target-arm: Add MDCR_EL2

Add the MDCR_EL2 register. We don't implement any of
the debug-related traps this register controls yet, so
currently it simply reads back as written.
Signed-off-by: NSergey Fedorov <serge.fdrv@gmail.com>
Message-id: 1444383794-16767-1-git-send-email-serge.fdrv@gmail.com
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
[PMM: tweaked commit message; moved non-dummy definition from
debug_cp_reginfo to el2_cp_reginfo.]
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target-arm/cpu.h

@@ -380,6 +380,7 @@ typedef struct CPUARMState {
         uint64_t dbgwcr[16]; /* watchpoint control registers */
         uint64_t mdscr_el1;
         uint64_t oslsr_el1; /* OS Lock Status */
+        uint64_t mdcr_el2;
         /* If the counter is enabled, this stores the last time the counter
          * was reset. Otherwise it stores the counter value
          */

target-arm/helper.c

@@ -3227,6 +3227,9 @@ static const ARMCPRegInfo el3_no_el2_cp_reginfo[] = {
     { .name = "CNTHP_CTL_EL2", .state = ARM_CP_STATE_BOTH,
       .opc0 = 3, .opc1 = 4, .crn = 14, .crm = 2, .opc2 = 1,
       .access = PL2_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
+    { .name = "MDCR_EL2", .state = ARM_CP_STATE_BOTH,
+      .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 1,
+      .access = PL2_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
     REGINFO_SENTINEL
 };
 
@@ -3448,6 +3451,15 @@ static const ARMCPRegInfo el2_cp_reginfo[] = {
       .resetvalue = 0,
       .writefn = gt_hyp_ctl_write, .raw_writefn = raw_write },
 #endif
+    /* The only field of MDCR_EL2 that has a defined architectural reset value
+     * is MDCR_EL2.HPMN which should reset to the value of PMCR_EL0.N; but we
+     * don't impelment any PMU event counters, so using zero as a reset
+     * value for MDCR_EL2 is okay
+     */
+    { .name = "MDCR_EL2", .state = ARM_CP_STATE_BOTH,
+      .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 1,
+      .access = PL2_RW, .resetvalue = 0,
+      .fieldoffset = offsetof(CPUARMState, cp15.mdcr_el2), },
     REGINFO_SENTINEL
 };