Nina Schoetterl-Glausch <n...@linux.ibm.com> wrote:
> Hi,
>
> We're seeing failures running s390x migration kvm-unit-tests tests with TCG.
As this is tcg, could you tell the exact command that you are running?
Does it needs to be in s390x host, rigth?
$ time ./tests/qtest/migration-test
# random seed: R02S940c4f22abc48b14868566639d3d6c77
# Skipping test: s390x host with KVM is required
1..0
real 0m0.003s
user 0m0.002s
sys 0m0.001s
> Some initial findings:
> What seems to be happening is that after migration a control block
> header accessed by the test code is all zeros which causes an
> unexpected exception.
What exception?
What do you mean here by control block header?
> I did a bisection which points to c8df4a7aef ("migration: Split
> save_live_pending() into state_pending_*") as the culprit.
> The migration issue persists after applying the fix e264705012 ("migration: I
> messed state_pending_exact/estimate") on top of c8df4a7aef.
>
> Applying
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 56ff9cd29d..2dc546cf28 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3437,7 +3437,7 @@ static void ram_state_pending_exact(void *opaque,
> uint64_t max_size,
>
> uint64_t remaining_size = rs->migration_dirty_pages * TARGET_PAGE_SIZE;
>
> - if (!migration_in_postcopy()) {
> + if (!migration_in_postcopy() && remaining_size < max_size) {
If block is all zeros, then remaining_size should be zero, so always
smaller than max_size.
I don't really fully understand what is going here.
> qemu_mutex_lock_iothread();
> WITH_RCU_READ_LOCK_GUARD() {
> migration_bitmap_sync_precopy(rs);
>
> on top fixes or hides the issue. (The comparison was removed by c8df4a7aef.)
> I arrived at this by experimentation, I haven't looked into why this makes a
> difference.
>
> Any thoughts on the matter appreciated.
Later, Juan.
