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 92F9FC4332F for ; Tue, 29 Nov 2022 17:53:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Subject:Cc:To:From:Message-ID:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=xuJN3dw0eYduUT+7/YoIUI+71EcsOhI1qDTE2AhWa7I=; b=fI66bVo4xu1di3 sndjarv/02aU9iYJ467BlcSUHbt8HvscXmU+0F7ZBn/xo80bxRR6ISQ7iz2jvFd0l9/HQigvYjlyg C8ttA2sOZxvgAS9R7nOuhsg2RODKZWrOBOi8q9/Rkg/3hPkyxA59WPFOp0eSInNi4L7JGgMmL3bUs xV6QL6ZRRkm9oAfk5TPjZd1HArPNTt1joOlKcl4wx0lvvmwDa+1cA8G5UhqhpPQ0Y32Is2xts84+w tcBcbcgFFZZbcGY+98dwrJ4azotYZYTT4GHL+POGQ1DV3KZDOjp6/4/i6F6lGVCQWjNW8iNiDnmYl kiCS7bDi/6C/2ho+8CPg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1p04m6-00Ae3j-3J; Tue, 29 Nov 2022 17:52:06 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1p04m3-00Ae32-JK for linux-arm-kernel@lists.infradead.org; Tue, 29 Nov 2022 17:52:04 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E9F4F61840; Tue, 29 Nov 2022 17:52:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 528AAC433D6; Tue, 29 Nov 2022 17:52:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669744322; bh=0O2FPwpNMkhH/XRL6oLiRwauafRbSb0wMWorXuWj45U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qACeQkZxwgJvYHp5DHR2yfDN3zQ7WOEObkPD9hqIPh63hVP14vvlcQWA/691erpsn KPGBz5g8xa1KlhmEa7m13F/jEmVLkFiETUmRMtbqz+dbNAfcdPcTWHIBXGCWCq/Lep o3WBrfS9OUgue/n4OJFSPPHKMnhlt73l4tO1wFtqDW0TBBy2ViqextE8SIocdMKPiG 3/ySW63hrd2XMoptbGDQE/fXrPXozdTcLRUSLJ2Zn5wXQc1zFPHtdpbmwT2/1LO1RC P3MUekfQAXgwM+u/TfSmjeo3W8Lor8CqyEAYMRlj0waqRv1lqkmBzj5eiO6dZZM/Wv ggBimumykEWoQ== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1p04m0-009PuC-3J; Tue, 29 Nov 2022 17:52:00 +0000 Date: Tue, 29 Nov 2022 17:51:59 +0000 Message-ID: <86edtlmyww.wl-maz@kernel.org> From: Marc Zyngier To: Ard Biesheuvel Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, anshuman.khandual@arm.com, mark.rutland@arm.com Subject: Re: [PATCH v2] arm64: mm: Align PGDs to at least 64 bytes In-Reply-To: <20221129143012.1806274-1-ardb@kernel.org> References: <20221129143012.1806274-1-ardb@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: ardb@kernel.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, anshuman.khandual@arm.com, mark.rutland@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221129_095203_694700_3B2749CA X-CRM114-Status: GOOD ( 20.45 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 29 Nov 2022 14:30:12 +0000, Ard Biesheuvel wrote: > > My copy of the ARM ARM (DDI 0487I.a) no longer describes the 64 byte > minimum alignment of root page tables as being conditional on whether > 52-bit physical addressing is supported and enabled, even though I seem > to remember that this was the case formerly (and our code suggests the > same). > > Section D17.2.144 "TTBR0_EL1, Translation Table Base Register 0 (EL1)" > contains the following wording: > > ----Note---- > A translation table is required to be aligned to the size of the > table. If a table contains fewer than eight entries, it must be > aligned on a 64 byte address boundary > > So align pgd_t[] allocations to 64 bytes. Note that this change only > affects 16k/4 levels configurations, which are unlikely to be in wide > use. > > Signed-off-by: Ard Biesheuvel > Acked-by: Catalin Marinas After the VTTBR discussion, and to be extra sure of this, I reached out to ARM and asked for clarification. As it turns out, the omission of the "> 48 bits" restriction is an unfortunate specification bug, and the old behaviour still applies (Rule KBLCR is also wrong). Can't wait for the next revision! ;-) M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel