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,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 0A30AC47254 for ; Tue, 5 May 2020 10:44:13 +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 D1AB2206B9 for ; Tue, 5 May 2020 10:44:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="GhcgRn4r"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="umfSfVmA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D1AB2206B9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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=U+LeMCwly+yOGwqPc9bU+7Q+WvDJesKXKuzx9M0P7U8=; b=GhcgRn4ra20d6o lpH6zRkbiQauuBICJo4sdM/mmOVecq9pGOB0W7BdCHBh/3NBCYX7eQvUoQfsIEe1oKboLKq9yj5Z0 3z7MFwUzYkPsyPTS/g3tbQxATI7ci/wYkU2Vnupf9Q5hInN0QmqbVMtM1MwdTI6looSrf8wcDnOa8 yBp1iaPS7AHwBlOUI2QRk75BhemUF58s2GIKiCOZuntQkOZebcZ8UxApLv/3lp7zkZMj6KXsD+Amx 5b9e+gakbAaWlxq7TYhtyzXLhmGjv0MqUVS25XBJC4PDsrdGa8jxKcXrSQRTvkjPnMb4db6s6NUTO lp6gbVSqQzo/MLfRXJnA==; 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 1jVv3c-0007Lu-G8; Tue, 05 May 2020 10:44:12 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jVv3a-0007LS-6U for linux-arm-kernel@lists.infradead.org; Tue, 05 May 2020 10:44:11 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E5E07206A5; Tue, 5 May 2020 10:44:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588675449; bh=GEhF2tEU4XkWefXPE5udcRA2Y0YzSMAJ2YekTBmZRN8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=umfSfVmAzQRn1jZ3bKYhL7bz38WXiQuVIirVZy0mTX6WcttQ58u31IvMAtuwooHlI zAg67Rt+mmAcMu69MDpIYRff/zJipCTQzdMaBVWDy4jcVv2gFlg5jJGS3SGHf7E1rl 7ZzUXD/6ZKX4GNHL37htRHoduxFXkj5zNfDqSsKA= Date: Tue, 5 May 2020 11:44:06 +0100 From: Will Deacon To: Ard Biesheuvel Subject: Re: [RFC PATCH] arm64: remove CONFIG_DEBUG_ALIGN_RODATA feature Message-ID: <20200505104404.GB19710@willie-the-truck> 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: 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-20200505_034410_256670_7A286D0B X-CRM114-Status: GOOD ( 16.63 ) 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 , Catalin Marinas , 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 Fri, Apr 03, 2020 at 10:58:51AM +0200, Ard Biesheuvel wrote: > On Thu, 2 Apr 2020 at 13:30, Catalin Marinas wrote: > > On Mon, Mar 30, 2020 at 04:32:31PM +0200, Ard Biesheuvel wrote: > > > On Mon, 30 Mar 2020 at 16:28, Will Deacon wrote: > > > > Fair enough, but I'd still like to see some numbers. If they're compelling, > > > > then we could explore something like CONFIG_OF_DMA_DEFAULT_COHERENT, but > > > > that doesn't really help the kconfig maze :( > > > > I'd prefer not to have a config option, we could easily break single > > Image at some point. > > > > > 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. > > > > (I still hope there isn't a problem at all with this mismatch ;)). > > > > Now that we have the pieces to easily remap the linear region down to > pages, and [apparently] some generic infrastructure to manage the > linear aliases, the only downside is the alleged performance hit > resulting from increased TLB pressure. This is obviously highly > micro-architecture dependent, but with Xgene1 and ThunderX1 out of the > picture, I wonder if the tradeoffs are different now. Maybe by now, we > should just suck it up (Note that we had no complaints afaik regarding > the fact that we map the linear map down to pages by default now) I'd be in favour of that fwiw. Catalin -- did you get anything back from the architects about the cache hit behaviour? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel