Subject: Re: [PATCH V11 07/17] powerpc/pci: Don't unset pci resources for VFs

From: Wei Yang <[email-masked]>
Date: Tue, 10 Feb 2015 14:25:44 +0800

On Tue, Feb 10, 2015 at 01:14:11PM +1100, Benjamin Herrenschmidt wrote:
>On Tue, 2015-02-10 at 09:51 +0800, Wei Yang wrote:
>> On Tue, Feb 10, 2015 at 11:36:24AM +1100, Benjamin Herrenschmidt wrote:
>> >On Thu, 2015-01-15 at 10:27 +0800, Wei Yang wrote:
>> >> If we're going to reassign resources with flag PCI_REASSIGN_ALL_RSRC, all
>> >> resources will be cleaned out during device header fixup time and then get
>> >> reassigned by PCI core. However, the VF resources won't be reassigned and
>> >> thus, we shouldn't clean them out.
>> >> 
>> >> This patch adds a condition. If the pci_dev is a VF, skip the resource
>> >> unset process.
>> >
>> >I don't understand this, can you elaborate ? Why wouldn't we reassign
>> >the IOV resource just like everything else ?
>> 
>> Sure.
>> 
>> VFs work a little bit different from normal devices. On powernv platform, we
>> have PCI_REASSIGN_ALL_RSRC set, which means all resource retrieved from
>> hardware will be cleaned and re-assigned by kernel. While VF's resources are
>> calculated from PF's IOV BAR, in virtfn_add(). And after this, there is not
>> re-assign process for VFs.
>
>I still don't undertand, you mean SR-IOV is assigned before we assign
>everybody else ? That doesn't make sense to me...
>

PF's resource will be assigned first, including normal BARs and IOV BARs.

Then PF's driver will create VFs, in virtfn_add(). In this function, VF's
resources is calculated from its PF's IOV BAR.

If you reset VF's resource as PFs, no one will try to assign it again.

>Ben.
>
>> >
>> >Ben.
>> >
>> >> Signed-off-by: Wei Yang <[email-masked]>
>> >> ---
>> >>  arch/powerpc/kernel/pci-common.c |    4 ++++
>> >>  1 file changed, 4 insertions(+)
>> >> 
>> >> diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
>> >> index 37d512d..889f743 100644
>> >> --- a/arch/powerpc/kernel/pci-common.c
>> >> +++ b/arch/powerpc/kernel/pci-common.c
>> >> @@ -788,6 +788,10 @@ static void pcibios_fixup_resources(struct pci_dev *dev)
>> >>  		       pci_name(dev));
>> >>  		return;
>> >>  	}
>> >> +
>> >> +	if (dev->is_virtfn)
>> >> +		return;
>> >> +
>> >>  	for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
>> >>  		struct resource *res = dev->resource + i;
>> >>  		struct pci_bus_region reg;
>> >
>> 
>

-- 
Richard Yang
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