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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DFEA6C433FE for ; Mon, 14 Feb 2022 13:58:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354748AbiBNN6v (ORCPT ); Mon, 14 Feb 2022 08:58:51 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:38580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353936AbiBNN6t (ORCPT ); Mon, 14 Feb 2022 08:58:49 -0500 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 87095CFD; Mon, 14 Feb 2022 05:58:41 -0800 (PST) Received: by verein.lst.de (Postfix, from userid 2407) id C2B0468BEB; Mon, 14 Feb 2022 14:58:34 +0100 (CET) Date: Mon, 14 Feb 2022 14:58:34 +0100 From: Christoph Hellwig To: Tianyu Lan Cc: Christoph Hellwig , kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, hch@infradead.org, m.szyprowski@samsung.com, robin.murphy@arm.com, michael.h.kelley@microsoft.com, Tianyu Lan , iommu@lists.linux-foundation.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, vkuznets@redhat.com, brijesh.singh@amd.com, konrad.wilk@oracle.com, parri.andrea@gmail.com, thomas.lendacky@amd.com Subject: Re: [PATCH V2 1/2] Swiotlb: Add swiotlb_alloc_from_low_pages switch Message-ID: <20220214135834.GA30150@lst.de> References: <20220209122302.213882-1-ltykernel@gmail.com> <20220209122302.213882-2-ltykernel@gmail.com> <20220214081919.GA18337@lst.de> <4f433f07-05be-f81f-43e8-55c3f1af23b3@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4f433f07-05be-f81f-43e8-55c3f1af23b3@gmail.com> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 14, 2022 at 07:28:40PM +0800, Tianyu Lan wrote: > On 2/14/2022 4:19 PM, Christoph Hellwig wrote: >> Adding a function to set the flag doesn't really change much. As Robin >> pointed out last time you should fine a way to just call >> swiotlb_init_with_tbl directly with the memory allocated the way you >> like it. Or given that we have quite a few of these trusted hypervisor >> schemes maybe add an argument to swiotlb_init that specifies how to >> allocate the memory. > > Thanks for your suggestion. I will try the first approach first approach. Take a look at the SWIOTLB_ANY flag in this WIP branch: http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/swiotlb-init-cleanup That being said I'm not sure that either this flag or the existing powerpc code iѕ actually the right thing to do. We still need the 4G limited buffer to support devices with addressing limitations. So I think we need an additional io_tlb_mem instance for the devices without addressing limitations instead.