From: "hnick@vmware.com" <hnick@vmware.com>

Signed-off-by: Nick Hudson <hnick@vmware.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index a66c1f0b9eb..910ace42741 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6326,11 +6326,21 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
       .access = PL1_RW, .accessfn = access_tda,
       .fieldoffset = offsetof(CPUARMState, cp15.mdscr_el1),
       .resetvalue = 0 },
-    /* MDCCSR_EL0, aka DBGDSCRint. This is a read-only mirror of MDSCR_EL1.
+    /*
+     * MDCCSR_EL0[30:29] map to EDSCR[30:29].  Simply RAZ as the external
+     * Debug Communication Channel is not implemented.
+     */
+    { .name = "MDCCSR_EL0", .state = ARM_CP_STATE_AA64,
+      .opc0 = 2, .opc1 = 3, .crn = 0, .crm = 1, .opc2 = 0,
+      .access = PL0_R, .accessfn = access_tda,
+      .type = ARM_CP_CONST, .resetvalue = 0 },
+    /*
+     * DBGDSCRint[15,12,5:2] map to MDSCR_EL1[15,12,5:2].  Map all bits as
+     * it is unlikely a guest will care.
      * We don't implement the configurable EL0 access.
      */
-    { .name = "MDCCSR_EL0", .state = ARM_CP_STATE_BOTH,
-      .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 1, .opc2 = 0,
+    { .name = "DBGDSCRint", .state = ARM_CP_STATE_AA32,
+      .cp = 14, .opc1 = 0, .crn = 0, .crm = 1, .opc2 = 0,
       .type = ARM_CP_ALIAS,
       .access = PL1_R, .accessfn = access_tda,
       .fieldoffset = offsetof(CPUARMState, cp15.mdscr_el1), },
-- 
2.20.1