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 57116EE49AA for ; Tue, 22 Aug 2023 17:01:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237962AbjHVRBh (ORCPT ); Tue, 22 Aug 2023 13:01:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35540 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237969AbjHVRBg (ORCPT ); Tue, 22 Aug 2023 13:01:36 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 71DECFB; Tue, 22 Aug 2023 10:01:35 -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 0B93C643F3; Tue, 22 Aug 2023 17:01:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74E4BC433C7; Tue, 22 Aug 2023 17:01:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692723694; bh=4CwJzH4TL2Y8EXaFoTYYQXYVEx5uhhyOhGKEBL5M5a4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nwIELk0L965ZZxRQU/I6AfIxI41pPfoJ/8ilmpqMMDxttWnkizigjluGn+Ari53wx MqNyiNJuURRYl2rCuLNJJ2Cs85l4nwq7Q2vWycN3a3XFaBaWvpt/KvtYd4TWJtE93y 2mhcqEGqeiz2SkybCYJmTOdlsX5/UNDCZXZ+F5YxZ6vS1R+LOWxtY7m0pc+kMGPPlJ kPp/83wuyHdo3Irho6uo8xb6TPcAKTt8iUzDXu8bbnYEB9weodOZjJ9UCKfJORCNeV gnjnzeyg+Tps+7sTo22OVIrcM6LgodrBWVlbjMG9YcUoS05XXyscb+z/gcliAOGlOk ceFShSQCdJEsg== Date: Tue, 22 Aug 2023 18:01:25 +0100 From: Mark Brown To: Catalin Marinas Cc: Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Kees Cook , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH v4 18/36] arm64/gcs: Context switch GCS state for EL0 Message-ID: <699c1105-df8e-4a08-ae6c-8c01a13e4a3d@sirena.org.uk> References: <20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org> <20230807-arm64-gcs-v4-18-68cfa37f9069@kernel.org> <28a61b5f-db65-427e-8e92-60dd61549da5@sirena.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="/y5R8A5W/qG63MLx" Content-Disposition: inline In-Reply-To: X-Cookie: MIT: Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org --/y5R8A5W/qG63MLx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Tue, Aug 22, 2023 at 05:34:38PM +0100, Catalin Marinas wrote: > On Wed, Aug 16, 2023 at 07:15:53PM +0100, Mark Brown wrote: > > Right, it's for the GCS memory rather than the registers. I'm fairly > > sure it's excessive but but was erring on the side of caution until I > > have convinced myself that the interactions between GCS barriers and > > regular barriers were doing the right thing, until we have physical > > implementations to contend with I'd guess the practical impact will be > > minimal. > Well, I'd say either we are clear about why it's (not) needed or we ask > the architects to clarify the spec. I haven't checked your latest > series but in principle I don't like adding barriers just because we are > not sure they are needed (and I don't think having hardware eventually > changes this). I should probably also mention that another part of my thinking was that when we implement GCS for EL1 we'll need to ensure that everything is synced during the pivot of the EL1 GCS (each EL needs an independent GCS). We won't be able to rely on having an ERET there so it's going to have more stringent requirements, I was partly punting to think things through fully there. --/y5R8A5W/qG63MLx Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmTk6eQACgkQJNaLcl1U h9A05Qf/V5pH2tcF7cng/WQnlzNdmdQF2NZIRZuZVVzKe1JQ/d5SGT8sP/2ifM6m wN2P+4yqnMpjdMltFNtMpcnsMQDx7U6kGEmfdBOpr7tmr3dLxpE9snGGTiwRWUtu Th+Jz7B9omQ+w4wFZLCcZZtpiQcjpDwzqiW8ubZdoqdvyGOSkRO9xx6P47d07ter dmAEKsDiEQbU/2eFycrJRA85aSwx6Kv1tAC3ZPjigcmFnCGqomM3VzJ0QZNCsMTz SiUY5GKoO9gk9JPNd4c57jhzWikGGoFFzivLbal/hPfr8MzeIIrVCR7Jxm4ZNRkX zs3fDy9ePEheBAThiikuE6F7aPriRw== =VUaf -----END PGP SIGNATURE----- --/y5R8A5W/qG63MLx--