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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 1B11FC43381 for ; Mon, 21 Dec 2020 10:02:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DFFFB22A85 for ; Mon, 21 Dec 2020 10:02:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726242AbgLUKCX (ORCPT ); Mon, 21 Dec 2020 05:02:23 -0500 Received: from foss.arm.com ([217.140.110.172]:48292 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725854AbgLUKCX (ORCPT ); Mon, 21 Dec 2020 05:02:23 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 01EE91FB; Mon, 21 Dec 2020 02:01:37 -0800 (PST) Received: from e121166-lin.cambridge.arm.com (e121166-lin.cambridge.arm.com [10.1.196.255]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 01B2A3F718; Mon, 21 Dec 2020 02:01:35 -0800 (PST) Date: Mon, 21 Dec 2020 10:01:29 +0000 From: Lorenzo Pieralisi To: Marek Vasut Cc: linux-pci@vger.kernel.org, Bjorn Helgaas , Geert Uytterhoeven , Wolfram Sang , Yoshihiro Shimoda , linux-renesas-soc@vger.kernel.org Subject: Re: [PATCH] PCI: rcar: Always allocate MSI addresses in 32bit space Message-ID: <20201221100129.GA15846@e121166-lin.cambridge.arm.com> References: <20201016120431.7062-1-marek.vasut@gmail.com> <20201210181133.GA3766@e121166-lin.cambridge.arm.com> <83135f6f-8a98-4537-0df5-91a06af07955@gmail.com> <20201214160829.GA3623@e121166-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-renesas-soc@vger.kernel.org On Wed, Dec 16, 2020 at 06:49:54PM +0100, Marek Vasut wrote: > On 12/14/20 5:08 PM, Lorenzo Pieralisi wrote: > > On Sat, Dec 12, 2020 at 08:13:54PM +0100, Marek Vasut wrote: > > > On 12/10/20 7:11 PM, Lorenzo Pieralisi wrote: > > > > > > [...] > > > > > > > > diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c > > > > > index 1194d5f3341b..ac5c7d7573a6 100644 > > > > > --- a/drivers/pci/controller/pcie-rcar-host.c > > > > > +++ b/drivers/pci/controller/pcie-rcar-host.c > > > > > @@ -753,7 +753,7 @@ static int rcar_pcie_enable_msi(struct rcar_pcie_host *host) > > > > > } > > > > > /* setup MSI data target */ > > > > > - msi->pages = __get_free_pages(GFP_KERNEL, 0); > > > > > + msi->pages = __get_free_pages(GFP_KERNEL | GFP_DMA32, 0); > > > > > > > > This does not do what you want on !CONFIG_ZONE_DMA32 (ie arm LPAE). > > > > > > How come? I would expect GFP_DMA32 allocates a buffer below 4 GiB in any > > > case. > > > > For ARM LPAE allocation falls back to ZONE_NORMAL that happens to work > > because if there is memory > 4GB it ends up in ZONE_HIGHMEM, so this > > patch should still work on ARM LPAE too. > > > > Regardless, thoughts above the alternative approach (that saves you > > a page allocation) ? > > Since this is a bugfix, I would prefer it to be minimal. Yes, I agree with you on that. > Also, in case there was some yet undiscovered hardware bug which would > let the MSI write through, having unused memory as the MSI destination > address would only lead to write into that memory -- instead of a > write into some other address. > > Changing this to some hard-coded address (any suggestions?) can be a > subsequent patch. The idea was taking the address from the host controller inbound window (ie an address outside the dma-ranges ~(dma-ranges) and < 4GB), it should not matter which one. I agree though that this can be a subsequent patch even though usually we send for -rc* only fixes for patches that hit the previous merge window - this seems a quite longstanding (I traced it back to v3.16) one so it would wait till v5.12, there is time to refactor it. Thanks, Lorenzo