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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 E734BC433EF for ; Thu, 5 May 2022 13:45:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=GFRL3ix/UPm8SMm593rYrUUeWtJXduBSS44WUgj2q8U=; b=QLjG4V9jam58I82N36ZuuJOi+1 QkUvYiwiLHLpJQRKZEnZ4S1WVnGLX4X0uMj3TWconNwobk+rj2fmQvHPszqbA+pCd63admzWjYS9X K3Dcz1A+Jktkh08ifN2qGoWa5xT9XF9psuYEyCsrSjSYplX2jhhDwKDJPDY/B89DHD4Qr17XWCt/K KmGlje9k+1yUqYB7Vky7m9Aob9pGBgDWy2N3wtGPN4QfrvpffNu7Tn3umPR49IGA0Z8O98WTQbDjD nVNoFqmoTiJzCbYmh6+lZFLfmLI0NkD/BfqVX2v89Epc1t90a1zmtRRE9QpVQhsi49O4xcdt/1Q0y EwLwjFhA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nmbng-00G7z6-1q; Thu, 05 May 2022 13:45:48 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nmbnW-00G7u2-5J for linux-nvme@lists.infradead.org; Thu, 05 May 2022 13:45:44 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 58F3168AA6; Thu, 5 May 2022 15:45:34 +0200 (CEST) Date: Thu, 5 May 2022 15:45:34 +0200 From: Christoph Hellwig To: Keith Busch Cc: linux-nvme@lists.infradead.org, hch@lst.de, Keith Busch Subject: Re: [PATCH] nvme: set dma alignment to 3 Message-ID: <20220505134533.GA13926@lst.de> References: <20220504184325.1439476-1-kbusch@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220504184325.1439476-1-kbusch@fb.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220505_064538_376796_86654B2B X-CRM114-Status: GOOD ( 14.60 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Wed, May 04, 2022 at 11:43:25AM -0700, Keith Busch wrote: > From: Keith Busch > > The nvme specification only requires qword alignment for segment > descriptors, and the driver already guarantees that. The spec has always > allowed user data to be dword aligned, which is what the queue's > attribute is for, so relax the alignment requirement to that value. > > While we could allow byte alignment for some controllers when using > SGLs, we still need to support PRP, and that only allows dword. Can't we just turn it go up to eleven? ;-)