From 90fcfe4b07afc5299c5ee69fa663ca46b597fd4b Mon Sep 17 00:00:00 2001
From: Nico Boehr <nrb@linux.ibm.com>
Date: Wed, 12 Oct 2022 14:32:29 +0200
Subject: [PATCH] s390x/tod-kvm: don't save/restore the TOD in PV guests
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RH-Author: Cédric Le Goater <clg@redhat.com>
RH-MergeRequest: 244: s390x/tod-kvm: don't save/restore the TOD in PV guests
RH-Bugzilla: 2155448
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: Thomas Huth <thuth@redhat.com>
RH-Commit: [1/1] 3cb3154dd7c1549c54cf8c0483b5f23b235f6db3
Under PV, the guest's TOD clock is under control of the ultravisor and the
hypervisor cannot change it.
With upcoming kernel changes[1], the Linux kernel will reject QEMU's
request to adjust the guest's clock in this case, so don't attempt to set
the clock.
This avoids the following warning message on save/restore of a PV guest:
warning: Unable to set KVM guest TOD clock: Operation not supported
[1] https://lore.kernel.org/all/20221011160712.928239-2-nrb@linux.ibm.com/
Fixes: c3347ed0d2ee ("s390x: protvirt: Support unpack facility")
Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Message-Id: <20221012123229.1196007-1-nrb@linux.ibm.com>
[thuth: Add curly braces]
Signed-off-by: Thomas Huth <thuth@redhat.com>
(cherry picked from commit 38621181ae3cbec62e3490fbc14f6ac01642d07a)
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
hw/s390x/tod-kvm.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/hw/s390x/tod-kvm.c b/hw/s390x/tod-kvm.c
index ec855811ae..c804c979b5 100644
--- a/hw/s390x/tod-kvm.c
+++ b/hw/s390x/tod-kvm.c
@@ -13,6 +13,7 @@
#include "qemu/module.h"
#include "sysemu/runstate.h"
#include "hw/s390x/tod.h"
+#include "hw/s390x/pv.h"
#include "kvm/kvm_s390x.h"
static void kvm_s390_get_tod_raw(S390TOD *tod, Error **errp)
@@ -84,6 +85,14 @@ static void kvm_s390_tod_vm_state_change(void *opaque, bool running,
S390TODState *td = opaque;
Error *local_err = NULL;
+ /*
+ * Under PV, the clock is under ultravisor control, hence we cannot restore
+ * it on resume.
+ */
+ if (s390_is_pv()) {
+ return;
+ }
+
if (running && td->stopped) {
/* Set the old TOD when running the VM - start the TOD clock. */
kvm_s390_set_tod_raw(&td->base, &local_err);
--
2.37.3