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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3FED1EB64DA for ; Thu, 20 Jul 2023 12:27:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231197AbjGTM1X (ORCPT ); Thu, 20 Jul 2023 08:27:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230386AbjGTM1T (ORCPT ); Thu, 20 Jul 2023 08:27:19 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1EE1F2118; Thu, 20 Jul 2023 05:27:18 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id ABB0F618F6; Thu, 20 Jul 2023 12:27:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CB6CAC433C8; Thu, 20 Jul 2023 12:27:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689856036; bh=rCw+psKLDBdl6kAXIJPY9IcEhZY5IxhHwvg4KUYy27Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BwiRNKVJdr15gmyYf87c5qkAeJKVgK0bUhpYNBH1JoM8PiqO/jE0lKC7Dha56w0BT 7O/vwi9WBffNUurAE/FZjy7XJUz2CFkFxvVB7vCi6Ru6h6KIU083RJOIryIfENkD1X oTENDWIdJqSXUAPOfCcYOIf/NGXgzL/80xC+2m1uOmTieNUgd9F7ACJib/Zssmi7kJ h8IWNcPMAhii51lmlhTmMjHATZ9KWJgeQ7ghBT/98FD0E6coqekAxPi+iTbkKn/6IH LI7B5Qlh4ewNKw5JkkAM1YGH45chzb7Sy41C856SadZ3c4y6onctYse05VbAblsj7m JvR4b6hrEFSTA== Date: Thu, 20 Jul 2023 13:27:10 +0100 From: Mark Brown To: Will Deacon Cc: Catalin Marinas , Shuah Khan , David Spickett , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/3] arm64/fpsimd: Ensure SME storage is allocated after SVE VL changes Message-ID: <3ce4fc14-bd43-47e9-aa37-59bb3cd5d051@sirena.org.uk> References: <20230713-arm64-fix-sve-sme-vl-change-v1-0-129dd8611413@kernel.org> <20230713-arm64-fix-sve-sme-vl-change-v1-1-129dd8611413@kernel.org> <20230720105235.GD11034@willie-the-truck> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="CyMXBdFoH12etnuE" Content-Disposition: inline In-Reply-To: <20230720105235.GD11034@willie-the-truck> X-Cookie: Ginger snap. Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --CyMXBdFoH12etnuE Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Jul 20, 2023 at 11:52:36AM +0100, Will Deacon wrote: > On Thu, Jul 13, 2023 at 09:06:04PM +0100, Mark Brown wrote: > > Since the ABI does not specify that changing the SVE vector length disturbs > > SME state, and since SVE code may not be aware of SME code in the process, > > we shouldn't simply discard any ZA state. Instead immediately reallocate > > the storage for SVE if SME is active, and disable SME if we change the SVE > > vector length while there is no SME state active. > What is the advantage of keep the old behaviour in this case? In other > words, if it's acceptable to reallocate the state when SME is active, why > not just reallocate in all cases? It was minimising the changes to the status quo given how attached people often are to these things. --CyMXBdFoH12etnuE Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmS5KB4ACgkQJNaLcl1U h9C+0gf/fQxZuh51kIYByTPW3QLeYr1gzvXo8eFWKQxVOYg96BpcLaqbrocw6ZLg E0VA1/CrGB56VUq99z4VY0JUrqFoupiFJE5M5MihIAUi/0PPH9LsvzvuXuIAnrK4 CmqsOfSQTbsXhntG34dq3UkcK7VZlbK4iSZsaKig3BLtIWHBVJ1WvLpnxEkVu0Mv +qJM4GDgPeIXRKiMcxT6+Gd96Vza5VFUemOFSO9BGW5XzQE7Ix+NpT99XvE0MtwJ mTVS7V3g0F+19U08hExwfgrKS1ybUONPOqncDhwLdghsLFFOeW8WI1ttxw26afX8 UO1YvtblScSAt6Aex+N4yBujBbHMaA== =NOme -----END PGP SIGNATURE----- --CyMXBdFoH12etnuE--