PCI IO regions must be power of two

[Marcelo Tosatti <marcelo@kvack.org>]

Anthony,

Both virtio-net and virtio-block currently register PCI IO space regions
that are not power of two in size.

The decoding process to discover the size of a PCI resource expects it
to be a power of two. The PCI controller masks the size out of what is
written into

config_space + 0x10 + (4 * region_num)

The result is that the size is calculated and registered erroneously 
by the OS:

[root@localhost ~]# cat /proc/ioports  | grep virtio
  c200-c203 : virtio-pci

This is a virtio-block device whose BAR0 has length (16+20)-1, not 4. 

      BAR0: I/O at 0xc200 [0xc223].

I suggest forcing the size to be power of two as follows:


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))) {
+        size = size << 1;
+        size &= size-1;
+    }
+
     r = &pci_dev->io_regions[region_num];
     r->addr = -1;
     r->size = size;


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