From patchwork Fri Jan 19 13:57:46 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 13523810 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 BE6BBC47DAF for ; Fri, 19 Jan 2024 13:59:38 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rQpOG-0004hb-CE; Fri, 19 Jan 2024 08:58:36 -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 1rQpOA-0004Uu-B9 for qemu-devel@nongnu.org; Fri, 19 Jan 2024 08:58:31 -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 1rQpO4-0000YD-5l for qemu-devel@nongnu.org; Fri, 19 Jan 2024 08:58:29 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1705672702; 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=+Rk6942XyH/VX2bOHvbeFM89fcGmgkQjl81ORVJ0QBY=; b=ae3/Lgpx8F6uWi8e2mgU8fbR7fmlgaWK8DP9Li0zDNT2Hz4oi9sror+XGCQobFEOIL3lLz WRZYI21nGZU/BOOLtuEG5phR6wriyumhX2jfcf555HiROTzqL8Fj5HPLve/Lukb1JrxB0s SMlFgVNxjq2kvnqpfQkXXGlZNyTYA8A= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-677-C-yg1EimOAmVbBbp8S_lyg-1; Fri, 19 Jan 2024 08:58:21 -0500 X-MC-Unique: C-yg1EimOAmVbBbp8S_lyg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (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 27DA91C05134; Fri, 19 Jan 2024 13:58:21 +0000 (UTC) Received: from localhost (unknown [10.39.195.31]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7F5BE492BE2; Fri, 19 Jan 2024 13:58:20 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi , Thomas Huth , Hanna Reitz , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , qemu-block@nongnu.org, "Michael S. Tsirkin" , Kevin Wolf , Paolo Bonzini , =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= Subject: [PATCH 4/6] virtio-blk: restart s->rq reqs in vq AioContexts Date: Fri, 19 Jan 2024 08:57:46 -0500 Message-ID: <20240119135748.270944-5-stefanha@redhat.com> In-Reply-To: <20240119135748.270944-1-stefanha@redhat.com> References: <20240119135748.270944-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 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: -45 X-Spam_score: -4.6 X-Spam_bar: ---- X-Spam_report: (-4.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.519, 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, 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org A virtio-blk device with the iothread-vq-mapping parameter has per-virtqueue AioContexts. It is not thread-safe to process s->rq requests in the BlockBackend AioContext since that may be different from the virtqueue's AioContext to which this request belongs. The code currently races and could crash. Adapt virtio_blk_dma_restart_cb() to first split s->rq into per-vq lists and then schedule a BH each vq's AioContext as necessary. This way requests are safely processed in their vq's AioContext. Signed-off-by: Stefan Hajnoczi --- hw/block/virtio-blk.c | 44 ++++++++++++++++++++++++++++++++----------- 1 file changed, 33 insertions(+), 11 deletions(-) diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index e342cb2cfb..4525988d92 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -1156,16 +1156,11 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq) static void virtio_blk_dma_restart_bh(void *opaque) { - VirtIOBlock *s = opaque; + VirtIOBlockReq *req = opaque; + VirtIOBlock *s = req->dev; /* we're called with at least one request */ - VirtIOBlockReq *req; MultiReqBuffer mrb = {}; - WITH_QEMU_LOCK_GUARD(&s->rq_lock) { - req = s->rq; - s->rq = NULL; - } - while (req) { VirtIOBlockReq *next = req->next; if (virtio_blk_handle_request(req, &mrb)) { @@ -1195,16 +1190,43 @@ static void virtio_blk_dma_restart_cb(void *opaque, bool running, RunState state) { VirtIOBlock *s = opaque; + uint16_t num_queues = s->conf.num_queues; if (!running) { return; } - /* Paired with dec in virtio_blk_dma_restart_bh() */ - blk_inc_in_flight(s->conf.conf.blk); + /* Split the device-wide s->rq request list into per-vq request lists */ + g_autofree VirtIOBlockReq **vq_rq = g_new0(VirtIOBlockReq *, num_queues); + VirtIOBlockReq *rq; - aio_bh_schedule_oneshot(blk_get_aio_context(s->conf.conf.blk), - virtio_blk_dma_restart_bh, s); + WITH_QEMU_LOCK_GUARD(&s->rq_lock) { + rq = s->rq; + s->rq = NULL; + } + + while (rq) { + VirtIOBlockReq *next = rq->next; + uint16_t idx = virtio_get_queue_index(rq->vq); + + rq->next = vq_rq[idx]; + vq_rq[idx] = rq; + rq = next; + } + + /* Schedule a BH to submit the requests in each vq's AioContext */ + for (uint16_t i = 0; i < num_queues; i++) { + if (!vq_rq[i]) { + continue; + } + + /* Paired with dec in virtio_blk_dma_restart_bh() */ + blk_inc_in_flight(s->conf.conf.blk); + + aio_bh_schedule_oneshot(s->vq_aio_context[i], + virtio_blk_dma_restart_bh, + vq_rq[i]); + } } static void virtio_blk_reset(VirtIODevice *vdev)