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

[David Gibson]

On Mon, Apr 24, 2017 at 05:29:52PM +0200, Thomas Huth 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.
> 
> I wonder why this was working when the XHCI controller was connected
> directly to the PHB? Do the memory regions behave differently here?
> 
> > 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 think this patch is right. Using prefetchable memory here was
> certainly a bad idea, and if I get the PCI-to-PCI bridge spec right,
> there is no such thing like a dedicated 64-bit non-prefetchable memory
> range, so using the non-prefetchable 32-bit memory range is the only
> option here.

That is my understanding as well.

> 
> Reviewed-by: Thomas Huth <thuth at redhat.com>
> 
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-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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