From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id B4FCFA0543; Thu, 7 Jul 2022 14:38:45 +0200 (CEST) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 938F8406B4; Thu, 7 Jul 2022 14:38:45 +0200 (CEST) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by mails.dpdk.org (Postfix) with ESMTP id 2CF724069D for ; Thu, 7 Jul 2022 14:38:44 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1657197523; 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=gAndNozsZ5kUHrj8MfmynkXYj7TeFQu+EWM2awFohe8=; b=PHOrVZtWy02InvRWi5mfsw5DeW9AJhjPBZ0MiEhfX4s+m9e+J7pfdiCi9qCtBBCeWtxv61 /wDVQCkptqNmhMQQuV8tg/4ocluRru+3CgJsusHp3gDaKAfuluNLYoRmHpwwCteqmv2piy Ha9wOtqcRfVqchDIJF9ePuTmqjmaQGI= 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-642-SWmoOjzPPNmc3eCf59OANQ-1; Thu, 07 Jul 2022 08:38:34 -0400 X-MC-Unique: SWmoOjzPPNmc3eCf59OANQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5B2688EFAEF; Thu, 7 Jul 2022 12:38:34 +0000 (UTC) Received: from [10.39.208.34] (unknown [10.39.208.34]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 37E952EF9E; Thu, 7 Jul 2022 12:38:33 +0000 (UTC) Message-ID: <04f993c8-24dc-aa76-9f02-faa4e6a25855@redhat.com> Date: Thu, 7 Jul 2022 14:38:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 To: abhimanyu.saini@xilinx.com, dev@dpdk.org Cc: chenbo.xia@intel.com, andrew.rybchenko@oktetlabs.ru, Abhimanyu Saini References: <20220706092401.36815-1-asaini@xilinx.com> From: Maxime Coquelin Subject: Re: [PATCH] vdpa/sfc: resolve race between libvhost and dev_conf In-Reply-To: <20220706092401.36815-1-asaini@xilinx.com> X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=maxime.coquelin@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On 7/6/22 11:24, abhimanyu.saini@xilinx.com wrote: > From: Abhimanyu Saini > > libvhost calls dev_conf() before prosessing the > VHOST_USER_SET_VRING_CALL message for the last VQ. So > this message is processed after dev_conf() returns. > > However, the dev_conf() function spawns a thread to set > rte_vhost_host_notifier_ctrl() before returning control to > libvhost. This parallel thread in turn invokes get_notify_area(). > To get the notify_area, the vdpa driver needs to query the HW and > for this query it needs an enabled VQ. > > But at the same time libvhost is processing the last > VHOST_USER_SET_VRING_CALL, and to do that it disables the last VQ. > > Hence there is a race b/w the libvhost and the vdpa driver. > > To resolve this race condition, query the HW and cache notify_area > inside dev_conf() instead of doing it the parallel thread. > > Signed-off-by: Abhimanyu Saini > --- > drivers/vdpa/sfc/sfc_vdpa_ops.c | 36 ++++++++++++++++++------------------ > drivers/vdpa/sfc/sfc_vdpa_ops.h | 1 + > 2 files changed, 19 insertions(+), 18 deletions(-) > During today's Release status meeting, Andrew mentioned that this patch has been for a log time already in your internal tree. So it gives a bit of confidence in taking it in -rc4. Reviewed-by: Maxime Coquelin Thanks, Maxime