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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B0EC8C433EF for ; Fri, 4 Mar 2022 16:35:09 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4K9D3Z5SNLz30NW for ; Sat, 5 Mar 2022 03:35:06 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lst.de (client-ip=213.95.11.211; helo=verein.lst.de; envelope-from=hch@lst.de; receiver=) Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4K9D3436SXz2x9d for ; Sat, 5 Mar 2022 03:34:38 +1100 (AEDT) Received: by verein.lst.de (Postfix, from userid 2407) id E2BFF68AFE; Fri, 4 Mar 2022 17:34:30 +0100 (CET) Date: Fri, 4 Mar 2022 17:34:30 +0100 From: Christoph Hellwig To: Stefano Stabellini Subject: Re: [PATCH 11/12] swiotlb: merge swiotlb-xen initialization into swiotlb Message-ID: <20220304163430.GA12317@lst.de> References: <20220301105311.885699-1-hch@lst.de> <20220301105311.885699-12-hch@lst.de> <20220302081500.GB23075@lst.de> <20220303105931.GA15137@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-hyperv@vger.kernel.org, x86@kernel.org, linux-ia64@vger.kernel.org, linux-pci@vger.kernel.org, linux-riscv@lists.infradead.org, Christoph Hellwig , linux-s390@vger.kernel.org, Joerg Roedel , Konrad Rzeszutek Wilk , tboot-devel@lists.sourceforge.net, xen-devel@lists.xenproject.org, David Woodhouse , Tom Lendacky , Anshuman Khandual , Boris Ostrovsky , linux-arm-kernel@lists.infradead.org, Juergen Gross , Robin Murphy , linux-mips@vger.kernel.org, iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, Lu Baolu Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Mar 03, 2022 at 02:49:29PM -0800, Stefano Stabellini wrote: > On Thu, 3 Mar 2022, Christoph Hellwig wrote: > > On Wed, Mar 02, 2022 at 05:25:10PM -0800, Stefano Stabellini wrote: > > > Thinking more about it we actually need to drop the xen_initial_domain() > > > check otherwise some cases won't be functional (Dom0 not 1:1 mapped, or > > > DomU 1:1 mapped). > > > > Hmm, but that would be the case even before this series, right? > > Before this series we only have the xen_swiotlb_detect() check in > xen_mm_init, we don't have a second xen_initial_domain() check. > > The issue is that this series is adding one more xen_initial_domain() > check in xen_mm_init. In current mainline xen_mm_init calls xen_swiotlb_init unconditionally. But xen_swiotlb_init then calls xen_swiotlb_fixup after allocating the memory, which in turn calls xen_create_contiguous_region. xen_create_contiguous_region fails with -EINVAL for the !xen_initial_domain() and thus caues xen_swiotlb_fixup and xen_swiotlb_init to unwind and return -EINVAL. So as far as I can tell there is no change in behavior, but maybe I'm missing something subtle?