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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 02D2DC33CB1 for ; Thu, 16 Jan 2020 11:02:59 +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 C0EC420730 for ; Thu, 16 Jan 2020 11:02:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="W2jATqe3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0EC420730 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=Ai1XQGcK4Lc36uFjDjSvksN24naw2uZtEV2NtaZPJxY=; b=W2jATqe3oS7RzP JY1DOjLq0m9ypGHHfZZX6bgJuYX9vhHEEQCUq0kMpITDIC3GYg4SmLdjxFWsxNNQ0wBF3TXtAs4Ma F22Ilc0lQvMKe5ZgjlRaz3UZAnvv7Dim0w4pPYPD8v6ytsVvIJMMYDuG7FJ/Nv41LvWjT/2q1YTPN NXXQdpRztMSbfWGA2v1WilqKUfczVUfxVXvXgzvtVhkPaG+W3r6FUJq9b5cVjL6Zb3oGLxs2FfJDv OxHQ4ih6tU+7pGF/5xAdE53HzTzAEHpqufnoqQb7DRiAD9+zv+6NRwFraoAlVqzqqtoKSlXCKtsZK Sz/Nrq5YA5pVyhF/Clow==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1is2vS-0001gu-FX; Thu, 16 Jan 2020 11:02:58 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1is2vK-0001fU-BD for linux-arm-kernel@lists.infradead.org; Thu, 16 Jan 2020 11:02:56 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7C40331B; Thu, 16 Jan 2020 03:02:48 -0800 (PST) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.197.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 940A13F534; Thu, 16 Jan 2020 03:02:47 -0800 (PST) Date: Thu, 16 Jan 2020 11:02:45 +0000 From: Catalin Marinas To: Richard Henderson Subject: Re: [PATCH v10 1/3] arm64: Implement archrandom.h for ARMv8.5-RNG Message-ID: <20200116110245.GB10277@arrakis.emea.arm.com> References: <20200110122341.8445-1-broonie@kernel.org> <20200110122341.8445-2-broonie@kernel.org> <20200114174432.GG2579@willie-the-truck> <20200115091651.GB21692@willie-the-truck> <20200115110720.GG3897@sirena.org.uk> <20200115142611.GC3429@arrakis.emea.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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-20200116_030250_426705_CD14377E X-CRM114-Status: GOOD ( 16.75 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Mark Brown , Will Deacon , linux-arm-kernel , Ard Biesheuvel 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 Wed, Jan 15, 2020 at 02:23:39PM -1000, Richard Henderson wrote: > On 1/15/20 4:26 AM, Catalin Marinas wrote: > > On Wed, Jan 15, 2020 at 11:07:20AM +0000, Mark Brown wrote: > >> On Wed, Jan 15, 2020 at 10:24:21AM +0100, Ard Biesheuvel wrote: > >>> On Wed, 15 Jan 2020 at 10:16, Will Deacon wrote: > >> > >>>> I see your argument, but I was just going on the side of consistency because > >>>> we're continuing to expose other features as HWCAPs when the capability is > >>>> just a proxy for the cpuid field. I was in favour of stopping the addition > >>>> of such HWCAPs years ago, but I couldn't convince Catalin ;) > >> > >>>> The way I see it, we'll soon run out of HWCAP2 bits and then we'll have > >>>> our hand forced. > >> > >>> I don't have a strong opinion either way. > >> > >> Me either, or at least not enough to object to doing it - Will? > >> Catalin? > > > > Until the ifunc resolver can work with CPUID, I think we should keep > > adding HWCAPn bits. We can revisit this with the toolchain people before > > introducing HWCAP3. > > Why would the ifunc resolver not be able to use HWCAP_CPUID? It can indeed check the HWCAP_CPUID but I haven't seen any plans to implement the next part, actual use of an MRS instruction to read the corresponding ID_AA64* regs. This MRS emulation was requested by (some of) the toolchain people, even the architecture gained a feature to simplify the emulation, but followed by complete silence from the toolchain folk. > That said, speaking as a toolchain guy, you should conserve HWCAP2 bits so > that, by preference, you do not need to introduce AT_HWCAP3. Or at least delay > adding it. We still have some time before AT_HWCAP3. Also, we have 32-bit spare in both HWCAP and HWCAP2 which we can use. IIRC we didn't go into the top 32-bit of HWCAP because we were still debating whether ILP32 makes sense (and now I'm 100% convinced it doesn't ;)). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel