[PATCH v2] target/arm: Use correct variable for setting 'max' cpu's MIDR_EL1

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

MIDR_EL1 a 64-bit system register with the top 32-bit being RES0.

This fixes when compiling with -Werror=conversion:

  target/arm/cpu64.c: In function ‘aarch64_max_initfn’:
  target/arm/cpu64.c:628:21: error: conversion from ‘uint64_t’ {aka ‘long unsigned int’} to ‘uint32_t’ {aka ‘unsigned int’} may change value [-Werror=conversion]
    628 |         cpu->midr = t;
        |                     ^

Suggested-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
I suppose cp15.c0_cpuid register in target/arm/cpu.h as uint32_t is OK.

Since v1: Follow Laurent and Peter suggestion.
---
 target/arm/cpu.h | 3 ++-
 target/arm/cpu.c | 4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 8b9f2961ba..4d1be56df9 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -894,7 +894,7 @@ struct ARMCPU {
         uint64_t id_aa64dfr0;
         uint64_t id_aa64dfr1;
     } isar;
-    uint32_t midr;
+    uint64_t midr;
     uint32_t revidr;
     uint32_t reset_fpsid;
     uint32_t ctr;
@@ -1685,6 +1685,7 @@ FIELD(MIDR_EL1, PARTNUM, 4, 12)
 FIELD(MIDR_EL1, ARCHITECTURE, 16, 4)
 FIELD(MIDR_EL1, VARIANT, 20, 4)
 FIELD(MIDR_EL1, IMPLEMENTER, 24, 8)
+FIELD(MIDR_EL1, RESERVED, 32, 32)
 
 FIELD(ID_ISAR0, SWAP, 0, 4)
 FIELD(ID_ISAR0, BITCOUNT, 4, 4)
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index a79f233b17..aaa48e06ac 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -1182,6 +1182,8 @@ void arm_cpu_post_init(Object *obj)
 {
     ARMCPU *cpu = ARM_CPU(obj);
 
+    assert(FIELD_EX64(cpu->midr, MIDR_EL1, RESERVED) == 0);
+
     /* M profile implies PMSA. We have to do this here rather than
      * in realize with the other feature-implication checks because
      * we look at the PMSA bit to see if we should add some properties.
@@ -2757,7 +2759,7 @@ static const ARMCPUInfo arm_cpus[] = {
 static Property arm_cpu_properties[] = {
     DEFINE_PROP_BOOL("start-powered-off", ARMCPU, start_powered_off, false),
     DEFINE_PROP_UINT32("psci-conduit", ARMCPU, psci_conduit, 0),
-    DEFINE_PROP_UINT32("midr", ARMCPU, midr, 0),
+    DEFINE_PROP_UINT64("midr", ARMCPU, midr, 0),
     DEFINE_PROP_UINT64("mp-affinity", ARMCPU,
                         mp_affinity, ARM64_AFFINITY_INVALID),
     DEFINE_PROP_INT32("node-id", ARMCPU, node_id, CPU_UNSET_NUMA_NODE_ID),
-- 
2.21.1