hw/arm/virt: Disable pl011 clock migration if needed

A clock is added by commit aac63e0e6ea3 ("hw/char/pl011: add a clock
input") since v5.2.0 which corresponds to virt-5.2 machine type. It
causes backwards migration failure from upstream to downstream (v5.1.0)
when the machine type is specified with virt-5.1.

This fixes the issue by following instructions from section "Connecting
subsections to properties" in docs/devel/migration.rst. With this applied,
the PL011 clock is migrated based on the machine type.

   virt-5.2 or newer:  migration
   virt-5.1 or older:  non-migration

Cc: qemu-stable@nongnu.org # v5.2.0+
Fixes: aac63e0e6ea3 ("hw/char/pl011: add a clock input")
Suggested-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Message-id: 20210318023801.18287-1-gshan@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/hw/char/pl011.c b/hw/char/pl011.c
index c5621a195f..dc85527a5f 100644
--- a/hw/char/pl011.c
+++ b/hw/char/pl011.c
@@ -322,10 +322,18 @@ static const MemoryRegionOps pl011_ops = {
     .endianness = DEVICE_NATIVE_ENDIAN,
 };
 
+static bool pl011_clock_needed(void *opaque)
+{
+    PL011State *s = PL011(opaque);
+
+    return s->migrate_clk;
+}
+
 static const VMStateDescription vmstate_pl011_clock = {
     .name = "pl011/clock",
     .version_id = 1,
     .minimum_version_id = 1,
+    .needed = pl011_clock_needed,
     .fields = (VMStateField[]) {
         VMSTATE_CLOCK(clk, PL011State),
         VMSTATE_END_OF_LIST()
@@ -363,6 +371,7 @@ static const VMStateDescription vmstate_pl011 = {
 
 static Property pl011_properties[] = {
     DEFINE_PROP_CHR("chardev", PL011State, chr),
+    DEFINE_PROP_BOOL("migrate-clk", PL011State, migrate_clk, true),
     DEFINE_PROP_END_OF_LIST(),
 };