From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp02.in.ibm.com ([122.248.162.2]:48739 "EHLO e28smtp02.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754032Ab2FDNfg (ORCPT ); Mon, 4 Jun 2012 09:35:36 -0400 Received: from /spool/local by e28smtp02.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 4 Jun 2012 19:05:33 +0530 Date: Mon, 4 Jun 2012 21:34:57 +0800 From: Richard Yang To: Yinghai Lu Cc: Richard Yang , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: One problem in reassign pci bus number? Message-ID: <20120604133457.GA2969@richard> Reply-To: Richard Yang References: <20120422155202.GA13540@richard> <4F95B17B.3030401@redhat.com> <20120514015536.GA3331@richard> <20120514064615.GB26605@richard> <20120516011833.GA6599@richard> <20120529115900.GA31679@richard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-pci-owner@vger.kernel.org List-ID: On Tue, May 29, 2012 at 10:14:51AM -0700, Yinghai Lu wrote: >On Tue, May 29, 2012 at 4:59 AM, Richard Yang > wrote: >> >> I think about this issue again, this behavior of kernel will bring some >> unconvenience to the user. >> >> Do you think the kernel could handle this situation? > >in this extreme case, you may need user to do some comprise. > >We should always try to use setting from BIOS if it is sane. > >Yinghai Yinghai +-------+ | | root bridge(0,255) +---+---+ | Bus 0 -----+-----------+------------------------------+-- | | | | | | +----+----+ +-----+-----+ | | B1(1,15) | |B2(32,35) +----+----+ +-----+-----+ | Bus 1 | Bus 32 -----+----------------------- ----------- | +----+----+ | | B3 +---------+ I reread the current code, v3.4, in linus tree, git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git And I come up with another condition which will have a problem when kernel is not given the parameter, pci=assign-busses. Same condition as previous: ------------------------------------------------------------------------------- B1 and B2 works fine with the BIOS and get the bus number assigned. B3 is not probed by BIOS. Difference between the previous example: ------------------------------------------------------------------------------- In this case, B2 is assigned bus range (32, 35), which has a gap between B1 number range (1, 15). When kernel meets B3 in second pass, B3 will be assigned with bus number 16. Well, this time the bus number 16 doesn't overlap with bus number of B2. But, the pci_fixup_parent_subordinate_busnr() will not work since the pci=assign-buses is not passed to kernel. So B1's bus window is still (1,15) not (1,16). BTW, is this also a extrem case? -- Richard Yang Help you, Help me