target/arm/machine: Use VMSTATE_VARRAY_INT32_ALLOC for cpreg arrays

This removes the need for explicitly allocating cpreg_vmstate arrays.
On post save we simply point to cpreg arrays and set the length
accordingly.

Remove VMSTATE_VARRAY_INT32 for cpreg_vmstate_array_len as now
the array is dynamically allocated.

Also add a trace point on post_load to trace potential mismatch
between the number of incoming cpregs versus current ones.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20260304101625.1962633-3-eric.auger@redhat.com
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/helper.c

@@ -265,15 +265,10 @@ void arm_init_cpreg_list(ARMCPU *cpu)
     if (arraylen) {
         cpu->cpreg_indexes = g_new(uint64_t, arraylen);
         cpu->cpreg_values = g_new(uint64_t, arraylen);
-        cpu->cpreg_vmstate_indexes = g_new(uint64_t, arraylen);
-        cpu->cpreg_vmstate_values = g_new(uint64_t, arraylen);
     } else {
         cpu->cpreg_indexes = NULL;
         cpu->cpreg_values = NULL;
-        cpu->cpreg_vmstate_indexes = NULL;
-        cpu->cpreg_vmstate_values = NULL;
     }
-    cpu->cpreg_vmstate_array_len = arraylen;
     cpu->cpreg_array_len = 0;
 
     g_hash_table_foreach(cpu->cp_regs, add_cpreg_to_list, cpu);

target/arm/kvm.c

@@ -864,12 +864,7 @@ static int kvm_arm_init_cpreg_list(ARMCPU *cpu)
 
     cpu->cpreg_indexes = g_renew(uint64_t, cpu->cpreg_indexes, arraylen);
     cpu->cpreg_values = g_renew(uint64_t, cpu->cpreg_values, arraylen);
-    cpu->cpreg_vmstate_indexes = g_renew(uint64_t, cpu->cpreg_vmstate_indexes,
-                                         arraylen);
-    cpu->cpreg_vmstate_values = g_renew(uint64_t, cpu->cpreg_vmstate_values,
-                                        arraylen);
     cpu->cpreg_array_len = arraylen;
-    cpu->cpreg_vmstate_array_len = arraylen;
 
     for (i = 0, arraylen = 0; i < rlp->n; i++) {
         uint64_t regidx = rlp->reg[i];

target/arm/machine.c

@@ -1,5 +1,6 @@
 #include "qemu/osdep.h"
 #include "cpu.h"
+#include "trace.h"
 #include "qemu/error-report.h"
 #include "system/kvm.h"
 #include "system/tcg.h"
@@ -984,11 +985,14 @@ static int cpu_pre_save(void *opaque)
         }
     }
 
+    /*
+     * On outbound migration, send the data in our cpreg_{values,indexes}
+     * arrays. The migration code will not allocate anything, but just
+     * reads the data pointed to by the VMSTATE_VARRAY_INT32_ALLOC() fields.
+     */
+    cpu->cpreg_vmstate_indexes = cpu->cpreg_indexes;
+    cpu->cpreg_vmstate_values = cpu->cpreg_values;
     cpu->cpreg_vmstate_array_len = cpu->cpreg_array_len;
-    memcpy(cpu->cpreg_vmstate_indexes, cpu->cpreg_indexes,
-           cpu->cpreg_array_len * sizeof(uint64_t));
-    memcpy(cpu->cpreg_vmstate_values, cpu->cpreg_values,
-           cpu->cpreg_array_len * sizeof(uint64_t));
 
     return 0;
 }
@@ -1001,6 +1005,9 @@ static int cpu_post_save(void *opaque)
         pmu_op_finish(&cpu->env);
     }
 
+    cpu->cpreg_vmstate_indexes = NULL;
+    cpu->cpreg_vmstate_values = NULL;
+
     return 0;
 }
 
@@ -1034,6 +1041,9 @@ static int cpu_pre_load(void *opaque)
         pmu_op_start(env);
     }
 
+    g_assert(!cpu->cpreg_vmstate_indexes);
+    g_assert(!cpu->cpreg_vmstate_values);
+
     return 0;
 }
 
