From nobody Tue Nov 18 22:46:03 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1613473576070972.7819156577821; Tue, 16 Feb 2021 03:06:16 -0800 (PST) Received: from localhost ([::1]:52734 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lByBL-0008L7-12 for importer@patchew.org; Tue, 16 Feb 2021 06:06:15 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:54778) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lBy6N-0004Dt-PF for qemu-devel@nongnu.org; Tue, 16 Feb 2021 06:01:07 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:37501) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lBy6K-0003nk-Ab for qemu-devel@nongnu.org; Tue, 16 Feb 2021 06:01:07 -0500 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-480-uEBUz2LhP_yChkGyWqYfVA-1; Tue, 16 Feb 2021 06:01:02 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D38C0801962; Tue, 16 Feb 2021 11:01:00 +0000 (UTC) Received: from thuth.com (ovpn-112-157.ams2.redhat.com [10.36.112.157]) by smtp.corp.redhat.com (Postfix) with ESMTP id 73C18226F0; Tue, 16 Feb 2021 11:00:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613473263; 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; bh=5lf2YSXRu/jZWVdx7C+hA17219f6W1Eg56+V8+YUNSk=; b=ePC6OpwemMit/LeTfvtiYmkAO9s6kes+zgfZmCAaH/rCSN37ULL1qVHdoV7L8nyQEh9oqA vEdjpZACi/QMku4n2VRDI1ESZgO1srWReWH4dZCSpHQTBSqvx2467mOowFEXukMErUxTXJ 1ocs2YkuBkKCJ7sswuYBDVz93Aa7IQA= X-MC-Unique: uEBUz2LhP_yChkGyWqYfVA-1 From: Thomas Huth To: qemu-devel@nongnu.org, Cornelia Huck Subject: [PATCH] pc-bios/s390-ccw: Use memory barriers in virtio code Date: Tue, 16 Feb 2021 12:00:56 +0100 Message-Id: <20210216110056.1228582-1-thuth@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=63.128.21.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Christian Borntraeger , qemu-s390x@nongnu.org, Peter Maydell Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" According to the virtio specification, a memory barrier should be used before incrementing the idx field in the "available" ring. So far, we did not do this in the s390-ccw bios yet, but recently Peter Maydell saw problems with the s390-ccw bios when running the qtests on an aarch64 host (the bios panic'ed with the message: "SCSI cannot report LUNs: response VS RESP=3D09"), which could maybe be related to the missing memory barriers. Thus let's add those barriers now. Since we've only seen the problem on TCG so far, a "bcr 14,0" should be sufficient here to trigger the tcg_gen_mb() in the TCG translate code. (Note: The virtio spec also talks about using a memory barrier *after* incrementing the idx field, but if I understood correctly this is only required when using notification suppression - which we don't use in the s390-ccw bios here) Signed-off-by: Thomas Huth --- pc-bios/s390-ccw/virtio-net.c | 1 + pc-bios/s390-ccw/virtio.c | 1 + pc-bios/s390-ccw/virtio.h | 2 ++ 3 files changed, 4 insertions(+) diff --git a/pc-bios/s390-ccw/virtio-net.c b/pc-bios/s390-ccw/virtio-net.c index 2fcb0a58c5..25598a7a97 100644 --- a/pc-bios/s390-ccw/virtio-net.c +++ b/pc-bios/s390-ccw/virtio-net.c @@ -127,6 +127,7 @@ int recv(int fd, void *buf, int maxlen, int flags) =20 /* Mark buffer as available to the host again */ rxvq->avail->ring[rxvq->avail->idx % rxvq->num] =3D id; + virtio_mb(); rxvq->avail->idx =3D rxvq->avail->idx + 1; vring_notify(rxvq); =20 diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c index ab49840db8..fb9687f9b3 100644 --- a/pc-bios/s390-ccw/virtio.c +++ b/pc-bios/s390-ccw/virtio.c @@ -154,6 +154,7 @@ void vring_send_buf(VRing *vr, void *p, int len, int fl= ags) =20 /* Chains only have a single ID */ if (!(flags & VRING_DESC_F_NEXT)) { + virtio_mb(); vr->avail->idx++; } } diff --git a/pc-bios/s390-ccw/virtio.h b/pc-bios/s390-ccw/virtio.h index 19fceb6495..6ac65482a9 100644 --- a/pc-bios/s390-ccw/virtio.h +++ b/pc-bios/s390-ccw/virtio.h @@ -271,6 +271,8 @@ struct VirtioCmd { }; typedef struct VirtioCmd VirtioCmd; =20 +#define virtio_mb() asm volatile("bcr 14,0" : : : "memory") + bool vring_notify(VRing *vr); int drain_irqs(SubChannelId schid); void vring_send_buf(VRing *vr, void *p, int len, int flags); --=20 2.27.0