target-arm: Fix handling of SDCR for 32-bit code

Fix two issues with our implementation of the SDCR:
 * it is only present from ARMv8 onwards
 * it does not contain several of the trap bits present in its 64-bit
   counterpart the MDCR_EL3

Put the register description in the right place so that it does not
get enabled for ARMv7 and earlier, and give it a write function so that
we can mask out the bits which should not be allowed to have an effect
if EL3 is 32-bit.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 1455892784-11328-2-git-send-email-peter.maydell@linaro.org
Reviewed-by: NSergey Fedorov <serge.fdrv@gmail.com>
Acked-by: NAlistair Francis <alistair.francis@xilinx.com>

target-arm/cpu.h

@@ -598,6 +598,7 @@ void pmccntr_sync(CPUARMState *env);
 #define MDCR_EDAD     (1U << 20)
 #define MDCR_SPME     (1U << 17)
 #define MDCR_SDD      (1U << 16)
+#define MDCR_SPD      (3U << 14)
 #define MDCR_TDRA     (1U << 11)
 #define MDCR_TDOSA    (1U << 10)
 #define MDCR_TDA      (1U << 9)
@@ -606,6 +607,9 @@ void pmccntr_sync(CPUARMState *env);
 #define MDCR_TPM      (1U << 6)
 #define MDCR_TPMCR    (1U << 5)
 
+/* Not all of the MDCR_EL3 bits are present in the 32-bit SDCR */
+#define SDCR_VALID_MASK (MDCR_EPMAD | MDCR_EDAD | MDCR_SPME | MDCR_SPD)
+
 #define CPSR_M (0x1fU)
 #define CPSR_T (1U << 5)
 #define CPSR_F (1U << 6)

target-arm/helper.c

@@ -3037,6 +3037,12 @@ static CPAccessResult fpexc32_access(CPUARMState *env, const ARMCPRegInfo *ri,
     return CP_ACCESS_OK;
 }
 
+static void sdcr_write(CPUARMState *env, const ARMCPRegInfo *ri,
+                       uint64_t value)
+{
+    env->cp15.mdcr_el3 = value & SDCR_VALID_MASK;
+}
+
 static const ARMCPRegInfo v8_cp_reginfo[] = {
     /* Minimal set of EL0-visible registers. This will need to be expanded
      * significantly for system emulation of AArch64 CPUs.
@@ -3331,6 +3337,15 @@ static const ARMCPRegInfo v8_cp_reginfo[] = {
       .opc0 = 3, .opc1 = 4, .crn = 4, .crm = 3, .opc2 = 3,
       .access = PL2_RW,
       .fieldoffset = offsetof(CPUARMState, banked_spsr[BANK_FIQ]) },
+    { .name = "MDCR_EL3", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 6, .crn = 1, .crm = 3, .opc2 = 1,
+      .resetvalue = 0,
+      .access = PL3_RW, .fieldoffset = offsetof(CPUARMState, cp15.mdcr_el3) },
+    { .name = "SDCR", .type = ARM_CP_ALIAS,
+      .cp = 15, .opc1 = 0, .crn = 1, .crm = 3, .opc2 = 1,
+      .access = PL1_RW, .accessfn = access_trap_aa32s_el1,
+      .writefn = sdcr_write,
+      .fieldoffset = offsetoflow32(CPUARMState, cp15.mdcr_el3) },
     REGINFO_SENTINEL
 };
 
@@ -3688,14 +3703,6 @@ static const ARMCPRegInfo el3_cp_reginfo[] = {
       .access = PL1_RW, .accessfn = access_trap_aa32s_el1,
       .fieldoffset = offsetoflow32(CPUARMState, cp15.scr_el3),
       .writefn = scr_write },
-    { .name = "MDCR_EL3", .state = ARM_CP_STATE_AA64,
-      .opc0 = 3, .opc1 = 6, .crn = 1, .crm = 3, .opc2 = 1,
-      .resetvalue = 0,
-      .access = PL3_RW, .fieldoffset = offsetof(CPUARMState, cp15.mdcr_el3) },
-    { .name = "SDCR", .type = ARM_CP_ALIAS,
-      .cp = 15, .opc1 = 0, .crn = 1, .crm = 3, .opc2 = 1,
-      .access = PL1_RW, .accessfn = access_trap_aa32s_el1,
-      .fieldoffset = offsetoflow32(CPUARMState, cp15.mdcr_el3) },
     { .name = "SDER32_EL3", .state = ARM_CP_STATE_AA64,
       .opc0 = 3, .opc1 = 6, .crn = 1, .crm = 1, .opc2 = 1,
       .access = PL3_RW, .resetvalue = 0,