s390x/kvm: fix small race reboot vs. cmma

Right now we reset all devices before we reset the cmma states.  This
can result in the host kernel discarding guest pages that were
previously in the unused state but already contain a bios or a -kernel
file before the cmma reset has finished.  This race results in random
guest crashes or hangs during very early reboot.

Fixes: 1cd4e0f6f0a6 ("s390x/cmma: clean up cmma reset")
Cc: qemu-stable@nongnu.org
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
(cherry picked from commit 1a0e4c8b02ea510508970c333ee610a90b921cbb)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/s390x/s390-virtio.c b/hw/s390x/s390-virtio.c
index 0a963473ad486b7d5983b7f8cdf22781f6b5921a..7a3a7fe5fd518217c098daf8f736599fda17639f 100644 (file)
--- a/hw/s390x/s390-virtio.c
+++ b/hw/s390x/s390-virtio.c
@@ -204,8 +204,8 @@ void s390_machine_reset(void)
 {
     S390CPU *ipl_cpu = S390_CPU(qemu_get_cpu(0));
 
-    qemu_devices_reset();
     s390_cmma_reset();
+    qemu_devices_reset();
     s390_crypto_reset();
 
     /* all cpus are stopped - configure and start the ipl cpu only */