From patchwork Thu Aug 4 18:17:13 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Eugenio Perez Martin X-Patchwork-Id: 1663792 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=OS60kcMn; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) 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 bilbo.ozlabs.org (Postfix) with ESMTPS id 4LzHCq70P5z9rx7 for ; Fri, 5 Aug 2022 04:23:19 +1000 (AEST) Received: from localhost ([::1]:60824 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oJfV8-0004Rh-0r for incoming@patchwork.ozlabs.org; Thu, 04 Aug 2022 14:23:18 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60900) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oJfPv-0005zJ-4l for qemu-devel@nongnu.org; Thu, 04 Aug 2022 14:17:59 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:59623) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oJfPs-0001Eq-3c for qemu-devel@nongnu.org; Thu, 04 Aug 2022 14:17:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1659637071; 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=buucNH6UPudgudlKQDxV5Skj8xgGaEiYKwfKh+0154k=; b=OS60kcMnGYfaecKqEoL03tytjWcw/3u1FKEsuJy6LaoaKBZhqhNbW0eVB4OWRnxZdOCLEX zFWqSYNfVvt07C5exia8uXomBevlH4ta5MHwzNpRLU9qNb6FzTfN+hIP91XWnqOEXeWCjy eehBXzuhJLepXb9HXYC7sN4nBKJpdw8= 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-132-uBiaOGByPP20Y8RgoGCBNQ-1; Thu, 04 Aug 2022 14:17:48 -0400 X-MC-Unique: uBiaOGByPP20Y8RgoGCBNQ-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 348A48057B9; Thu, 4 Aug 2022 18:17:38 +0000 (UTC) Received: from eperezma.remote.csb (unknown [10.39.192.132]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2E7B9492C3B; Thu, 4 Aug 2022 18:17:35 +0000 (UTC) From: =?utf-8?q?Eugenio_P=C3=A9rez?= To: qemu-devel@nongnu.org Cc: Stefano Garzarella , "Gonglei (Arei)" , Cornelia Huck , Liuxiangdong , "Michael S. Tsirkin" , Jason Wang , Gautam Dawar , Laurent Vivier , Eli Cohen , Zhu Lingshan , Cindy Lu , Stefan Hajnoczi , Parav Pandit , Paolo Bonzini , Harpreet Singh Anand , Eric Blake , Markus Armbruster Subject: [PATCH v6 03/12] vhost: Delete useless read memory barrier Date: Thu, 4 Aug 2022 20:17:13 +0200 Message-Id: <20220804181722.701067-4-eperezma@redhat.com> In-Reply-To: <20220804181722.701067-1-eperezma@redhat.com> References: <20220804181722.701067-1-eperezma@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eperezma@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" As discussed in previous series [1], this memory barrier is useless with the atomic read of used idx at vhost_svq_more_used. Deleting it. [1] https://lists.nongnu.org/archive/html/qemu-devel/2022-07/msg02616.html Signed-off-by: Eugenio Pérez --- hw/virtio/vhost-shadow-virtqueue.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c index e6eebd0e8d..1b49bf54f2 100644 --- a/hw/virtio/vhost-shadow-virtqueue.c +++ b/hw/virtio/vhost-shadow-virtqueue.c @@ -509,9 +509,6 @@ size_t vhost_svq_poll(VhostShadowVirtqueue *svq) if (unlikely(g_get_monotonic_time() - start_us > 10e6)) { return 0; } - - /* Make sure we read new used_idx */ - smp_rmb(); } while (true); }