Re: [PATCH] hw/char/pl011: Fix clock migration failure

[Peter Maydell]

On Wed, 17 Mar 2021 at 04:44, Gavin Shan <gshan@redhat.com> wrote:
>
> There is a added clock to trace buad rate change since v5.2.0 by
> commit aac63e0e6ea3 ("hw/char/pl011: add a clock input"). The added
> clock causes migration failure. For example, migration from v5.2.0
> to v5.1.0 can fail with the following error messages:
>
>    qemu-system-aarch64: error while loading state for instance 0x0 \
>                         of device 'pl011'
>    qemu-system-aarch64: load of migration failed: No such file or \
>                         directory
>
> This fixes the issue by reporting the baud rate change at post load
> time so that the clock won't be migrated by sub-section to avoid the
> migration failure.
>
> Cc: qemu-stable@nongnu.org
> Fixes: aac63e0e6ea3 ("hw/char/pl011: add a clock input")
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  hw/char/pl011.c | 22 +++++++++-------------
>  1 file changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/hw/char/pl011.c b/hw/char/pl011.c
> index c5621a195f..401bd28536 100644
> --- a/hw/char/pl011.c
> +++ b/hw/char/pl011.c
> @@ -322,20 +322,20 @@ static const MemoryRegionOps pl011_ops = {
>      .endianness = DEVICE_NATIVE_ENDIAN,
>  };
>
> -static const VMStateDescription vmstate_pl011_clock = {
> -    .name = "pl011/clock",
> -    .version_id = 1,
> -    .minimum_version_id = 1,
> -    .fields = (VMStateField[]) {
> -        VMSTATE_CLOCK(clk, PL011State),
> -        VMSTATE_END_OF_LIST()
> -    }
> -};
> +static int pl011_post_load(void *opaque, int version_id)
> +{
> +    PL011State *s = PL011(opaque);
> +
> +    pl011_trace_baudrate_change(s);
> +
> +    return 0;
> +}
>
>  static const VMStateDescription vmstate_pl011 = {
>      .name = "pl011",
>      .version_id = 2,
>      .minimum_version_id = 2,
> +    .post_load = pl011_post_load,
>      .fields = (VMStateField[]) {
>          VMSTATE_UINT32(readbuff, PL011State),
>          VMSTATE_UINT32(flags, PL011State),
> @@ -355,10 +355,6 @@ static const VMStateDescription vmstate_pl011 = {
>          VMSTATE_INT32(read_trigger, PL011State),
>          VMSTATE_END_OF_LIST()
>      },
> -    .subsections = (const VMStateDescription * []) {
> -        &vmstate_pl011_clock,
> -        NULL
> -    }
>  };

Doesn't dropping the subsection break migration compat ?

thanks
-- PMM