linux-kernel - Re: [PATCH 23/23] x86, PCI: add pcibios_root

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Message-ID: <CAE9FiQV23maKVMrk7h1cJxYfxrqJcKu7GfwFYUJfSDfh8g-KFQ@mail.gmail.com>
Date:	Tue, 6 Mar 2012 22:29:46 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bjorn.helgaas@...il.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>, x86 <x86@...nel.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 23/23] x86, PCI: add pcibios_root_rescan

On Tue, Mar 6, 2012 at 7:49 PM, Bjorn Helgaas <bjorn.helgaas@...il.com> wrote:

>> my sandbridge system has cpu bus 0x7f, and 0xff in DSDT.
>>
>> but nehalem and westmere system does not have cpu bus 0xf8, ... 0xff.
>
> I think you're saying that on some machines, the BIOS decided not to
> expose host bridges leading to CPU devices, and you want to discover
> those devices anyway.  (What's the reason you want to discover them?)

current code for mmconf will set pcibios_last_bios according to mmconf
bus range.

so it legacy peer root bus fix up will discover those cpu buses.

then if some one remove them through
echo 1 > /sys/devices/pci0000:ff/pci_bus/0000:ff/remove

then

echo 1 > /sys/bus/pci/rescan_root

will not recover those cpu buses without this patch.

Yinghai
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