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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 95EE3C4321A for ; Sat, 29 Jun 2019 13:21:53 +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 658BB2054F for ; Sat, 29 Jun 2019 13:21:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="OUGaEUXr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 658BB2054F 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=cD4+2q10wvDHH1E3Sn/PryMVLo/xY71ON2qs1qO1vko=; b=OUGaEUXr3hvS9Y BbDhHFx4wRTFAR1MyqU1ROzUVosBOkTNMZglY1L0sEiVlPZS+dDVDfLoXJt0RPSNfQrVLjNDbNsSs u+PMCQCM2Mfrtqk5jbslubOL+OF5JxB3rf5FNGHSg68SFzEfRL6p/5ayS/Pgtad+QL+9VyU7e2Bii yHzo8zek2PsrHDXYk62Ihtz1I812D/nTAeZiiYahKI0WE/+CZ12da49Ka6kz7T92dqfCZ6UhTp0kH dHtHcPERLQN8dLq/SnQr6YlEm27ZTUJtxOWD/UIzGmTwlPzrQ8hY7JmMoDe9gJ7cXe0J44W258nMW +E75A94yZEXw/sxVxUJw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hhDIY-0004hX-45; Sat, 29 Jun 2019 13:21:46 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hhDIV-0004gM-A7 for linux-arm-kernel@lists.infradead.org; Sat, 29 Jun 2019 13:21:44 +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 00543344; Sat, 29 Jun 2019 06:21:36 -0700 (PDT) Received: from mbp (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3564D3F718; Sat, 29 Jun 2019 06:21:35 -0700 (PDT) Date: Sat, 29 Jun 2019 14:21:29 +0100 From: Catalin Marinas To: Mark Brown Subject: Re: [PATCH v2] arm64: Add initial support for E0PD Message-ID: <20190629132128.fdv4f23sjpsaxypg@mbp> References: <20190627141532.6452-1-broonie@kernel.org> <20190628110430.ffdqy5on3retyr42@willie-the-truck> <20190628123040.GG5379@sirena.org.uk> <20190628163642.GB56463@arrakis.emea.arm.com> <20190628173920.GA2793@sirena.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190628173920.GA2793@sirena.org.uk> User-Agent: NeoMutt/20170113 (1.7.2) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190629_062143_397230_10CDD2C0 X-CRM114-Status: GOOD ( 16.64 ) 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: 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 Hi Mark, On Fri, Jun 28, 2019 at 06:39:20PM +0100, Mark Brown wrote: > On Fri, Jun 28, 2019 at 05:36:42PM +0100, Catalin Marinas wrote: > > On Fri, Jun 28, 2019 at 01:30:40PM +0100, Mark Brown wrote: > > > > It's largely on the general theory that it's better to carry less out of > > > tree code - there's less diff to manage, less chance of collisions with > > > other work (in either direction), and less pending review to worry about. > > > So long as something represents forward progress I tend to work on the > > > basis of why not rather than why. > > > A reason is that once we add the support for disabling kpti based on > > the E0PD feature, this patch may turn out to be slightly different (for > > example, you may add a common has_e0pd() check that is called from > > both unmap_kernel_at_el0() and the E0PD arm64_features[] entry). Given > > Hrm, I don't really get that - incremental patches can always be done > (indeed they're often really helpful for people trying to understand how > the code got to be the way it is). Sorry, I wasn't clear enough. I'm perfectly fine to incremental patches and encourage them as part of a series achieving an end goal. Here the end goal (and the reason behind this architecture feature) is to be able to safely disable KPTI in favour of a hardware-based mitigation. Your one-patch series does not achieve this yet, so I suggest we don't merge this until we have the other part of the series. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel