Re: [PATCH v2 25/26] PCI: Disable mem in the ioapic removing path

Yinghai Lu
2013-02-08T22:33:19Z

On Fri, Feb 8, 2013 at 1:14 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> On Fri, Feb 8, 2013 at 12:28 PM, Yinghai Lu <yinghai@kernel.org> wrote:
>> For physical hot plug should be ok, but for remove/rescan path will
>> need us to disable that.
>>
>> otherwise rescan mmio resource for pci ioapic device will not be
>> sized and allocated, aka skiped.
>
> When we scan other PCI devices, we can size memory BARs even if
> PCI_COMMAND_MEMORY is already set. So there must be something
> different about IOAPICs? Or maybe it's something different about
> rescan vs. the initial scan?

it is in drivers/pci/setup-bus.c::__dev_sort_resources()
it will skip the reallocation for ioapic controller.

...
/* Don't touch ioapic devices already enabled by firmware */
if (class == PCI_CLASS_SYSTEM_PIC) {
u16 command;
pci_read_config_word(dev, PCI_COMMAND, &command);
if (command & (PCI_COMMAND_IO | PCI_COMMAND_MEMORY))
return;
}

>
>> For ioapic_probe:pci_enable_device will not enable the device
>> correctly, and will bail out early.
>
> Exactly where and why do we bail out early? The only early bail out I
> see is where __pci_enable_device_flags() returns if "dev->enable_cnt >
> 1". Is that what you mean?

pci_enable_device==>pci_enable_device_flags
==>do_pci_enable_device==>pcibios_enable_device==>pci_enable_resources
...
if (!r->parent) {
dev_err(&dev->dev, "device not available "
"(can't reserve %pR)\n", r);
return -EINVAL;
}
...

only reassign one will have get it's parent.

Thanks

Yinghai