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=-8.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 43B8DC11F67 for ; Tue, 6 Jul 2021 19:14:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2DA5F600D3 for ; Tue, 6 Jul 2021 19:14:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231845AbhGFTRC (ORCPT ); Tue, 6 Jul 2021 15:17:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:51076 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231727AbhGFTRA (ORCPT ); Tue, 6 Jul 2021 15:17:00 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0B79260FEE; Tue, 6 Jul 2021 19:14:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625598861; bh=QlBKfCu996qP5JenUg1J68Cu2xyoSjshlo1u0WQ5l4Q=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=TU5TtD5UIfY0r+aXmb18IJawcVy9481TeWFSQOFYJdeGslFF5REp8bH73BojUcAOS WlHc4LPuYi7chvxRgoEbHiUmVBJCPC7C5tF6pdGMxY91712ZIHIFWEljUXECaizwR+ koaeta5RgZiHx0Sss+0r3QJAYmQBlDDtVdoZp0FeXJcOVflgaIqK1qCkplXl/uW0BS LCRRvULfQJWTmzcODhL8YcjXYnyWkDWBHwYJN74M0CyF9fd7kjSS4G13Z+1zJxm7S+ SxqHpxzj/Vqq6tNxTCJBSiyuyZK+lbgOtwblLLeGRCpsIt4FpxqITodwMfqKGzStS2 aVPLPXphc2cDw== Subject: Re: [PATCH v15 06/12] swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing To: Will Deacon , Robin Murphy Cc: Christoph Hellwig , heikki.krogerus@linux.intel.com, thomas.hellstrom@linux.intel.com, peterz@infradead.org, benh@kernel.crashing.org, joonas.lahtinen@linux.intel.com, dri-devel@lists.freedesktop.org, chris@chris-wilson.co.uk, grant.likely@arm.com, paulus@samba.org, Frank Rowand , mingo@kernel.org, Stefano Stabellini , Saravana Kannan , mpe@ellerman.id.au, "Rafael J . Wysocki" , Bartosz Golaszewski , bskeggs@redhat.com, linux-pci@vger.kernel.org, xen-devel@lists.xenproject.org, Thierry Reding , intel-gfx@lists.freedesktop.org, matthew.auld@intel.com, linux-devicetree , Jianxiong Gao , Daniel Vetter , Konrad Rzeszutek Wilk , maarten.lankhorst@linux.intel.com, airlied@linux.ie, Dan Williams , linuxppc-dev@lists.ozlabs.org, jani.nikula@linux.intel.com, Rob Herring , rodrigo.vivi@intel.com, Bjorn Helgaas , Claire Chang , boris.ostrovsky@oracle.com, Andy Shevchenko , jgross@suse.com, Nicolas Boichat , Greg KH , Randy Dunlap , Qian Cai , lkml , "list@263.net:IOMMU DRIVERS" , Jim Quinlan , xypron.glpk@gmx.de, Tom Lendacky , bauerman@linux.ibm.com References: <20210702135856.GB11132@willie-the-truck> <0f7bd903-e309-94a0-21d7-f0e8e9546018@arm.com> <20210705190352.GA19461@willie-the-truck> <20210706044848.GA13640@lst.de> <20210706132422.GA20327@willie-the-truck> <20210706140513.GA26498@lst.de> <20210706170657.GD20750@willie-the-truck> From: Nathan Chancellor Message-ID: Date: Tue, 6 Jul 2021 12:14:16 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210706170657.GD20750@willie-the-truck> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Will and Robin, On 7/6/2021 10:06 AM, Will Deacon wrote: > On Tue, Jul 06, 2021 at 04:39:11PM +0100, Robin Murphy wrote: >> On 2021-07-06 15:05, Christoph Hellwig wrote: >>> On Tue, Jul 06, 2021 at 03:01:04PM +0100, Robin Murphy wrote: >>>> FWIW I was pondering the question of whether to do something along those >>>> lines or just scrap the default assignment entirely, so since I hadn't got >>>> round to saying that I've gone ahead and hacked up the alternative >>>> (similarly untested) for comparison :) >>>> >>>> TBH I'm still not sure which one I prefer... >>> >>> Claire did implement something like your suggestion originally, but >>> I don't really like it as it doesn't scale for adding multiple global >>> pools, e.g. for the 64-bit addressable one for the various encrypted >>> secure guest schemes. >> >> Ah yes, that had slipped my mind, and it's a fair point indeed. Since we're >> not concerned with a minimal fix for backports anyway I'm more than happy to >> focus on Will's approach. Another thing is that that looks to take us a >> quiet step closer to the possibility of dynamically resizing a SWIOTLB pool, >> which is something that some of the hypervisor protection schemes looking to >> build on top of this series may want to explore at some point. > > Ok, I'll split that nasty diff I posted up into a reviewable series and we > can take it from there. For what it's worth, I attempted to boot Will's diff on top of Konrad's devel/for-linus-5.14 and it did not work; in fact, I got no output on my monitor period, even with earlyprintk=, and I do not think this machine has a serial console. Robin's fix does work, it survived ten reboots with no issues getting to X and I do not see the KASAN and slub debug messages anymore but I understand that this is not the preferred solution it seems (although Konrad did want to know if it works). I am happy to test any further patches or follow ups as needed, just keep me on CC. Cheers, Nathan