This is a 512-bit array introduced with SME2.
Save it only when ZA is in use.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/arm/cpu.h     |  3 +++
 target/arm/machine.c | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 938c990854..091a517a93 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -734,6 +734,9 @@ typedef struct CPUArchState {
     uint64_t scxtnum_el[4];
 
     struct {
+        /* SME2 ZT0 -- 512 bit array, with data ordered like ARMVectorReg. */
+        uint64_t zt0[512 / 64] QEMU_ALIGNED(16);
+
         /*
          * SME ZA storage -- 256 x 256 byte array, with bytes in host
          * word order, as we do with vfp.zregs[].  This corresponds to
diff --git a/target/arm/machine.c b/target/arm/machine.c
index d41da414b3..416fe1b7be 100644
--- a/target/arm/machine.c
+++ b/target/arm/machine.c
@@ -320,6 +320,26 @@ static const VMStateDescription vmstate_za = {
         VMSTATE_END_OF_LIST()
     }
 };
+
+static bool zt0_needed(void *opaque)
+{
+    ARMCPU *cpu = opaque;
+
+    return za_needed(cpu) && cpu_isar_feature(aa64_sme2, cpu);
+}
+
+static const VMStateDescription vmstate_zt0 = {
+    .name = "cpu/zt0",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = zt0_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64_ARRAY(env.za_state.zt0, ARMCPU,
+                             ARRAY_SIZE(((CPUARMState *)0)->za_state.zt0)),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 #endif /* AARCH64 */
 
 static bool serror_needed(void *opaque)
@@ -1104,6 +1124,7 @@ const VMStateDescription vmstate_arm_cpu = {
 #ifdef TARGET_AARCH64
         &vmstate_sve,
         &vmstate_za,
+        &vmstate_zt0,
 #endif
         &vmstate_serror,
         &vmstate_irq_line_state,
-- 
2.43.0