From: Richard Yang <weiyang@linux.vnet.ibm.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: Richard Yang <weiyang@linux.vnet.ibm.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: One problem in reassign pci bus number?
Date: Tue, 5 Jun 2012 14:26:03 +0800 [thread overview]
Message-ID: <20120605062603.GA21952@richard> (raw)
In-Reply-To: <CAE9FiQWw=dMBajvGQy_1KoPbGa1wvER5U81oULbkXCjBzQDRpQ@mail.gmail.com>
On Mon, Jun 04, 2012 at 04:36:33PM -0700, Yinghai Lu wrote:
>On Mon, Jun 4, 2012 at 6:34 AM, Richard Yang <weiyang@linux.vnet.ibm.com> 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
>>><weiyang@linux.vnet.ibm.com> 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
next prev parent reply other threads:[~2012-06-05 6:26 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120410090306.GA7056@richard>
2012-04-22 15:52 ` One problem in reassign pci bus number? Richard Yang
2012-04-23 19:46 ` Don Dutile
2012-04-23 20:19 ` Yinghai Lu
2012-04-23 21:09 ` Don Dutile
2012-04-23 22:07 ` Yinghai Lu
2012-04-25 2:56 ` Don Dutile
2012-04-23 22:22 ` Yinghai Lu
2012-04-25 2:59 ` Don Dutile
2012-04-24 7:29 ` Richard Yang
2012-05-14 1:55 ` Richard Yang
2012-05-14 5:40 ` Yinghai Lu
2012-05-14 6:46 ` Richard Yang
2012-05-15 17:32 ` Yinghai Lu
2012-05-16 1:18 ` Richard Yang
2012-05-16 2:11 ` Yinghai Lu
2012-05-29 11:59 ` Richard Yang
2012-05-29 17:14 ` Yinghai Lu
2012-06-04 13:34 ` Richard Yang
2012-06-04 23:36 ` Yinghai Lu
2012-06-05 6:26 ` Richard Yang [this message]
2012-06-05 18:01 ` Yinghai Lu
2012-04-23 20:13 ` Yinghai Lu
2012-04-24 14:56 ` Wei Yang
2012-04-25 9:47 ` Wei Yang
2012-04-25 16:28 ` Yinghai Lu
2012-05-03 6:54 ` Richard Yang
2012-05-03 8:33 ` Yinghai Lu
2012-05-04 2:47 ` Richard Yang
2012-05-04 3:15 ` Yinghai Lu
2012-05-04 4:52 ` Richard Yang
2012-05-04 17:37 ` Yinghai Lu
2012-05-06 15:17 ` Richard Yang
2012-05-06 16:35 ` Yinghai Lu
2012-05-06 16:36 ` Yinghai Lu
2012-05-07 1:17 ` Richard Yang
2012-05-07 2:04 ` Yinghai Lu
2012-05-08 2:46 ` Richard Yang
2012-05-08 3:42 ` Yinghai Lu
2012-05-10 3:35 ` Richard Yang
2012-05-10 5:42 ` Yinghai Lu
2012-05-11 1:23 ` Richard Yang
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