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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 6D93BC43331 for ; Thu, 2 Apr 2020 12:18:01 +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 394DA206F8 for ; Thu, 2 Apr 2020 12:18:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="PQRSUYpB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 394DA206F8 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=njM89rusRylSCL6CclJQuebmZ871qGk/5au+0GlllWU=; b=PQRSUYpB8OSprv 7TavavOezimjos4FwZD6dGpYxVPxbHaiRVTEsSmg20SkLiIiZNX5dAGcxPlnb5FswirqJSWSPSYeH VR0G0uXh6Iyk/ysGcnRx0RTtrOsQ21SXPaBf4PUqHzFKaLIBNyS2ho0rQPxrNzXQmmZz8dSm66MvH 74GDsJZ8hpytzo7lOmSBANdkKvywSCNyluEHYmpTAR2oNdd01Gx663/15dOin0Cv0AbvhuxRpDzoL oBCtMtKbyLQwrSPd/AJyzvOk49FLE2RUSQq6V1gclBUq0kh0tNrdoIQV/LMF6x5/wsWva5iqAyS9j G8Gw3PgcIKwaxs0Bb4gw==; 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 1jJynI-0000VR-3P; Thu, 02 Apr 2020 12:18:00 +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 1jJynF-0000Uk-3b for linux-arm-kernel@lists.infradead.org; Thu, 02 Apr 2020 12:17:58 +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 7B4151045; Thu, 2 Apr 2020 05:17:54 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.31.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0D5E53F68F; Thu, 2 Apr 2020 05:17:52 -0700 (PDT) Date: Thu, 2 Apr 2020 13:17:45 +0100 From: Mark Rutland To: Catalin Marinas Subject: Re: [RFC PATCH] arm64: remove CONFIG_DEBUG_ALIGN_RODATA feature Message-ID: <20200402121745.GA29906@C02TD0UTHF1T.local> References: <20200329141258.31172-1-ardb@kernel.org> <20200330135121.GD10633@willie-the-truck> <20200330140441.GE10633@willie-the-truck> <20200330142805.GA11312@willie-the-truck> <20200402113033.GD21087@mbp> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200402113033.GD21087@mbp> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200402_051757_191002_5DA9A462 X-CRM114-Status: GOOD ( 12.56 ) 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 , Ard Biesheuvel , Linux ARM , kernel-hardening@lists.openwall.com 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, Apr 02, 2020 at 12:30:33PM +0100, Catalin Marinas wrote: > On Mon, Mar 30, 2020 at 04:32:31PM +0200, Ard Biesheuvel wrote: > > Could we make this a runtime thing? E.g., remap the entire linear > > region down to pages under stop_machine() the first time we probe a > > device that uses non-coherent DMA? > > That could be pretty expensive at run-time. With the ARMv8.4-TTRem > feature, I wonder whether we could do this lazily when allocating > non-coherent DMA buffers. It's worth noting that ARMv8.4-TTRem is optional and the "level 1" and "level 2" behaviours still allows non-fatal faults to be taken while nT is set (or until you perform the TLB invalidation). We can only safely use it where we could use a full BBM sequence today. Effectively TTRem is an optimized, where the CPU *might* be able to use entries during the break stage, but is not guaranteed to do so. Thanksm Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel