migration: Enlarge postcopy recovery to capture !-EIO too

We used to have quite a few places making sure -EIO happened and that's the
only way to trigger postcopy recovery.  That's based on the assumption that
we'll only return -EIO for channel issues.

It'll work in 99.99% cases but logically that won't cover some corner cases.
One example is e.g. ram_block_from_stream() could fail with an interrupted
network, then -EINVAL will be returned instead of -EIO.

I remembered Dave Gilbert pointed that out before, but somehow this is
overlooked.  Neither did I encounter anything outside the -EIO error.

However we'd better touch that up before it triggers a rare VM data loss during
live migrating.

To cover as much those cases as possible, remove the -EIO restriction on
triggering the postcopy recovery, because even if it's not a channel failure,
we can't do anything better than halting QEMU anyway - the corpse of the
process may even be used by a good hand to dig out useful memory regions, or
the admin could simply kill the process later on.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20220301083925.33483-11-peterx@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index d08d396c63..b0d12d5053 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -1039,7 +1039,7 @@ retry:
                                         msg.arg.pagefault.address);
             if (ret) {
                 /* May be network failure, try to wait for recovery */
-                if (ret == -EIO && postcopy_pause_fault_thread(mis)) {
+                if (postcopy_pause_fault_thread(mis)) {
                     /* We got reconnected somehow, try to continue */
                     goto retry;
                 } else {