From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20FD1C4321D for ; Thu, 16 Aug 2018 14:15:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CEB442148C for ; Thu, 16 Aug 2018 14:15:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CEB442148C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391719AbeHPROF (ORCPT ); Thu, 16 Aug 2018 13:14:05 -0400 Received: from mga04.intel.com ([192.55.52.120]:28055 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726312AbeHPROF (ORCPT ); Thu, 16 Aug 2018 13:14:05 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Aug 2018 07:15:12 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,247,1531810800"; d="scan'208";a="83855657" Received: from unknown (HELO localhost.localdomain) ([10.232.112.44]) by orsmga002.jf.intel.com with ESMTP; 16 Aug 2018 07:15:11 -0700 Date: Thu, 16 Aug 2018 08:15:59 -0600 From: Keith Busch To: Michal Wnukowski Cc: "torvalds@linux-foundation.org" , "axboe@fb.com" , "hch@lst.de" , "keith.busch@linux.intel.com" , "linux-kernel@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "sagi@grimberg.me" , "yigitfiliz@google.com" Subject: Re: [PATCH v2] Bugfix for handling of shadow doorbell buffer. Message-ID: <20180816141558.GB5438@localhost.localdomain> References: <20180815225157.89523-1-wnukowski@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180815225157.89523-1-wnukowski@google.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 15, 2018 at 03:51:57PM -0700, Michal Wnukowski wrote: > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c > index 17a0190bd88f..4452f8553301 100644 > --- a/drivers/nvme/host/pci.c > +++ b/drivers/nvme/host/pci.c > @@ -306,6 +306,14 @@ static bool nvme_dbbuf_update_and_check_event(u16 value, u32 *dbbuf_db, > old_value = *dbbuf_db; > *dbbuf_db = value; > > + /* > + * Ensure that the doorbell is updated before reading > + * the EventIdx from memory. NVMe controller should have > + * similar ordering guarantees - update EventIdx before > + * reading doorbell. > + */ > + mb(); > + > if (!nvme_dbbuf_need_event(*dbbuf_ei, value, old_value)) > return false; > } Looks good to me. This should also be a stable candidate. Reviewed-by: Keith Busch