From: Eric Auger <eric.auger@redhat.com>

Currently the check of cpreg index matches fail to detect
a situation where the length of both arrays is same but
- destination has an extra register not found in the incoming stream (idx1)
- source has an extra register not found in the destination (idx2)
  where idx1 < = idx2
Normally this should fail but it does not.

Fix the logic to scan all indexes.

Fixes: 721fae12536 ("target-arm: Convert TCG to using (index,value) list for cp migration")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20260304101625.1962633-8-eric.auger@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/machine.c | 61 +++++++++++++++++++++++++++++++++++---------
 1 file changed, 49 insertions(+), 12 deletions(-)

diff --git a/target/arm/machine.c b/target/arm/machine.c
index 4d9158e697..476dad00ee 100644
--- a/target/arm/machine.c
+++ b/target/arm/machine.c
@@ -1057,6 +1057,35 @@ static gchar *print_register_name(uint64_t kvm_regidx)
     }
 }
 
+/*
+ * Handle the situation where @kvmidx is on destination but not
+ * in the incoming stream. This never fails the migration.
+ */
+static void handle_cpreg_missing_in_incoming_stream(ARMCPU *cpu, uint64_t kvmidx)
+{
+    g_autofree gchar *name = print_register_name(kvmidx);
+
+    warn_report("%s: %s "
+                "expected by the destination but not in the incoming stream: "
+                 "skip it", __func__, name);
+}
+
+/*
+ * Handle the situation where @kvmidx is in the incoming stream
+ * but not on destination. This currently fails the migration but
+ * we plan to accomodate some exceptions, hence the boolean returned value.
+ */
+static bool handle_cpreg_only_in_incoming_stream(ARMCPU *cpu, uint64_t kvmidx)
+{
+    g_autofree gchar *name = print_register_name(kvmidx);
+    bool fail = true;
+
+    error_report("%s: %s in the incoming stream but unknown on the "
+                 "destination: fail migration", __func__, name);
+
+    return fail;
+}
+
 static int cpu_post_load(void *opaque, int version_id)
 {
     ARMCPU *cpu = opaque;
@@ -1096,21 +1125,12 @@ static int cpu_post_load(void *opaque, int version_id)
     for (i = 0, v = 0; i < cpu->cpreg_array_len
              && v < cpu->cpreg_vmstate_array_len;) {
         if (cpu->cpreg_vmstate_indexes[v] > cpu->cpreg_indexes[i]) {
-            g_autofree gchar *name = print_register_name(cpu->cpreg_indexes[i]);
-
-            warn_report("%s: %s "
-                        "expected by the destination but not in the incoming stream: "
-                        "skip it", __func__, name);
-            i++;
+            handle_cpreg_missing_in_incoming_stream(cpu, cpu->cpreg_indexes[i++]);
             continue;
         }
         if (cpu->cpreg_vmstate_indexes[v] < cpu->cpreg_indexes[i]) {
-            g_autofree gchar *name = print_register_name(cpu->cpreg_vmstate_indexes[v]);
-
-            error_report("%s: %s in the incoming stream but unknown on the destination: "
-                         "fail migration", __func__, name);
-            v++;
-            fail = true;
+            fail = handle_cpreg_only_in_incoming_stream(cpu,
+                                                        cpu->cpreg_vmstate_indexes[v++]);
             continue;
         }
         /* matching register, copy the value over */
@@ -1118,6 +1138,23 @@ static int cpu_post_load(void *opaque, int version_id)
         i++;
         v++;
     }
+
+    /*
+     * if we have reached the end of the incoming array but there are
+     * still regs in cpreg, continue parsing the regs which are missing
+     * in the input stream
+     */
+    for ( ; i < cpu->cpreg_array_len; i++) {
+        handle_cpreg_missing_in_incoming_stream(cpu, cpu->cpreg_indexes[i]);
+    }
+    /*
+     * if we have reached the end of the cpreg array but there are
+     * still regs in the input stream, continue parsing the vmstate array
+     */
+    for ( ; v < cpu->cpreg_vmstate_array_len; v++) {
+        fail = handle_cpreg_only_in_incoming_stream(cpu,
+                                                    cpu->cpreg_vmstate_indexes[v]);
+    }
     if (fail) {
         return -1;
     }
-- 
2.43.0