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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Fri, 24 Jul 2015 06:48:57 +1000
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Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH v2] pci: allow 0 address for PCI
 IO/MEM regions
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Laurent Vivier <lvivier@redhat.com>, David Gibson <david@gibson.dropbear.id.au>, qemu-ppc@nongnu.org, Michael Roth <mdroth@linux.vnet.ibm.com>, qemu-devel@nongnu.org

On Thu, 2015-07-23 at 21:30 +0300, Michael S. Tsirkin wrote:
> > @@ -1075,7 +1080,8 @@ static pcibus_t pci_bar_address(PCIDevice *d,
> >          /* Check if 32 bit BAR wraps around explicitly.
> >           * TODO: make priorities correct and remove this work
> around.
> >           */
> > -        if (last_addr <= new_addr || new_addr == 0 || last_addr >=
> UINT32_MAX) {
> > +        if (last_addr <= new_addr || last_addr >= UINT32_MAX ||
> > +            (!allow_0_address && new_addr == 0)) {
> >              return PCI_BAR_UNMAPPED;
> >          }

Talking of which, how can a BAR wrap around ? BARs are always power-of
two aligned and naturally aligned (to their own size), they can't
wrap...

Ben.