When a BE guest reads capacity from an LE host virtio-blk device or vice
versa, it will get the dwords of the qword field swapped.
As virtio-blk is the only one with such a quirk,
and as non-pci transports don't do byte-swaps at all,
solve this with a bit of device-specific hackery in
virtio-pci.
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
Changes from v1:
fixed some obvious bugs.
I don't seem to be able to boot any big-endian
guests ATM, so this is only compile-tested - sending
this out for early feedback/flames.
Testing reports also wellcome!
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 9668b2b..e7971cc 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -98,6 +98,12 @@
/* HACK for virtio to determine if it's running a big endian guest */
bool virtio_is_big_endian(void);
+#ifdef HOST_WORDS_BIGENDIAN
+#define VIRTIO_HOST_IS_BIG_ENDIAN true
+#else
+#define VIRTIO_HOST_IS_BIG_ENDIAN false
+#endif
+
static void virtio_pci_bus_new(VirtioBusState *bus, VirtIOPCIProxy *dev);
/* virtio device */
@@ -411,6 +417,15 @@ static uint64_t virtio_pci_config_read(void *opaque,
hwaddr addr,
}
break;
case 4:
+ /* Most devices don't have 64 bit config fields.
+ * Block is an exception: first 8 bytes include
+ * a 64 bit capacity field.
+ */
+ if (virtio_is_big_endian() != VIRTIO_HOST_IS_BIG_ENDIAN &&
+ proxy->vdev->device_id == VIRTIO_ID_BLOCK && addr < 8) {
+ /* Swap first two words */
+ addr ^= 0x4;
+ }
val = virtio_config_readl(proxy->vdev, addr);
if (virtio_is_big_endian()) {
val = bswap32(val);
