On 26/05/2024 22.33, David Hildenbrand wrote:
Am 26.05.24 um 21:44 schrieb Richard Henderson:
On 5/26/24 08:53, David Hildenbrand wrote:
Am 25.05.24 um 15:12 schrieb Nicholas Piggin:
The flic pending state is not migrated, so if the machine is migrated
while an interrupt is pending, it can be lost. This shows up in
qtest migration test, an extint is pending (due to console writes?)
and the CPU waits via s390_cpu_set_psw and expects the interrupt to
wake it. However when the flic pending state is lost, s390_cpu_has_int
returns false, so s390_cpu_exec_interrupt falls through to halting
again.
Fix this by migrating pending. This prevents the qtest from hanging.
Does service_param need to be migrated? Or the IO lists?
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
hw/intc/s390_flic.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/hw/intc/s390_flic.c b/hw/intc/s390_flic.c
index 6771645699..b70cf2295a 100644
--- a/hw/intc/s390_flic.c
+++ b/hw/intc/s390_flic.c
@@ -369,6 +369,7 @@ static const VMStateDescription
qemu_s390_flic_vmstate = {
.fields = (const VMStateField[]) {
VMSTATE_UINT8(simm, QEMUS390FLICState),
VMSTATE_UINT8(nimm, QEMUS390FLICState),
+ VMSTATE_UINT32(pending, QEMUS390FLICState),
VMSTATE_END_OF_LIST()
}
};
Likely you have to handle this using QEMU compat machines.
Well, since existing migration is broken, I don't think you have to preserve
Migration is broken only in some case "while an interrupt is pending, it can
be lost".
compatibility. But you do have to bump the version number.
Looking at it, this is TCG only, so likely we don't care that much about
migration compatibility. But I have no idea what level of compatibility we
want to support there.
Yes, this seems to only affect the TCG-only flic device, where migration has
never been working very reliably. So I think we don't really need the whole
compat-machine dance here. But I think we should at least bump the
version_id to 2 now and then use
VMSTATE_UINT32_V(pending, QEMUS390FLICState, 2);
for the new field. That way we would at least support forward migrations
without too much hassle.
Thomas
