target/arm: Add arm_tlb_bti_gp

Introduce an lvalue macro to wrap target_tlb_bit0.

Backports commit 149d3b31f3f0f7f9e1c3a77043450a95c7a7e93d from qemu

qemu/target/arm/cpu.h

@@ -3251,6 +3251,19 @@ static inline uint64_t *aa64_vfp_qreg(CPUARMState *env, unsigned regno)
 /* Shared between translate-sve.c and sve_helper.c.  */
 extern const uint64_t pred_esz_masks[4];
 
+/* Helper for the macros below, validating the argument type. */
+static inline MemTxAttrs *typecheck_memtxattrs(MemTxAttrs *x)
+{
+    return x;
+}
+
+/*
+ * Lvalue macros for ARM TLB bits that we must cache in the TCG TLB.
+ * Using these should be a bit more self-documenting than using the
+ * generic target bits directly.
+ */
+#define arm_tlb_bti_gp(x) (typecheck_memtxattrs(x)->target_tlb_bit0)
+
 /*
  * Naming convention for isar_feature functions:
  * Functions which test 32-bit ID registers should have _aa32_ in

qemu/target/arm/helper.c

@@ -10850,7 +10850,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
     }
     /* When in aarch64 mode, and BTI is enabled, remember GP in the IOTLB.  */
     if (aarch64 && guarded && cpu_isar_feature(aa64_bti, cpu)) {
-        txattrs->target_tlb_bit0 = true;
+        arm_tlb_bti_gp(txattrs) = true;
     }
 
     if (cacheattrs != NULL) {

qemu/target/arm/translate-a64.c

@@ -14746,7 +14746,7 @@ static bool is_guarded_page(CPUARMState *env, DisasContext *s)
      * table entry even for that case.
      */
     return (tlb_hit(entry->addr_code, addr) &&
-            env->iotlb[mmu_idx][index].attrs.target_tlb_bit0);
+            arm_tlb_bti_gp(&env->iotlb[mmu_idx][index].attrs));
 #endif
 }