Re: [PATCH v6 2/2] PCI: Try best to allocate pref mmio 64bit above 4g

[Yinghai Lu]

On Sun, Dec 22, 2013 at 5:14 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> On Sun, Dec 22, 2013 at 4:00 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote:
>> On Thu, Dec 19, 2013 at 1:44 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
>>
>> Let me see if I can figure out what you're trying to do here.  Please
>> correct me if I'm wrong:
>>
>>> When one of children resources does not support MEM_64, MEM_64 for
>>> bridge get reset, so pull down whole pref resource on the bridge under 4G.
>>
>> When we allocate space for a bridge's prefetchable window, we
>> currently look at the devices behind the bridge and put the window
>> below 4GB if any of those children has a 32-bit prefetchable BAR.
>>
>> This maximizes the use of prefetch, at the cost of using more 32-bit
>> address space.
>
> yes. and we have problem when we have 8 sockets or 32 sockets system,
> will have limit 32bit space.
> but we have enough above 4G 64bit mmio for prefetchable.
>
>>
>>> If the bridge support pref mem 64, will only allocate that with pref mem64 to
>>> children that support it.
>>> For children resources if they only support pref mem 32, will allocate them
>>> from non pref mem instead.
>>
>> You are changing this so that we will always try to put a bridge's
>> 64-bit prefetchable window above 4GB, regardless of what devices are
>> behind the bridge.  If a device behind the bridge has a 32-bit
>> prefetchable BAR, we will place that BAR in the bridge's 32-bit
>> non-prefetchable window.
>
> Yes. so we can keep IORESOURCE_MEM64 in the flags for PREF.
>
>>
>> This minimizes the use of the 32-bit address space, at the cost of not
>> being able to use prefetch as much.
>>
>>> If the bridge only support 32bit pref mmio, will still have all children pref
>>> mmio under that.
>>
>> Obviously, if a bridge has a prefetchable window that's only 32 bits,
>> 64-bit prefetchable BARs behind the bridge will have to be in that
>> 32-bit prefetchable window or the 32-bit non-prefetchable window.  And
>> if the bridge has no prefetchable window at all, every memory BAR
>> behind the bridge will have to be in the 32-bit non-prefetchable
>> window.
>
> Yes.
>
>>
>> I'll look at the actual patch later; I just want to make sure I
>> understand your intent first.

Hi, Bjorn,

Can you check and add this one to your pci/resource branch?
With that we can close the loop for 64bit mmio resource allocation.

Thanks

Yinghai
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