linux-kernel - Re: [PATCH 2/2] PCI, ACPI, x86: update MMCFG information when hot-plugging PCI host bridges

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Message-ID: <CAE9FiQWZwkyp8F7HDTpGVZ=Q=09_68NR3tT_vCzwFH3ZhXDzCA@mail.gmail.com>
Date:	Tue, 10 Apr 2012 08:47:27 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
Cc:	Jiang Liu <liuj97@...il.com>,
	Taku Izumi <izumi.taku@...fujitsu.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Keping Chen <chenkeping@...wei.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 2/2] PCI, ACPI, x86: update MMCFG information when
 hot-plugging PCI host bridges

On Tue, Apr 10, 2012 at 3:32 AM, Kenji Kaneshige
<kaneshige.kenji@...fujitsu.com> wrote:
> Additionally, I think there is a remaining issue even if we change
> this check like below.
>
>
>        if (!!(pci_probe & PCI_PROBE_MASK & ~PCI_PROBE_MMCONF))
>                return 0;
>
> I think this check has an assumption that system has at least one
> MCFG table entry and it has been initialized before
> acpi_pci_root_add() is called. I think this doesn't work on the
> system that doesn't have MCFG and all the pci root bridge have
> _CBA (that is, all host bridges are hot-pluggable and BIOS is
> implemented in the way PCI FW spec defines). As a result, MMCONFIG
> would never be enabled on such systems. Could you double check this?

You are right.

We can just remove that checking.

But wonder if current x86_64 system support that.
All peer root buses can be physically removed ?

Thanks

Yinghai
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