@@ -1043,6 +1053,9 @@ static int cpu_post_load(void *opaque, int version_id)
     CPUARMState *env = &cpu->env;
     int i, v;
 
+    trace_cpu_post_load(cpu->cpreg_vmstate_array_len,
+                        cpu->cpreg_array_len);
+
     /*
      * Handle migration compatibility from old QEMU which didn't
      * send the irq-line-state subsection. A QEMU without it did not
@@ -1094,6 +1107,11 @@ static int cpu_post_load(void *opaque, int version_id)
         }
     }
 
+    g_free(cpu->cpreg_vmstate_indexes);
+    g_free(cpu->cpreg_vmstate_values);
+    cpu->cpreg_vmstate_indexes = NULL;
+    cpu->cpreg_vmstate_values = NULL;
+
     /*
      * Misaligned thumb pc is architecturally impossible. Fail the
      * incoming migration. For TCG it would trigger the assert in
@@ -1167,14 +1185,15 @@ const VMStateDescription vmstate_arm_cpu = {
         VMSTATE_UINT32_ARRAY(env.fiq_regs, ARMCPU, 5),
         VMSTATE_UINT64_ARRAY(env.elr_el, ARMCPU, 4),
         VMSTATE_UINT64_ARRAY(env.sp_el, ARMCPU, 4),
-        /* The length-check must come before the arrays to avoid
+        /*
-         * incoming data possibly overflowing the array.
+         * The length must come before the arrays so we can
+         * allocate the arrays before their data arrives
          */
-        VMSTATE_INT32_POSITIVE_LE(cpreg_vmstate_array_len, ARMCPU),
+        VMSTATE_INT32(cpreg_vmstate_array_len, ARMCPU),
-        VMSTATE_VARRAY_INT32(cpreg_vmstate_indexes, ARMCPU,
+        VMSTATE_VARRAY_INT32_ALLOC(cpreg_vmstate_indexes, ARMCPU,
                                    cpreg_vmstate_array_len,
                                    0, vmstate_info_uint64, uint64_t),
-        VMSTATE_VARRAY_INT32(cpreg_vmstate_values, ARMCPU,
+        VMSTATE_VARRAY_INT32_ALLOC(cpreg_vmstate_values, ARMCPU,
                                    cpreg_vmstate_array_len,
                                    0, vmstate_info_uint64, uint64_t),
         VMSTATE_UINT64(env.exclusive_addr, ARMCPU),

target/arm/trace-events

@@ -26,3 +26,6 @@ arm_powerctl_reset_cpu(uint64_t mp_aff) "cpu %" PRIu64
 
 # tcg/psci.c and hvf/hvf.c
 arm_psci_call(uint64_t x0, uint64_t x1, uint64_t x2, uint64_t x3, uint32_t cpuid) "PSCI Call x0=0x%016"PRIx64" x1=0x%016"PRIx64" x2=0x%016"PRIx64" x3=0x%016"PRIx64" cpuid=0x%x"
+
+# machine.c
+cpu_post_load(uint32_t cpreg_vmstate_array_len, uint32_t cpreg_array_len) "cpreg_vmstate_array_len=%d cpreg_array_len=%d"

target/arm/whpx/whpx-all.c

@@ -783,12 +783,6 @@ int whpx_init_vcpu(CPUState *cpu)
                                      sregs_match_len);
     arm_cpu->cpreg_values = g_renew(uint64_t, arm_cpu->cpreg_values,
                                     sregs_match_len);
-    arm_cpu->cpreg_vmstate_indexes = g_renew(uint64_t,
-                                             arm_cpu->cpreg_vmstate_indexes,
-                                             sregs_match_len);
-    arm_cpu->cpreg_vmstate_values = g_renew(uint64_t,
-                                            arm_cpu->cpreg_vmstate_values,
-                                            sregs_match_len);
 
     memset(arm_cpu->cpreg_values, 0, sregs_match_len * sizeof(uint64_t));
 
@@ -807,7 +801,6 @@ int whpx_init_vcpu(CPUState *cpu)
         }
     }
     arm_cpu->cpreg_array_len = sregs_cnt;
-    arm_cpu->cpreg_vmstate_array_len = sregs_cnt;
 
     assert(write_cpustate_to_list(arm_cpu, false));