target/arm: Implement HSTR.TTEE

In v7, the HSTR register has a TTEE bit which allows EL0/EL1 accesses
to the Thumb2EE TEECR and TEEHBR registers to be trapped to the
hypervisor. Implement these traps.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210816180305.20137-2-peter.maydell@linaro.org

target/arm/cpu.h

@@ -1541,6 +1541,8 @@ static inline void xpsr_write(CPUARMState *env, uint32_t val, uint32_t mask)
 #define SCR_ENSCXT            (1U << 25)
 #define SCR_ATA               (1U << 26)
 
+#define HSTR_TTEE (1 << 16)
+
 /* Return the current FPSCR value.  */
 uint32_t vfp_get_fpscr(CPUARMState *env);
 void vfp_set_fpscr(CPUARMState *env, uint32_t val);

target/arm/helper.c

@@ -2446,20 +2446,34 @@ static void teecr_write(CPUARMState *env, const ARMCPRegInfo *ri,
     env->teecr = value;
 }
 
+static CPAccessResult teecr_access(CPUARMState *env, const ARMCPRegInfo *ri,
+                                   bool isread)
+{
+    /*
+     * HSTR.TTEE only exists in v7A, not v8A, but v8A doesn't have T2EE
+     * at all, so we don't need to check whether we're v8A.
+     */
+    if (arm_current_el(env) < 2 && !arm_is_secure_below_el3(env) &&
+        (env->cp15.hstr_el2 & HSTR_TTEE)) {
+        return CP_ACCESS_TRAP_EL2;
+    }
+    return CP_ACCESS_OK;
+}
+
 static CPAccessResult teehbr_access(CPUARMState *env, const ARMCPRegInfo *ri,
                                     bool isread)
 {
     if (arm_current_el(env) == 0 && (env->teecr & 1)) {
         return CP_ACCESS_TRAP;
     }
-    return CP_ACCESS_OK;
+    return teecr_access(env, ri, isread);
 }
 
 static const ARMCPRegInfo t2ee_cp_reginfo[] = {
     { .name = "TEECR", .cp = 14, .crn = 0, .crm = 0, .opc1 = 6, .opc2 = 0,
       .access = PL1_RW, .fieldoffset = offsetof(CPUARMState, teecr),
       .resetvalue = 0,
-      .writefn = teecr_write },
+      .writefn = teecr_write, .accessfn = teecr_access },
     { .name = "TEEHBR", .cp = 14, .crn = 1, .crm = 0, .opc1 = 6, .opc2 = 0,
       .access = PL0_RW, .fieldoffset = offsetof(CPUARMState, teehbr),
       .accessfn = teehbr_access, .resetvalue = 0 },