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 55E1BC433EF for ; Wed, 6 Jul 2022 10:17:15 +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-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:Cc:To:From :Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=fbnaMMGSD+BdfU5YZBCf7rQc07eY2IyH1zFSWejphBc=; b=ot/rw4mXvWZLrUq9IzP6JnSDOE Nn6FLDupbZ8Ie+C/4I4jr6J328O3X3RjH2yxEpEL90gpe18o5gsqepCq/vyEyYBKgFP9+oEVNmwKB WH7VY+Hg5pX3h+pOG8ULmMXAnmxNh8IxIeb792alc/kUFRQhpF3bM/F8HktUoSamGoouqknkkT4ko 9whfI3UvaNEgKnQulFn2yAe/GsGndaS3J8sLJK4ZJ+gEbfLs5k7GDRBNyFpsy9JCGPWQ6XdN48X/B Eslv7msktG3rOtkO9UUznmhdhzVrd9JQb0cDBRwOBaUwXDUX2iW00UZzpe13jgPYxbJN/33GENC9b 8+/9xXEQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o924U-008Hvp-Hd; Wed, 06 Jul 2022 10:15:51 +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 1o91xq-008BWw-Tw for linux-arm-kernel@lists.infradead.org; Wed, 06 Jul 2022 10:09:00 +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 618DD61D90; Wed, 6 Jul 2022 10:08:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0FDEC3411C; Wed, 6 Jul 2022 10:08:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1657102137; bh=FJgiZCVMI2EgnQUx7KPaSLrSnoyyBRU5cNVhPhi3vQg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NdH8Ej7ZvMRH9ZlXq/A5UD/S211qiZvwfItFusROGLF1HmTwgdCa6Ns3cqNp8LmJN FnuGGy74fCyRgSwS69IUaH8lNDnpLZJ2pADzVsALnsbFSpNDnIqtpFbCWAvSOy841W JpYy60CMPax5V3xqoyLQYAMUsZXWXZiVrCSsEzxoSKsLh+W3ugto7a3h/4utnaM811 K4zKGMFSwTuh+llMqpjqOVy/osmmo0OvVJ+BFk48k1da1yaE6wtcmoHPhwCbBz7e4p TIimEY5YuhjwpTh57EaBnwCWK9nq78HmeXrAaMjpfw9iXHUjzRh97k6ekshSypQUOU qg6rI+k3B+fww== Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1o91xn-005bGH-Gl; Wed, 06 Jul 2022 11:08:55 +0100 MIME-Version: 1.0 Date: Wed, 06 Jul 2022 11:08:55 +0100 From: Marc Zyngier To: Mark Brown Cc: Catalin Marinas , Will Deacon , Eric Biederman , Kees Cook , Suzuki K Poulose , Szabolcs Nagy , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 0/4] arm64: Add AT_HWCAP3 In-Reply-To: References: <20220620125451.653507-1-broonie@kernel.org> User-Agent: Roundcube Webmail/1.4.13 Message-ID: <933dd93bedf07883a62f59805dc28ca9@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: broonie@kernel.org, catalin.marinas@arm.com, will@kernel.org, ebiederm@xmission.com, keescook@chromium.org, suzuki.poulose@arm.com, szabolcs.nagy@arm.com, linux-arm-kernel@lists.infradead.org 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-20220706_030859_130088_AA8F161F X-CRM114-Status: GOOD ( 19.37 ) 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2022-07-05 18:53, Mark Brown wrote: > On Mon, Jun 20, 2022 at 01:54:47PM +0100, Mark Brown wrote: >> Currently for arm64 we expose hwcaps to userspace using the low 32 >> bits >> of AT_HWCAP and AT_HWCAP2. Due to the ever expanding capabilties of >> the >> architecture we have now allocated all the available bits in this >> scheme >> so we need to expand, either using the higher bits or adding a new >> AT_HWCAP3. Discussions with glibc developers suggested that AT_HWCAP3 >> would be cleaner for them so the series adopts that approach. > > This discussion appears to have ground to a halt. Szabolcs prefers > AT_HWCAP3, Catalin using the high bits of AT_HWCAP2 for now and nobody > else said anything. I don't have strong preferences either way but > wonder if it's worth defining AT_HWCAP3 even if we start allocating > more > bits from AT_HWCAP2 so that it's got more time to percolate through > libcs and so on before it's actually needed. > > What should we do here? I really don't like the idea of adding a new HWCAP when we still have free bits lying around. We should use that first, and only add HWCAP3 once we are at (or close enough to) the limit. That's assuming that there is no breakage with using these spare bits. If something is at risk, I'd be good to spell it out. M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel