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_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 5ECAAC433DF for ; Tue, 23 Jun 2020 16:27:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3B43F206D4 for ; Tue, 23 Jun 2020 16:27:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732694AbgFWQ14 (ORCPT ); Tue, 23 Jun 2020 12:27:56 -0400 Received: from verein.lst.de ([213.95.11.211]:39847 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732212AbgFWQ1z (ORCPT ); Tue, 23 Jun 2020 12:27:55 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 078AE68AEF; Tue, 23 Jun 2020 18:27:52 +0200 (CEST) Date: Tue, 23 Jun 2020 18:27:51 +0200 From: Christoph Hellwig To: Baolin Wang Cc: kbusch@kernel.org, axboe@fb.com, hch@lst.de, sagi@grimberg.me, baolin.wang7@gmail.com, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] nvme-pci: Add controller memory buffer supported macro Message-ID: <20200623162751.GA4846@lst.de> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 23, 2020 at 09:24:33PM +0800, Baolin Wang wrote: > Introduce a new capability macro to indicate if the controller > supports the memory buffer or not, instead of reading the > NVME_REG_CMBSZ register. This is a complex issue. The CMBS bit was only added in NVMe 1.4 as a backwards incompatible change, as the CMB addressing scheme can lead to data corruption. The CMBS was added as part of the horribe hack that also involves the CBA field, which we'll need to see before using it to work around the addressing issue. At the same time we should also continue supporting the legacy pre-1.4 CMB with a warning (and may reject it if we know we run in a VM).