Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756058AbdCGSoy (ORCPT ); Tue, 7 Mar 2017 13:44:54 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:33860 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755973AbdCGSoh (ORCPT ); Tue, 7 Mar 2017 13:44:37 -0500 Date: Tue, 7 Mar 2017 07:15:28 -0800 From: Christoph Hellwig To: "Austin S. Hemmelgarn" Cc: Christoph Hellwig , "David F." , linux-kernel , "linux-raid@vger.kernel.org" Subject: Re: When will Linux support M2 on RAID ? Message-ID: <20170307151528.GA16216@infradead.org> References: <20170307045200.GA1708@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.1 (2016-10-04) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1047 Lines: 17 On Tue, Mar 07, 2017 at 09:50:22AM -0500, Austin S. Hemmelgarn wrote: > He's referring to the RAID mode most modern Intel chipsets have, which (last > I checked) Linux does not support completely and many OEM's are setting by > default on new systems because it apparently provides better performance > than AHCI even for a single device. It actually provides worse performance. What it does it that it shoves up to three nvme device bars into the bar of an AHCI device, and requires the OS to handle them all using a single driver. The Money's on crack at Intel decided to do that to provide their "valueable" RSTe IP (which is a windows ATA + RAID driver in a blob, which now has also grown a NVMe driver). The only remotely sane thing is to disable it in the bios, and burn all people involved with it. The next best thing is to provide a fake PCIe root port driver untangling this before it hits the driver, but unfortunately Intel is unwilling to either do this on their own or at least provide enough documentation for others to do it.