target/arm: Correctly implement Feat_DoubleLock

The architecture defines the OS DoubleLock as a register which
(similarly to the OS Lock) suppresses debug events for use in CPU
powerdown sequences.  This functionality is required in Arm v7 and
v8.0; from v8.2 it becomes optional and in v9 it must not be
implemented.

Currently in QEMU we implement the OSDLR_EL1 register as a NOP.  This
is wrong both for the "feature implemented" and the "feature not
implemented" cases: if the feature is implemented then the DLK bit
should read as written and cause suppression of debug exceptions, and
if it is not implemented then the bit must be RAZ/WI.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index c533ad0..1f4f3e0 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -500,6 +500,7 @@
         uint64_t dbgwcr[16]; /* watchpoint control registers */
         uint64_t mdscr_el1;
         uint64_t oslsr_el1; /* OS Lock Status */
+        uint64_t osdlr_el1; /* OS DoubleLock status */
         uint64_t mdcr_el2;
         uint64_t mdcr_el3;
         /* Stores the architectural value of the counter *the last time it was
@@ -2253,6 +2254,15 @@
 FIELD(DBGDIDR, BRPS, 24, 4)
 FIELD(DBGDIDR, WRPS, 28, 4)
 
+FIELD(DBGDEVID, PCSAMPLE, 0, 4)
+FIELD(DBGDEVID, WPADDRMASK, 4, 4)
+FIELD(DBGDEVID, BPADDRMASK, 8, 4)
+FIELD(DBGDEVID, VECTORCATCH, 12, 4)
+FIELD(DBGDEVID, VIRTEXTNS, 16, 4)
+FIELD(DBGDEVID, DOUBLELOCK, 20, 4)
+FIELD(DBGDEVID, AUXREGS, 24, 4)
+FIELD(DBGDEVID, CIDMASK, 28, 4)
+
 FIELD(MVFR0, SIMDREG, 0, 4)
 FIELD(MVFR0, FPSP, 4, 4)
 FIELD(MVFR0, FPDP, 8, 4)
@@ -3731,6 +3741,11 @@
     return FIELD_EX32(id->id_dfr0, ID_DFR0, COPDBG) >= 8;
 }
 
+static inline bool isar_feature_aa32_doublelock(const ARMISARegisters *id)
+{
+    return FIELD_EX32(id->dbgdevid, DBGDEVID, DOUBLELOCK) > 0;
+}
+
 /*
  * 64-bit feature tests via id registers.
  */
@@ -4155,6 +4170,11 @@
     return FIELD_EX64(id->id_aa64smfr0, ID_AA64SMFR0, FA64);
 }
 
+static inline bool isar_feature_aa64_doublelock(const ARMISARegisters *id)
+{
+    return FIELD_SEX64(id->id_aa64dfr0, ID_AA64DFR0, DOUBLELOCK) >= 0;
+}
+
 /*
  * Feature tests for "does this exist in either 32-bit or 64-bit?"
  */