qemu-kvm: require 4K aligned resource size for memory

["Michael S. Tsirkin" <mst@redhat.com>]

KVM does not virtualize low address bits for memory accesses, so we must
require that PCI BAR size is a multiple of 4K for passthrough to work
(this also guarantees that address is 4K aligned).

Users of recent linux kernels can force resource size up to 4K
using:

	commit 32a9a682bef2f6fce7026bd94d1ce20028b0e52d
	Author: Yuji Shimada <shimada-yxb@necst.nec.co.jp>
	Date:   Mon Mar 16 17:13:39 2009 +0900
	PCI: allow assignment of memory resources with a specified alignment

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

---

diff --git a/hw/device-assignment.c b/hw/device-assignment.c
index 237060f..c2ef31f 100644
--- a/hw/device-assignment.c
+++ b/hw/device-assignment.c
@@ -381,6 +381,14 @@ static int assigned_dev_register_regions(PCIRegion *io_regions,
             int t = cur_region->type & IORESOURCE_PREFETCH
                 ? PCI_ADDRESS_SPACE_MEM_PREFETCH
                 : PCI_ADDRESS_SPACE_MEM;
+            if (cur_region->size & 0xFFF) {
+                fprintf(stderr, "Unable to assign device: PCI region %d "
+                        "at address 0x%llx has size 0x%x, "
+                        " which is not a multiple of 4K\n",
+                        i, (unsigned long long)cur_region->base_addr,
+                        cur_region->size);
+                return -1;
+            }
 
             /* map physical memory */
             pci_dev->v_addrs[i].e_physbase = cur_region->base_addr;