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 A4187C433EF for ; Thu, 14 Jul 2022 01:54:20 +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-Type: List-Subscribe:List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: In-Reply-To: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=71DaWeGP8/yXcLH/ym0DUW67mFUAgfmksfQOlXx40Tw=; b=S5kR0NU2MZjrZsa4RrrB3BjONE L9tUtl9GPyJNItl5e/RbholUBEkdNgYUxaKyjoFJpN9rLYpCSsH/8QI+x8Ghy57z/OWx+atqvyQZo 70JPKTn5djVoDh4bTC5trcspfhMQ1SfBtCl+7YNNZi8RylJSKbyGiEEt4WSHMk2xaiE0MHVNEyY+U GJwG7q0VhFTuFDgyEGWJpXhkeBLKiKm47bV3GzGRGVS0mBwgUHkJT5nBLjE2z8Ue12LAJh5RNugZW Gue2tEJgWku5yqkRkDGq+RdF3yru1i+smsibd/LzZvbgujdic8/23F1ePzAnJ8Mb8m0b9KGXTOHHt s77jAm2A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oBo1n-009sKx-6O; Thu, 14 Jul 2022 01:52:31 +0000 Received: from cheddar.halon.org.uk ([93.93.131.118]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oBo1j-009sIL-GC for linux-arm-kernel@lists.infradead.org; Thu, 14 Jul 2022 01:52:29 +0000 Received: from wookey by cheddar.halon.org.uk with local (Exim 4.92) (envelope-from ) id 1oBo1X-0006z1-2G; Thu, 14 Jul 2022 02:52:15 +0100 Date: Thu, 14 Jul 2022 02:52:15 +0100 From: Wookey To: Ard Biesheuvel Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, arnd@arndb.de, will@kernel.org, mark.rutland@arm.com, maz@kernel.org, broonie@kernel.org, debian-arm@lists.debian.org, Vagrant Cascadian , Riku Voipio , Steve McIntyre Subject: Re: [PATCH v2] arm64: compat: Implement misalignment fixups for multiword loads Message-ID: <20220714015214.GP27816@mail.wookware.org> Mail-Followup-To: Ard Biesheuvel , linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, arnd@arndb.de, will@kernel.org, mark.rutland@arm.com, maz@kernel.org, broonie@kernel.org, debian-arm@lists.debian.org, Vagrant Cascadian , Riku Voipio , Steve McIntyre References: <20220701135322.3025321-1-ardb@kernel.org> MIME-Version: 1.0 In-Reply-To: <20220701135322.3025321-1-ardb@kernel.org> Organization: Wookware User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220713_185227_559018_C7700545 X-CRM114-Status: GOOD ( 16.83 ) 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: multipart/mixed; boundary="===============0520112697178920724==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============0520112697178920724== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="Ms5iOKSBOB9YS8zC" Content-Disposition: inline --Ms5iOKSBOB9YS8zC Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2022-07-01 15:53 +0200, Ard Biesheuvel wrote: > The 32-bit ARM kernel implements fixups on behalf of user space when > using LDM/STM or LDRD/STRD instructions on addresses that are not 32-bit > aligned. > This feature is one of the remaining impediments to being able to switch > to 64-bit kernels on 64-bit capable hardware running 32-bit user space, > so let's implement it for the arm64 compat layer as well. =20 > Note to cc'ees: if this is something you would like to see merged, > please indicate so. This stuff is unlikely to get in if there are no > users. Decent 32-bit arm hardware is thin on the ground these days. Debian still has some but it's getting old and flaky. Being able to build reliably on 64-bit hardware is important and useful. Unaligned accesses are much less of a problem than they used to be, but they can still happen, so having these fixups available is definitely a good thing. Debian runs its 32-bit buildds with alignment fixups turned on. It looks like the boxes still hit about 1 per day. We also do 32 bit builds on 64-bit kernels (in 32-bit userspaces) and it mostly works. We do have packages that fail on 64-bit kernels and have to be built on real 32-bit hardware, but I don't know how much of that would be fixed by this patch. Some, presumably. So yes, cheers for this. It is helpful in the real world (or at least it should be). Wookey --=20 Principal hats: Debian, Wookware, ARM http://wookware.org/ --Ms5iOKSBOB9YS8zC Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEER4nvI8Pe/wVWh5yq+4YyUahvnkcFAmLPdskACgkQ+4YyUahv nkcvBg/9G76VovQro8XfMnLlMRX+63IulXJOV8HtqM+dIweU9awz4pL099tmjdWe WtR5wSYrkP/7SzdBtOkJefem7rt3Gxnu3PVDqPHWnSvb48Xcey3G9xJJehpGpTRY kLHXHTNT+c+1zceJmI8oEF11i8D/AhlhhS8YwN55gSK8lwC99PnS834k+a2nklBO vvt5TARiDdMFQduFaadk2O0J1Zrt/5Z/nb/hNv7Oe/ZN9QTVe/GB2uy2il0+TJ/y Zr+KppkK++j/fNhZSsUZYxuwCoGoLC02Vr7U3b6qQkOLV8oi/CqczXaFv6Lrn9vH cJrQdwhyEInUcBcwEdPA4eVZw3YLQ3g+Z3VxnAKsl2yjD62JopRSvar2BUljtzcN 7MrRhz1bNavdP3GqOsnmywojPkp0gd9jLIZLZT1/7O2j5vVXuCOgJFm2LnRRl6Ne +RFJOVNXKdj9p/QdyTvWYJAJG54LxDKVe1q1gz+lltOfS9M7zr1/ZPLyBaB+oTaH Q+apnhRX2a8v+hwokQ7/QxMkGlpMQ3wCglJ0M/S/sh8/VDA4YIWxbqDdny/ldboS dCx5QDP/OTP0QtIk8Pxxan63JLk/8Ort4ObEa0vR1G/NmdY/XDvLiYrxvfWDzQnR PFgiXz/Ld58wDweyngLtB0MjekdqS5HlX5dfk9Ey2tyvHx7j0kI= =g1sR -----END PGP SIGNATURE----- --Ms5iOKSBOB9YS8zC-- --===============0520112697178920724== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============0520112697178920724==--