Hi Ilya!
On 15/10/2025 16.21, Ilya Leoshkevich wrote:
After reset, CKC value is set to 0, so if clock-comparator interrupts
are enabled, one should occur very shortly thereafter.
Currently the code does not set tod_timer, so this does not happen.
Fix by adding a tcg_s390_tod_updated() call. Initialize TOD clock
before CPUs in order to ensure that the respective object exists
during the CPU reset.
Can this really happen? Looking at CPUS390XState in target/s390x/cpu.h, the
ckc is next to the cregs[] in the start_initial_reset_fields section, so if
ckc gets cleared, the cregs get cleared, too. I.e. if ckc gets set to 0
here, there is no way that the clock comparator interrupt could trigger
immediately without the guest writing to the control registers first. So I
think this patch is not really necessary. Or do I miss something?
Thomas
Signed-off-by: Ilya Leoshkevich <[email protected]>
---
hw/s390x/s390-virtio-ccw.c | 6 +++---
target/s390x/cpu.c | 8 ++++++++
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index ad2c48188a8..9f37a96ae5a 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -286,6 +286,9 @@ static void ccw_init(MachineState *machine)
/* init memory + setup max page size. Required for the CPU model */
s390_memory_init(machine);
+ /* init the TOD clock */
+ s390_init_tod();
+
/* init CPUs (incl. CPU model) early so s390_has_feature() works */
s390_init_cpus(machine);
@@ -332,9 +335,6 @@ static void ccw_init(MachineState *machine)
s390_create_sclpconsole(ms->sclp, "sclplmconsole", serial_hd(1));
}
- /* init the TOD clock */
- s390_init_tod();
-
/* init SCLP event Control-Program Identification */
if (s390mc->use_cpi) {
s390_create_sclpcpi(ms->sclp);
diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
index f05ce317da1..cc2de6ce08e 100644
--- a/target/s390x/cpu.c
+++ b/target/s390x/cpu.c
@@ -40,6 +40,7 @@
#include "system/reset.h"
#endif
#include "hw/s390x/cpu-topology.h"
+#include "tcg/tcg_s390x.h"
#define CR0_RESET 0xE0UL
#define CR14_RESET 0xC2000000UL;
@@ -215,6 +216,13 @@ static void s390_cpu_reset_hold(Object *obj, ResetType
type)
break;
}
}
+
+#ifndef CONFIG_USER_ONLY
+ if (tcg_enabled()) {
+ /* Rearm the CKC timer if necessary */
+ tcg_s390_tod_updated(CPU(cpu), RUN_ON_CPU_NULL);
+ }
+#endif
}
static void s390_cpu_disas_set_info(CPUState *cpu, disassemble_info *info)
