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 18E60C433FE for ; Fri, 11 Nov 2022 21:06:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232372AbiKKVGB (ORCPT ); Fri, 11 Nov 2022 16:06:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230303AbiKKVGA (ORCPT ); Fri, 11 Nov 2022 16:06:00 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CA8E833AC for ; Fri, 11 Nov 2022 13:06:00 -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 ams.source.kernel.org (Postfix) with ESMTPS id B5D00B82775 for ; Fri, 11 Nov 2022 21:05:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 18EE0C433C1; Fri, 11 Nov 2022 21:05:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668200757; bh=Md7r15xpIcXrzmOMtgS/bLTu59Ct3vctpSOgUabspNg=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=mUpYujhvYF5+otrQiqVe2cmjKhLy3N8DPb8cKULRyt00bVuGwCxQ0gKzCss8CCPSX UMAk8tTCgF6H6dZUYuCo3TM0Lkj7BkwAurdyxOmsBW9Olg4HQv5IBBjxzqDkSiz4ik B3kA7fzQVDRPHpxZJeGl8oS0QYeDn7zx5DsUzUtDDkTRTN+eypBILXZuQiRCbL2SwS c5f8cC7Edr81uWxXv/qHFWMdl52+yfzWaySLpkmv2q/KiYBBs2SIJi73bKu63JJbVM dDijAIzc2yl6ulAwneFPy6CrE9K7/I2qIAoaAfw3CfEnOxOjw1shirhHyc1f5Hte1+ Qay84Fneaz8fw== Date: Fri, 11 Nov 2022 15:05:55 -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: <20221111210555.GA744899@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20221111200945.qlholxaoa2ecrfm4@pali> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org 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. Bjorn