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 B6340C433FE for ; Tue, 15 Nov 2022 22:15:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229637AbiKOWPG (ORCPT ); Tue, 15 Nov 2022 17:15:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55384 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229560AbiKOWPF (ORCPT ); Tue, 15 Nov 2022 17:15:05 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B77FE25F for ; Tue, 15 Nov 2022 14:15:04 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5502E61A41 for ; Tue, 15 Nov 2022 22:15:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7E645C433C1; Tue, 15 Nov 2022 22:15:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668550503; bh=99O8kLOfvn0T8dOSb/i+2MDEYfk2b9UPYRzzXoaELJQ=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=VJjP196WciP3w/Ya6rRuPgs/5Y91yd/WCvyGpdmEIUAZgjW7KOm3vdWmV1cmkP+XX pNUji1l/MDANvbVX+v1AN8MdDdMLsvs4Eb/XASPFgMjNB89YKBzU7/2fFiA/0g5dkG HmJFDwbCmBooSEBt+NjpJAVdretgXucrQcPIuFFdXjOjWCmVl/heYfsvajzzcDr3uT P5XTmVowkiuT6+ehkXGYLjLIRQYeiydVExwVJm/cmmr7PNLfyzBGyV/Isw78zyrCUo 3cGY9gs+LG7wy6siHb6C6ZTg7SIjVhIjKmEp/3irWoThsjJKkyxedD8Pqe6t20Q6aR AaiG2yr11xASA== Date: Tue, 15 Nov 2022 16:15:02 -0600 From: Bjorn Helgaas To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Martin =?utf-8?B?TWFyZcWh?= , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Matthew Wilcox , linux-pci@vger.kernel.org Subject: Re: IORESOURCE_WINDOW for PCI-to-PCI bridges Message-ID: <20221115221502.GA755872@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20221111214816.65fi63ffgvr6nbj2@pali> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, Nov 11, 2022 at 10:48:16PM +0100, Pali Rohár wrote: > On Friday 11 November 2022 15:05:55 Bjorn Helgaas wrote: > > On Fri, Nov 11, 2022 at 09:09:45PM +0100, Pali Rohár wrote: > > > On Thursday 20 January 2022 15:02:12 Bjorn Helgaas wrote: > > > > On Thu, Jan 20, 2022 at 09:45:05PM +0100, Pali Rohár wrote: > > > > [trimmed material; beginning of thread is at > > https://lore.kernel.org/r/20211220155448.1233-3-pali@kernel.org] > > > > > > > Meanwhile I found out that in linux/ioport.h file is IORESOURCE_WINDOW > > > > > constant with comment /* forwarded by bridge */ > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/ioport.h?h=v5.15#n56 > > > > > > > > > > But apparently it is not set for resources behind PCI bridges and > > > > > therefore it is not available in column of "resources" sysfs file. > > > > > > > > > > So maybe instead of adding new sysfs files, it would be better way to > > > > > implement this flag and export it in flags column of "resources" file > > > > > for every row which belongs to resources behind bridges? > > > > > > > > I looked at that, too. Today we only set IORESOURCE_WINDOW for host > > > > bridge windows. Maybe it could be set for PCI-to-PCI bridge windows, > > > > too. Would have to audit users to make sure it wouldn't break > > > > anything. > > > > > > Hello Bjorn, I would like to remind this older issue. Did you have a time > > > to audit usage of IORESOURCE_WINDOW? Some flag for resource forwarding > > > windows in PCI-to-PCI bridges would really help userspace application to > > > distinguish between IO/MEM BARs an IO/MEM forwarding windows. > > > > I had forgotten all about this issue. IIUC, the ultimate goal here > > is to help lspci distinguish between an I/O window that's disabled and > > one that's enabled at [io 0x0000-0x0fff]. > > > > I have not done the research to see whether it would be safe to set > > IORESOURCE_WINDOW for PCI-to-PCI bridge windows. I'm sorry if I left > > the impression that I intended to do that. I would welcome your help > > to do that. > > Ok, do you have some resources or other information at which I should > look? I just do not know where to start or what to check for that > research. > > I looked into kernel sources and the only places where is code checking > for IORESOURCE_WINDOW is ACPI related: arch/arm64/kernel/pci.c and > drivers/pnp/resource.c. And I do not fully understand how is ACPI > connected with PCI resources at this level. Other places which check > (lib/vsprintf.c and drivers/pnp/interface.c) just use it for > printf-formats. Yeah, that's the kind of thing I have in mind. I can't remember if I had any specific concern. Bjorn