Re: PCI IO regions must be power of two

[Marcelo Tosatti <marcelo@kvack.org>]

On Wed, Mar 12, 2008 at 08:39:11AM -0700, Uri Lublin wrote:
> From: Marcelo Tosatti
> >
> >Index: kvm-userspace.hotplug2/qemu/hw/pci.c
> >===================================================================
> >--- kvm-userspace.hotplug2.orig/qemu/hw/pci.c
> >+++ kvm-userspace.hotplug2/qemu/hw/pci.c
> >@@ -236,6 +236,13 @@ void pci_register_io_region(PCIDevice *p
> >
> >     if ((unsigned int)region_num >= PCI_NUM_REGIONS)
> >         return;
> >+
> >+    /* IO region size must be power of two */
> >+    if (type == PCI_ADDRESS_SPACE_IO && (size & (size-1))) {
> 
> Why only for PCI IO regions ? Don't PCI memory regions have the same restriction ?

Yes, they do.

> >+        size = size << 1;
> >+        size &= size-1;
> 
> That would not make size a power of 2 (e.g. size=7 --> size=12).

Right, sorry.

I'll resend a patch to have virtio allocate IO regions with proper sizes
and warn if the IO _or_ memory region are not power of two, as Anthony
suggested.

Since this problem is only visible with device hotplug (QEMU will
allocate the region offsets properly during initialization) I'll wait
for that to hit the tree.

Thanks.

-------------------------------------------------------------------------
This SF.net email is sponsored by: Microsoft
Defy all challenges. Microsoft(R) Visual Studio 2008.
http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/