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 68DD7CD98C5 for ; Wed, 10 Jun 2026 05:12:00 +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=2GJ7Pj5chXa9KIYTVJaZOEQTB9a9MC+ilmCUwbWdCWU=; b=po6dwVCBecb424/lraftfzLhYZ rcC1Wcj+LNfx+aBfTvWHjLALZwndifIgekWXvXFU6KFY1UrOKPivXhS6Ey/5sHvI9rhkSbxrWYw3y iGWIunm++osGKrjrhXMA0qYGsyGg+f5DNN0OCPXBihJS9KXSVTnwwCjznaHmPbAGJLOHiWoVNrRld abFDoiZWPzKkYKT9+d6NgcB0wOWsY4MhYvaj5bGyXZ4biGwFvblfDTT9jiZ9w6sR+mZQhsXBDrjr2 onyEvnaO5rGwBqw1Bm4VKkrw3BqQQPDH+NWQtrInrbk1dfiIQ5ET8mikDrpjDB69Gnl3kHF3/xQph OpJ9s7PA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wXBEH-00000006oMw-4Br9; Wed, 10 Jun 2026 05:11:54 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wXBEF-00000006oMR-1YDl; Wed, 10 Jun 2026 05:11:52 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id B6F1168BEB; Wed, 10 Jun 2026 07:11:46 +0200 (CEST) Date: Wed, 10 Jun 2026 07:11:46 +0200 From: Christoph Hellwig To: Nick Chan Cc: Sven Peter , Janne Grunau , Neal Gompa , Keith Busch , Jens Axboe , Christoph Hellwig , Sagi Grimberg , asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/2] nvme-apple: Only limit admin queue tag space when with Linear SQ is present Message-ID: <20260610051146.GA559@lst.de> References: <20260606-prevent-tag-collision-t8015-v1-0-93ccf4eca550@gmail.com> <20260606-prevent-tag-collision-t8015-v1-1-93ccf4eca550@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260606-prevent-tag-collision-t8015-v1-1-93ccf4eca550@gmail.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260609_221151_578657_934233DF X-CRM114-Status: GOOD ( 14.19 ) X-BeenThere: linux-arm-kernel@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-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat, Jun 06, 2026 at 09:25:25PM +0800, Nick Chan wrote: > Apple NVMe controllers require tags of pending commands to not be shared > across admin and IO queues. However, on Apple A11 without linear SQ, it is > not possible for either queue to skip over some tags and must go from 0 to > the configured maximum before wrapping around. > > As a result, in order to prevent tag collision, dynamic tag reservation > while a command is in-flight becomes necessary. In this context, there is > no reason to limit the admin queue's tag space, as it is not helpful in > preventing tag collision. I'm not really into these Apple specific, but what does "dynamic tag reservation" mean here?