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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 521AEC43381 for ; Fri, 29 Mar 2019 15:39:41 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 20F942075E for ; Fri, 29 Mar 2019 15:39:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="msg5+Dn1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 20F942075E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Fm+15jiW1KkJrSWT8b2aHsHLLJKaG0XqtRLbCR6XAUc=; b=msg5+Dn1eG015W RaNJSU+wLAGt6nPgUrjVeATQhKY29saPslRYwDU9fwCDUAv2yuZS5uw9Qe7h2b7zsvY7Ta6c4VmBB FAUbomXC2aT3WzXs27cCV2cvq/j/Bya2OlCP3mldPQp8CDNgNI2SwvuGnwKWEd9A8Z4aF8L2AC75H wxX1oaDQw7wGYRx3pEcXhmVeMi0fyCC68Oxx0j5WBcWnK8gTUhN1VWZ5V815Z6sZIrMwxvauaB6X6 4vkWMW9+jgt1xphJ8tzeM1KHPHsLu6OlFrn3fCAEB/YkLGGTzhOlUfhSnhNRv6Q+KHxCZ59Mtysek IFVBj0+ElAIKnN5PoeAg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h9tbS-0008Qy-PP; Fri, 29 Mar 2019 15:39:34 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h9tbP-0008QZ-B1 for linux-arm-kernel@lists.infradead.org; Fri, 29 Mar 2019 15:39:32 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E10DE80D; Fri, 29 Mar 2019 08:39:30 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CF73E3F614; Fri, 29 Mar 2019 08:39:29 -0700 (PDT) Date: Fri, 29 Mar 2019 15:39:27 +0000 From: Dave Martin To: Andrew Murray Subject: Re: [PATCH v2 2/6] arm64: HWCAP: add support for AT_HWCAP2 Message-ID: <20190329153927.GE3567@e103592.cambridge.arm.com> References: <1550751657-30252-1-git-send-email-andrew.murray@arm.com> <1550751657-30252-3-git-send-email-andrew.murray@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1550751657-30252-3-git-send-email-andrew.murray@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190329_083931_382401_1F59D71D X-CRM114-Status: GOOD ( 13.99 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Szabolcs Nagy , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Feb 21, 2019 at 12:20:53PM +0000, Andrew Murray wrote: > As we will exhaust the first 32 bits of AT_HWCAP let's start > exposing AT_HWCAP2 to userspace to give us up to 64 caps. > > Whilst it's possible to use the remaining 32 bits of AT_HWCAP, we > prefer to expand into AT_HWCAP2 in order to provide a consistent > view to userspace between ILP32 and LP64. However internal to the > kernel we prefer to continue to use the full space of elf_hwcap. > > To reduce complexity and allow for future expansion, we now > represent hwcaps in the kernel as ordinals and use a > KERNEL_HWCAP_ prefix. This allows us to support automatic feature > based module loading for all our hwcaps. > > We introduce cpu_set_feature to set hwcaps which compliments the > existing cpu_have_feature helper. These helpers allow us to clean > up existing direct uses of elf_hwcap and reduce any future effort > required to move beyond 64 caps. > > For convenience we also introduce cpu_{have,set}_feature_name which > makes use of the cpu_feature macro to allow providing a hwcap name > without a {KERNEL_}HWCAP_ prefix. [...] Btw, this series will also need to update Documentation/elf_hwcaps.txt. (You may have been planning to do that anyway, but I just realised.) Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel