linux-kernel - Re: [PATCH v2 1/8] x86/PCI: prevent re-allocation of already existing bridge and ROM resources

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Date:	Mon, 22 Jul 2013 19:18:38 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Yinghai Lu <yinghai@...nel.org>,
	"Ronciak, John" <john.ronciak@...el.com>,
	"Penner, Miles J" <miles.j.penner@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v2 1/8] x86/PCI: prevent re-allocation of already existing
 bridge and ROM resources

On Mon, Jul 22, 2013 at 6:08 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Wed, Jul 3, 2013 at 8:04 AM, Mika Westerberg
> <mika.westerberg@...ux.intel.com> wrote:
>> In hotplug case (especially with Thunderbolt enabled systems) we might need
>> to call pcibios_resource_survey_bus() several times for a bus. The function
>> ends up calling pci_claim_resource() for each bridge resource that then
>> fails claiming that the resource exists already (which it does). Once this
>> happens the resource is invalidated thus preventing devices behind the
>> bridge to allocate their resources.
>>
>> To fix this we do what has been done in pcibios_allocate_dev_resources()
>> and check 'parent' of the given resource. If it is non-NULL it means that
>> the resource has been allocated already and we can skip it. We do the same
>> for ROM resources as well.
>>
>> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
>
> This looks reasonable to me.

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> However, the use of "r->parent" to determine whether the resource is
> already allocated is nothing specific to x86.  So I think we might be
> missing an opportunity to make this more consistent across
> architectures.  I looked at other callers of pci_claim_resource() for
> bridge and ROM resources, and it looks like we might be able to make
> similar changes in:
>
>   frv pcibios_allocate_bus_resources()
>   ia64 pcibios_fixup_resources() (via pcibios_fixup_bridge_resources())
>   mn10300 pcibios_allocate_bus_resources()
>   mn10300 pcibios_assign_resources() (ROM)
>   mn10300 pcibios_fixup_device_resources()
>   parisc lba_fixup_bus()
>
> I really hate the idea of fixing something for x86 but not for other
> arches, so maybe somebody could take a deeper look at this and see if
> it would make sense to change the other arches, too.
>
> Bjorn
>
>> ---
>>  arch/x86/pci/i386.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
>> index 94919e3..db6b1ab 100644
>> --- a/arch/x86/pci/i386.c
>> +++ b/arch/x86/pci/i386.c
>> @@ -210,6 +210,8 @@ static void pcibios_allocate_bridge_resources(struct pci_dev *dev)
>>                 r = &dev->resource[idx];
>>                 if (!r->flags)
>>                         continue;
>> +               if (r->parent)  /* Already allocated */
>> +                       continue;
>>                 if (!r->start || pci_claim_resource(dev, idx) < 0) {
>>                         /*
>>                          * Something is wrong with the region.
>> @@ -318,6 +320,8 @@ static void pcibios_allocate_dev_rom_resource(struct pci_dev *dev)
>>         r = &dev->resource[PCI_ROM_RESOURCE];
>>         if (!r->flags || !r->start)
>>                 return;
>> +       if (r->parent) /* Already allocated */
>> +               return;
>>
>>         if (pci_claim_resource(dev, PCI_ROM_RESOURCE) < 0) {
>>                 r->end -= r->start;
>> --
>> 1.8.3.2
>>
--
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