On 28.05.2013, at 12:18, Michael S. Tsirkin wrote:
> 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
Huh? Why not? Qemu-system-ppc64 -M pseries -m 1G should be in good enough shape
to boot your favorite Linux distro's installation DVD.
> this out for early feedback/flames.
> Testing reports also wellcome!
While the hack looks like a hack, I can't really think of anything better
either.
Alex
>
>
> 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);
