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 847CBECAAA1 for ; Fri, 9 Sep 2022 14:47:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232211AbiIIOrb (ORCPT ); Fri, 9 Sep 2022 10:47:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232216AbiIIOr2 (ORCPT ); Fri, 9 Sep 2022 10:47:28 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 519711282C5; Fri, 9 Sep 2022 07:47:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=MKCJGQImC5rNFm8xlhIZtRyfnfFLIWT7YCm6bd8rOy4=; b=V7t/u3J6Ot1dGFxPwqjtFrioG5 aUDXOgBEA02JPaFLQCHpjqxuZAGyjvQkosJgcg5ACNNRnoUFC/Fga9SOrlzxWVduOtTEZSBA4r7Mc /HpVXTbhmPdCFKOIFGSPxxwPC48OmjgvkqVwpNBpsumxcWpvdG93Borp8oTaN+i0TOgBMG0/FNIgC LZQRe83Je4zqxMmJxL4UNrI4tVdw2NIWOTkw2RsHgkL0PGWHu+VNm8forptW6CQPEuNhznIwNF4uQ g1ijujJNiwIJkz/Nba/NjyfkYvoFOrrmC4zJ8+EyBWtCzPscUliqQbvynCmtrGuPeGq5WPthzMuBk AotoV87Q==; Received: from hch by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1oWfHo-00GqRQ-01; Fri, 09 Sep 2022 14:47:16 +0000 Date: Fri, 9 Sep 2022 07:47:15 -0700 From: Christoph Hellwig To: Robin Murphy Cc: Christoph Hellwig , Will McVicker , Jingoo Han , Gustavo Pimentel , Lorenzo Pieralisi , Rob Herring , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Bjorn Helgaas , kernel-team@android.com, Vidya Sagar , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, kernel test robot Subject: Re: [PATCH v5 2/2] PCI: dwc: Add support for 64-bit MSI target address Message-ID: References: <20220825185026.3816331-1-willmcvicker@google.com> <20220825185026.3816331-3-willmcvicker@google.com> <5bfd7d4d-d431-6321-89bc-663dcd36e930@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5bfd7d4d-d431-6321-89bc-663dcd36e930@arm.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, Sep 09, 2022 at 02:47:19PM +0100, Robin Murphy wrote: > On 2022-09-09 14:29, Christoph Hellwig wrote: > > On Thu, Aug 25, 2022 at 06:50:25PM +0000, Will McVicker wrote: > > > Since not all devices require a 32-bit MSI address, add support to the > > > PCIe host driver to allow setting the DMA mask to 64-bits if the 32-bit > > > allocation fails. This allows kernels to disable ZONE_DMA32 and bounce > > > buffering (swiotlb) without risking not being able to get a 32-bit address > > > during DMA allocation. > > > > Umm. You can't just disable ZONE_DMA32. Linux absolutely requires a > > 32-bit dma mask to work, it is in fact the implicit default. > > Eh, it's behind CONFIG_EXPERT, which makes it enough of a "I think I know > what I'm doing and accept responsibility for picking up the pieces if it > breaks" thing. Seem like indeed on arm64 there is a way to disable it. The x86 model is to just select it unconditionally, which I think is the right way if we don't want to get into completely random failures.