[SLOF] [PATCH slof] pci: Put non-prefetchable 64bit BARs into 32bit MMIO window

[Thomas Huth]

On 27.04.2017 08:54, Alexey Kardashevskiy wrote:
> On Wed, 26 Apr 2017 15:23:40 +0200
> Thomas Huth <thuth at redhat.com> wrote:
> 
>> On 24.04.2017 05:01, Alexey Kardashevskiy wrote:
>>> At the moment 64bit non-prefetchable BARs of devices behind PCI p2p
>>> bridge go to a 64bit prefetchable windows which is not correct and
>>> causes linux guests to fail to ioremap() such resources.
>>>
>>> This moves 64bit non-prefetchable BARs 32bit non-prefetchable
>>> window.
>>>
>>> Note that this does not make distinction between P2P and PHB so
>>> from now on XHCI BARs will be allocated from 32bit MMIO space.
>>> However since most 64bit-MMIO-capable devices have prefetchable
>>> BARs, and XHCI BAR is just 4K (so it is unlikely to cause any space
>>> problems), this should not affect usual behavior.
>>>
>>> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>>> ---
>>>
>>> This fixes QEMU's XHCI when it is put on a P2P PCI bridge.
>>>
>>> There is a little naming confusion as it may look like the patch
>>> is changing assignment for all 64bit BAR but it does not as:
>>> - "mmio" is used for non-prefetchable memory,
>>> - "mem" is used for prefetchable memory.
>>> ---
>>>  slof/fs/pci-properties.fs | 6 +-----
>>>  1 file changed, 1 insertion(+), 5 deletions(-)
>>>
>>> diff --git a/slof/fs/pci-properties.fs b/slof/fs/pci-properties.fs
>>> index e6fd843..8594e5d 100644
>>> --- a/slof/fs/pci-properties.fs
>>> +++ b/slof/fs/pci-properties.fs
>>> @@ -166,11 +166,7 @@
>>>  \ Setup a non-prefetchable 64bit BAR and return its size
>>>  : assign-mmio64-bar ( bar-addr -- 8 )
>>>          dup pci-bar-size-mem64          \ fetch size
>>> -        pci-next-mem64 @ 0 = IF          \ Check if we have 64-bit
>>> memory range
>>> -	    pci-next-mmio
>>> -	ELSE
>>> -	    pci-next-mem64              \ for board-qemu we will
>>> use same range
>>> -	THEN
>>> +        pci-next-mmio
>>>          assign-bar-value64              \ and set it all
>>>  ;  
>>
>> I'm sorry, but this is now causing trouble with the USB keyboard in
>> *SLOF* instead. If I start QEMU now like this:
>>
>> qemu-system-ppc64 -nodefaults -serial mon:stdio \
>>   -device pci-bridge,bus=pci.0,id=bridge1,chassis_nr=1 \
>>   -device nec-usb-xhci,id=xhci1,bus=bridge1,addr=0x3 -vga std \
>>   -device usb-kbd,bus=xhci1.0 -bios boot_rom.bin
>>
>> then SLOF complains: "usb-xhci: failed to initialize XHCI controller"
>> and the keyboard is not working at the SLOF prompt anymore.
>>
>> Any idea why this is happening now?
> 
> 
> XHCI's usb_hcd_dev::base == 0xc0000000 which is a bus address while it
> is supposed to be a mapped address, i.e. 800000020000000.
> 
> It used to work before the patch as pci address is the same as mapped
> address - 210000000000 - and I am not sure if this is not an accident,
> could be QEMU's PCI MMIO windows/spacing rework David did some time ago.
> 
> I am trying to figure out now where usb_hcd_dev::base is set in SLOF,
> it is tricky :-/

I think the value comes from usb-setup-hcidev in pci-class_0c.fs ... so
it's likely that translate-my-address is failing now.

... but thinking about this issue again, I now wonder whether your
original patch was really the right solution here, since QEMU only
provides three memory regions to the guest:
1) I/O
2) 32-bit memory
3) 64-bit memory
There is no distinction between prefetchable and non-prefetchable here.
So I think the original problem might have been caused by something else
instead... (not sure about that yet, though)

 Thomas