On 11/11/2025 09.43, Christian Borntraeger wrote:
Am 29.04.25 um 07:20 schrieb Nicholas Miehlbradt:
The reset performed by subcode 3 of the diag308 instruction specifies
that system memory should be reset. This patch implements that
behaviour.

Introduce S390_RESET_REIPL_CLEAR to differentiate between subcode 3 and
subcode 4 resets.

When doing a clear reset, discard the ramblock containing the system
ram.

Signed-off-by: Nicholas Miehlbradt <[email protected]>
---
  hw/s390x/ipl.h             | 1 +
  hw/s390x/s390-virtio-ccw.c | 6 ++++++
  target/s390x/diag.c        | 3 +--
  target/s390x/kvm/kvm.c     | 6 +++++-
  4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/hw/s390x/ipl.h b/hw/s390x/ipl.h
index cb55101f06..9c38946363 100644
--- a/hw/s390x/ipl.h
+++ b/hw/s390x/ipl.h
@@ -38,6 +38,7 @@ enum s390_reset {
      /* default is a reset not triggered by a CPU e.g. issued by QMP */
      S390_RESET_EXTERNAL = 0,
      S390_RESET_REIPL,
+    S390_RESET_REIPL_CLEAR,
      S390_RESET_MODIFIED_CLEAR,
      S390_RESET_LOAD_NORMAL,
      S390_RESET_PV,
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 94edd42dd2..bc07158b16 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -455,6 +455,7 @@ static void s390_machine_reset(MachineState *machine, ResetType type)
      enum s390_reset reset_type;
      CPUState *cs, *t;
      S390CPU *cpu;
+    RAMBlock *rb = machine->ram->ram_block;
      /*
       * Temporarily drop the record/replay mutex to let rr_cpu_thread_fn()
@@ -479,6 +480,7 @@ static void s390_machine_reset(MachineState *machine, ResetType type)
      switch (reset_type) {
      case S390_RESET_EXTERNAL:
      case S390_RESET_REIPL:
+    case S390_RESET_REIPL_CLEAR:
          /*
           * Reset the subsystem which includes a AP reset. If a PV
           * guest had APQNs attached the AP reset is a prerequisite to
@@ -489,6 +491,10 @@ static void s390_machine_reset(MachineState *machine, ResetType type)
              s390_machine_unprotect(ms);
          }
+        if (reset_type == S390_RESET_REIPL_CLEAR) {
+            ram_block_discard_range(rb, 0 , qemu_ram_get_used_length(rb));
+        }
+
          /*
           * Device reset includes CPU clear resets so this has to be
           * done AFTER the unprotect call above.
diff --git a/target/s390x/diag.c b/target/s390x/diag.c
index da44b0133e..cff9fbc4b0 100644
--- a/target/s390x/diag.c
+++ b/target/s390x/diag.c
@@ -105,8 +105,7 @@ void handle_diag_308(CPUS390XState *env, uint64_t r1, uint64_t r3, uintptr_t ra)
          s390_ipl_reset_request(cs, S390_RESET_LOAD_NORMAL);
          break;      case DIAG308_LOAD_CLEAR:
-        /* Well we still lack the clearing bit... */
-        s390_ipl_reset_request(cs, S390_RESET_REIPL);
+        s390_ipl_reset_request(cs, S390_RESET_REIPL_CLEAR);
          break;
      case DIAG308_SET:
      case DIAG308_PV_SET:
diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index b9f1422197..f2d5f7ddc0 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -1915,7 +1915,11 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
              ret = handle_intercept(cpu);
              break;
          case KVM_EXIT_S390_RESET:
-            s390_ipl_reset_request(cs, S390_RESET_REIPL);
+            if (run->s390_reset_flags & KVM_S390_RESET_CLEAR) {
+                s390_ipl_reset_request(cs, S390_RESET_REIPL_CLEAR);
+            } else {
+                s390_ipl_reset_request(cs, S390_RESET_REIPL);
+            }
              break;
          case KVM_EXIT_S390_TSCH:
              ret = handle_tsch(cpu);



Do I see that right that this patch never made it into qemu master? IIRC Matt has clarified all concerns?

I was hoping to see a reply from David that he's fine with the patch now... David?

 Thomas


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