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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1758282568; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UeCv59JB3G6AoNIDuRn03RdiRvm7Zc9pTM71DO+CB/w=; b=5GXxkuqwTlh1HX32Vd5LysTMsRN+9P9+uVGPFTooN4N2vMRoR82SfZZSE136RGS330RMd4 bw4zcSGNGnzGUVanmvVGJdCBQ/cLv5WkAO3DfCxYYcUKNrShf6hGVsguHzaBDVyA2fJ1ie knycOjL0NIlbF2wOk7bO2t9hBh6zNsg= 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-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 486C480006 X-Stat-Signature: 9yexo1n5iy4rupc9jz5sdcik6nu83th9 X-Rspam-User: X-HE-Tag: 1758282568-22508 X-HE-Meta: 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 Lrs2W3Zc GMPHaZyweXvk/1DEhRywfSb4vtWKIus8P4V5WfR/rTp97lI+H3l2T7iz2kB1Eky0UeC/+b70V6rvxWDkA6A6y28w1xhT/qHpSrnrD6NpngpaLEujKHUjTUiqkR9+9g4hjWWdCq3M1eOBYb/SDcI5zcsqWG0B+8FS5fl8Y2SXTk8O6KQtvK6Z8KwfZIfSa48WkriZfd1gFuZdta57ayMH9drBBgg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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