On 09/11/16 14:45, David Gibson wrote:
> daa2369 "spapr_pci: Add a 64-bit MMIO window" subtly broke migration from
> qemu-2.7 to the current version. It split the device's MMIO window into
> two pieces for 32-bit and 64-bit MMIO.
>
> The patch included backwards compatibility code to convert the old property
> into the new format. However, the property value was also transferred in
> the migration stream and compared with a (probably unwise) VMSTATE_EQUAL.
> So, the "raw" value from 2.7 is compared to the new style converted value
> from (pre-)2.8 giving a mismatch and migration failure.
>
> Although it would be technically possible to fix this in a way allowing
> backwards migration, that would leave an ugly legacy around indefinitely.
> This patch takes the simpler approach of bumping the migration version,
> dropping the unwise VMSTATE_EQUAL (and some equally unwise ones around it)
> and ignoring them on an incoming migration.
>
> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> hw/ppc/spapr_pci.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 7cde30e..7f1cc29 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -1658,19 +1658,24 @@ static int spapr_pci_post_load(void *opaque, int
> version_id)
> return 0;
> }
>
> +static bool version_before_3(void *opaque, int version_id)
> +{
> + return version_id < 3;
> +}
> +
> static const VMStateDescription vmstate_spapr_pci = {
> .name = "spapr_pci",
> - .version_id = 2,
> + .version_id = 3,
> .minimum_version_id = 2,
> .pre_save = spapr_pci_pre_save,
> .post_load = spapr_pci_post_load,
> .fields = (VMStateField[]) {
> VMSTATE_UINT64_EQUAL(buid, sPAPRPHBState),
You could probably go one step further and get rid of @buid as well.
Nevertheless, this works,
Reviewed-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> - VMSTATE_UINT32_EQUAL(dma_liobn[0], sPAPRPHBState),
> - VMSTATE_UINT64_EQUAL(mem_win_addr, sPAPRPHBState),
> - VMSTATE_UINT64_EQUAL(mem_win_size, sPAPRPHBState),
> - VMSTATE_UINT64_EQUAL(io_win_addr, sPAPRPHBState),
> - VMSTATE_UINT64_EQUAL(io_win_size, sPAPRPHBState),
> + VMSTATE_UNUSED_TEST(version_before_3, sizeof(uint32_t) /*
> dma_liobn[0] */
> + + sizeof(uint64_t) /* mem_win_addr */
> + + sizeof(uint64_t) /* mem_win_size */
> + + sizeof(uint64_t) /* io_win_addr */
> + + sizeof(uint64_t) /* io_win_size */),
> VMSTATE_STRUCT_ARRAY(lsi_table, sPAPRPHBState, PCI_NUM_PINS, 0,
> vmstate_spapr_pci_lsi, struct spapr_pci_lsi),
> VMSTATE_INT32(msi_devs_num, sPAPRPHBState),
>
--
Alexey
