Not sync the SME sysregs if SME2 is not available.
Disable SME when nested virt is on.

Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr>
---
 target/arm/hvf/hvf.c | 29 +++++++++++++++++++----------
 target/arm/hvf_arm.h |  5 +++++
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index 8d1333cbb4..cb05db2358 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -1163,6 +1163,9 @@ static bool hvf_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
 
     if (hvf_nested_virt_enabled()) {
         FIELD_DP64_IDREG(&host_isar, ID_AA64DFR0, PMUVER, 0x1);
+        /* SME is not implemented with nested virt on the Apple side */
+        SET_IDREG(&host_isar, ID_AA64PFR1,
+              GET_IDREG(&host_isar, ID_AA64PFR1) & ~R_ID_AA64PFR1_SME_MASK);
     }
 
     ahcf->isar = host_isar;
@@ -1370,16 +1373,22 @@ int hvf_arch_init_vcpu(CPUState *cpu)
             arm_cpu->cpreg_indexes[sregs_cnt++] = kvm_id;
         }
     }
-    if (__builtin_available(macOS 15.2, *)) {
-        for (i = 0; i < ARRAY_SIZE(hvf_sreg_list_sme2); i++) {
-            hv_sys_reg_t hvf_id = hvf_sreg_list_sme2[i].sreg;
-            uint64_t kvm_id = HVF_TO_KVMID(hvf_id);
-            uint32_t key = kvm_to_cpreg_id(kvm_id);
-            const ARMCPRegInfo *ri = get_arm_cp_reginfo(arm_cpu->cp_regs, key);
-
-            if (ri) {
-                assert(!(ri->type & ARM_CP_NO_RAW));
-                arm_cpu->cpreg_indexes[sregs_cnt++] = kvm_id;
+    if (hvf_arm_sme2_supported()) {
+        /*
+         * Clang doesn't allow us to combine the two checks together.
+         * -Wunsupported-availability-guard
+         */
+        if (__builtin_available(macOS 15.2, *)) {
+            for (i = 0; i < ARRAY_SIZE(hvf_sreg_list_sme2); i++) {
+                hv_sys_reg_t hvf_id = hvf_sreg_list_sme2[i].sreg;
+                uint64_t kvm_id = HVF_TO_KVMID(hvf_id);
+                uint32_t key = kvm_to_cpreg_id(kvm_id);
+                const ARMCPRegInfo *ri = get_arm_cp_reginfo(arm_cpu->cp_regs, key);
+
+                if (ri) {
+                    assert(!(ri->type & ARM_CP_NO_RAW));
+                    arm_cpu->cpreg_indexes[sregs_cnt++] = kvm_id;
+                }
             }
         }
         /*
diff --git a/target/arm/hvf_arm.h b/target/arm/hvf_arm.h
index 6b1c3b9792..9cb58ad9ab 100644
--- a/target/arm/hvf_arm.h
+++ b/target/arm/hvf_arm.h
@@ -11,6 +11,7 @@
 #ifndef QEMU_HVF_ARM_H
 #define QEMU_HVF_ARM_H
 
+#include "system/hvf.h"
 #include "target/arm/cpu-qom.h"
 
 /**
@@ -35,6 +36,10 @@ void hvf_arm_set_cpu_features_from_host(ARMCPU *cpu);
         if (__builtin_available(macOS 15.2, *)) {
             size_t svl_bytes;
             hv_return_t result = hv_sme_config_get_max_svl_bytes(&svl_bytes);
+            /* Nested virt not supported together with SME right now. */
+            if (hvf_nested_virt_enabled()) {
+                return false;
+            }
             if (result == HV_UNSUPPORTED) {
                 return false;
             }
-- 
2.50.1 (Apple Git-155)