From patchwork Fri Mar 1 08:09:49 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Huth X-Patchwork-Id: 1906574 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.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=YxmS+BHr; dkim-atps=neutral Authentication-Results: legolas.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=patchwork.ozlabs.org) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4TmLQL1XySz23fC for ; Fri, 1 Mar 2024 19:11:22 +1100 (AEDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rfxy8-0003IN-GP; Fri, 01 Mar 2024 03:10:12 -0500 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 1rfxy5-0003Hh-D2 for qemu-devel@nongnu.org; Fri, 01 Mar 2024 03:10:09 -0500 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 1rfxy2-0006lA-NO for qemu-devel@nongnu.org; Fri, 01 Mar 2024 03:10:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709280606; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gTEFAo3xmxDm8Q3byKcEbCr6cTkdhZCw58j4909TGwM=; b=YxmS+BHroRZ2x8phXqnmf2xmjm3xNoCYDaxfe2h4MbLHESiCX+T3zBpFycld/75UX1qFIZ YnVQ3f8fKpTGyZE8mJlh5iaMfXg7JFwdPrjpDgG/Ar9pWWC7qeRIFt6qIPCJxdxa91MqXw qzkGbGPpWiBLlrRHc+ZqaaHcUAgjI5A= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-323-Zh0qmV8QPy-n6sEFvy7LIw-1; Fri, 01 Mar 2024 03:09:58 -0500 X-MC-Unique: Zh0qmV8QPy-n6sEFvy7LIw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B4246848C21; Fri, 1 Mar 2024 08:09:57 +0000 (UTC) Received: from thuth-p1g4.redhat.com (unknown [10.39.193.125]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9F42D2015B7D; Fri, 1 Mar 2024 08:09:56 +0000 (UTC) From: Thomas Huth To: qemu-devel@nongnu.org Cc: Peter Maydell , Daniel Henrique Barboza , Alistair Francis Subject: [PULL 2/6] libqos/virtio.c: fix 'avail_event' offset in qvring_init() Date: Fri, 1 Mar 2024 09:09:49 +0100 Message-ID: <20240301080953.66448-3-thuth@redhat.com> In-Reply-To: <20240301080953.66448-1-thuth@redhat.com> References: <20240301080953.66448-1-thuth@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=thuth@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=-0.096, 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_H2=-0.001, 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-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Daniel Henrique Barboza In qvring_init() we're writing vq->used->avail_event at "vq->used + 2 + array_size". The struct pointed by vq->used is, from virtio_ring.h Linux header): * // A ring of used descriptor heads with free-running index. * __virtio16 used_flags; * __virtio16 used_idx; * struct vring_used_elem used[num]; * __virtio16 avail_event_idx; So 'flags' is the word right at vq->used. 'idx' is vq->used + 2. We need to skip 'used_idx' by adding + 2 bytes, and then sum the vector size, to reach avail_event_idx. An example on how to properly access this field can be found in qvirtqueue_kick(): avail_event = qvirtio_readw(d, qts, vq->used + 4 + sizeof(struct vring_used_elem) * vq->size); This error was detected when enabling the RISC-V 'virt' libqos machine. The 'idx' test from vhost-user-blk-test.c errors out with a timeout in qvirtio_wait_used_elem(). The timeout happens because when processing the first element, 'avail_event' is read in qvirtqueue_kick() as non-zero because we didn't initialize it properly (and the memory at that point happened to be non-zero). 'idx' is 0. All of this makes this condition fail because "idx - avail_event" will overflow and be non-zero: /* < 1 because we add elements to avail queue one by one */ if ((flags & VRING_USED_F_NO_NOTIFY) == 0 && (!vq->event || (uint16_t)(idx-avail_event) < 1)) { d->bus->virtqueue_kick(d, vq); } As a result the virtqueue is never kicked and we'll timeout waiting for it. Fixes: 1053587c3f ("libqos: Added EVENT_IDX support") Signed-off-by: Daniel Henrique Barboza Reviewed-by: Alistair Francis Reviewed-by: Thomas Huth Message-ID: <20240217192607.32565-3-dbarboza@ventanamicro.com> Signed-off-by: Thomas Huth --- tests/qtest/libqos/virtio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tests/qtest/libqos/virtio.c b/tests/qtest/libqos/virtio.c index 4f39124eba..82a6e122bf 100644 --- a/tests/qtest/libqos/virtio.c +++ b/tests/qtest/libqos/virtio.c @@ -265,7 +265,7 @@ void qvring_init(QTestState *qts, const QGuestAllocator *alloc, QVirtQueue *vq, /* vq->used->idx */ qvirtio_writew(vq->vdev, qts, vq->used + 2, 0); /* vq->used->avail_event */ - qvirtio_writew(vq->vdev, qts, vq->used + 2 + + qvirtio_writew(vq->vdev, qts, vq->used + 4 + sizeof(struct vring_used_elem) * vq->size, 0); }