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 50D1DCAC59A for ; Fri, 19 Sep 2025 11:49:42 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=UeCv59JB3G6AoNIDuRn03RdiRvm7Zc9pTM71DO+CB/w=; b=p7n3CY8dhhSps56jAY+A7E5SxE DjQcXtOo+7XnprqMF7ljrsdtZNulrJMPK8U7vdxnVc3WPqTlxaJQeQMrwZ9JhjHpHQgs/B1PfX2D8 Yp1bQIajbqrbwuT6YapSki2nAPZvY0paC/UPZIBagxf+/MAeNAhvy63XGLloZbt/bZ7B7tIdxUG4U FPP2YhfUjjhkwg6qhO/0zMYWobbC2tD9Ia6oTO0T06Jek6VJXeWxjkMHzk1aOWMrlmH8eWUDSTAm5 xYAHPfpDyU5IRVhttB8TKb7inf0mjzH7hanB79LuJ2StKrihHK5U9bjTDQl+ynyzOEcaiN2HkQOOf Fzb832DA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uzZcK-00000002jf3-1gur; Fri, 19 Sep 2025 11:49:32 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uzZcH-00000002je4-07lf for linux-arm-kernel@lists.infradead.org; Fri, 19 Sep 2025 11:49:30 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 18CB71691; Fri, 19 Sep 2025 04:49:19 -0700 (PDT) Received: from [10.57.95.38] (unknown [10.57.95.38]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C34EB3F66E; Fri, 19 Sep 2025 04:49:24 -0700 (PDT) Message-ID: Date: Fri, 19 Sep 2025 12:49:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 0/5] arm64: support FEAT_BBM level 2 and large block mapping when rodata=full Content-Language: en-GB To: Will Deacon Cc: catalin.marinas@arm.com, akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, ardb@kernel.org, dev.jain@arm.com, scott@os.amperecomputing.com, cl@gentwo.org, Yang Shi , kernel-team@android.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20250917190323.3828347-1-yang@os.amperecomputing.com> <175822779944.710258.10028837182267037801.b4-ty@kernel.org> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250919_044929_115387_2D2CF6CF X-CRM114-Status: GOOD ( 17.64 ) 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 19/09/2025 12:27, Will Deacon wrote: > On Fri, Sep 19, 2025 at 11:08:47AM +0100, Ryan Roberts wrote: >> On 18/09/2025 22:10, Will Deacon wrote: >>> On Wed, 17 Sep 2025 12:02:06 -0700, Yang Shi wrote: >>>> On systems with BBML2_NOABORT support, it causes the linear map to be mapped >>>> with large blocks, even when rodata=full, and leads to some nice performance >>>> improvements. >>>> >>>> Ryan tested v7 on an AmpereOne system (a VM with 12G RAM) in all 3 possible >>>> modes by hacking the BBML2 feature detection code: >>>> >>>> [...] >>> >>> Applied patches 1 and 3 to arm64 (for-next/mm), thanks! >>> >>> [1/5] arm64: Enable permission change on arm64 kernel block mappings >>> https://git.kernel.org/arm64/c/a660194dd101 >>> [3/5] arm64: mm: support large block mapping when rodata=full >>> https://git.kernel.org/arm64/c/a166563e7ec3 >>> >>> I also picked up the BBML allow-list addition (second patch) on >>> for-next/cpufeature. >>> >>> The fourth patch ("arm64: mm: split linear mapping if BBML2 unsupported >>> on secondary CPUs") has some really horrible conflicts. These are partly >>> due to some of the type cleanups on for-next/mm but I think mainly due >>> to Kevin's kpti rework that landed after -rc1. >> >> Thanks Will, although I'm nervous that without this patch, some platforms might >> not boot; Wikipedia tells me that there are some Google, Mediatek and Qualcomm >> SoCs that pair X4 CPUs (which is on the BBML2_NOABORT allow list) with A720 >> and/or A520 (which are not). See previous mail at [1]. > > I'd be surprised if these SoCs are booting on the X4 but who knows. Ahh. You can probably tell I'm a bit naive to some of this system level stuff... I had assumed they would want to boot on the big CPU to reduce boot time. > > Lemme have another look at applying the patch with fresh eyes, but I do > wonder whether having X4 on the allow list really makes any sense. Are > there any SoCs out there that _don't_ pair it with CPUs that aren't on > the allow list? (apologies for the double negative). Hmm, that's a fair question. I'm not aware of any. So I guess the simplest solution is to remove X4 from the allow list and ditch fourth patch. > > Will