From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp05.in.ibm.com ([122.248.162.5]:38946 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753251Ab2FEG0L (ORCPT ); Tue, 5 Jun 2012 02:26:11 -0400 Received: from /spool/local by e28smtp05.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 5 Jun 2012 11:56:08 +0530 Date: Tue, 5 Jun 2012 14:26:03 +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: <20120605062603.GA21952@richard> Reply-To: Richard Yang References: <20120514015536.GA3331@richard> <20120514064615.GB26605@richard> <20120516011833.GA6599@richard> <20120529115900.GA31679@richard> <20120604133457.GA2969@richard> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: Sender: linux-pci-owner@vger.kernel.org List-ID: On Mon, Jun 04, 2012 at 04:36:33PM -0700, Yinghai Lu wrote: >On Mon, Jun 4, 2012 at 6:34 AM, Richard Yang wrote: >> 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? > >that should be handled by busn_alloc branch. > >kernel will try to probe in [1,15] at first, and could extend B1 range >to [1, 31] if needed. Hmm... when do you think this branch will be merged to the mainstream? > >Thanks > >Yinghai -- Richard Yang Help you, Help me