK31rw4SLzGgzSU67H0O2yeRZFdhqE=; b=bHQY7mWAM19jAvhY85NqzRWXW+hnd6DVZvJpUyOO0KR51ZAfH/I4sR5j9aYG5vhcm8 lzrGDxFtXPRpsZO8mpsFoOChzcvqDTQLZkS21RHS6PzG33NeJwlqXuIZvmNqQfrd0/hE KROFv+3YH9+nPrKpbhwyhBihV+lxeKIwBi2mmhl1jxWZ0K9bNixSXKNiXW+belUThW6I GfCVsDW3dI9UObgACbinbonUmZ0tyi+UwgFY7w1U3P89umML/EmjdY+/U/3PhyZfNMv6 YqYDM/BTQpNYKHL7DX2nrali75U7/d/sXKqkbpbamU47dvJ4F8Q2Z+oJjm9goGkAd3Yt ZqvA== X-Gm-Message-State: AOAM531g70erDa6fUTpZchSXzAjE2C82MV1lc0WzXl67lJbEipwcQutF 1rOvZRKEbFXwhWJHiq1eDo4= X-Google-Smtp-Source: ABdhPJzHOW+Ylwqjw+on2+NxIj8szkbB93r8R6R4oPxzlBCIMpXESI+nx/IQwtqoqUYOs2yYBcEfMQ== X-Received: by 2002:a17:907:447d:: with SMTP id oo21mr19969752ejb.367.1607360330523; Mon, 07 Dec 2020 08:58:50 -0800 (PST) Received: from localhost ([51.15.41.238]) by smtp.gmail.com with ESMTPSA id n1sm12853926ejb.2.2020.12.07.08.58.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Dec 2020 08:58:49 -0800 (PST) Date: Mon, 7 Dec 2020 16:58:48 +0000 From: Stefan Hajnoczi To: Eugenio =?iso-8859-1?Q?P=E9rez?= Cc: qemu-devel@nongnu.org, Lars Ganrot , virtualization@lists.linux-foundation.org, Salil Mehta , "Michael S. Tsirkin" , Liran Alon , Rob Miller , Max Gurtovoy , Alex Barba , Stefan Hajnoczi , Jim Harford , Jason Wang , Harpreet Singh Anand , Christophe Fontaine , vm , Daniel Daly , Michael Lilja , Stefano Garzarella , Nitin Shrivastav , Lee Ballard , Dmytro Kazantsev , Juan Quintela , kvm@vger.kernel.org, Howard Cai , Xiao W Wang , Sean Mooney , Parav Pandit , Eli Cohen , Siwei Liu , Stephen Finucane Subject: Re: [RFC PATCH 06/27] virtio: Add virtio_queue_get_used_notify_split Message-ID: <20201207165848.GM203660@stefanha-x1.localdomain> References: <20201120185105.279030-1-eperezma@redhat.com> <20201120185105.279030-7-eperezma@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="EOHJn1TVIJfeVXv2" Content-Disposition: inline In-Reply-To: <20201120185105.279030-7-eperezma@redhat.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org --EOHJn1TVIJfeVXv2 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Nov 20, 2020 at 07:50:44PM +0100, Eugenio P=E9rez wrote: > This function is just used for a few commits, so SW LM is developed > incrementally, and it is deleted after it is useful. >=20 > For a few commits, only the events (irqfd, eventfd) are forwarded. s/eventfd/ioeventfd/ (irqfd is also an eventfd) > +bool virtio_queue_get_used_notify_split(VirtQueue *vq) > +{ > + VRingMemoryRegionCaches *caches; > + hwaddr pa =3D offsetof(VRingUsed, flags); > + uint16_t flags; > + > + RCU_READ_LOCK_GUARD(); > + > + caches =3D vring_get_region_caches(vq); > + assert(caches); > + flags =3D virtio_lduw_phys_cached(vq->vdev, &caches->used, pa); > + return !(VRING_USED_F_NO_NOTIFY & flags); > +} QEMU stores the notification status: void virtio_queue_set_notification(VirtQueue *vq, int enable) { vq->notification =3D enable; <---- here if (!vq->vring.desc) { return; } if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) { virtio_queue_packed_set_notification(vq, enable); } else { virtio_queue_split_set_notification(vq, enable); I'm wondering why it's necessary to fetch from guest RAM instead of using vq->notification? It also works for both split and packed queues so the code would be simpler. --EOHJn1TVIJfeVXv2 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAl/OX0gACgkQnKSrs4Gr c8joJwgAxP2IQdibt4q6jUVfHjl/jy+5PpzROcRTI3+NTOW7RZAtHwg1VSLc+N8N AGRSKiaMpsWS/ApNmdzTjrmMurFOZRjrsPVwu+UDqsd1vscYk9ZWhc3vS24gYSot X9Y0av+ZpV0OBKlFGpEdqaOHt7LuK/IwyZe5fXGH0CAH25+OKky7gisAMXeY9c3L CEusJ6PGE4fr+99IcJcefGiMPCW6QvmJQnvsq2F7ST1ArsPfhvZASZWnucmtXsNH YywpV+RFNQrbyiMU86CwVE99COm16dTpb1n4QHu5+4tTQa9l3wy9cKTPrrFzlUGI Wm8tTPQ1Njha3wNnYaoHBGcNMX0sCg== =RgXt -----END PGP SIGNATURE----- --EOHJn1TVIJfeVXv2--