target/arm: Implement FEAT_HPDS2 as a no-op

This feature allows the operating system to set TCR_ELx.HWU*
to allow the implementation to use the PBHA bits from the
block and page descriptors for for IMPLEMENTATION DEFINED
purposes.  Since QEMU has no need to use these bits, we may
simply ignore them.
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 20230811214031.171020-11-richard.henderson@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

docs/system/arm/emulation.rst

@@ -40,6 +40,7 @@ the following architecture extensions:
 - FEAT_HAFDBS (Hardware management of the access flag and dirty bit state)
 - FEAT_HCX (Support for the HCRX_EL2 register)
 - FEAT_HPDS (Hierarchical permission disables)
+- FEAT_HPDS2 (Translation table page-based hardware attributes)
 - FEAT_I8MM (AArch64 Int8 matrix multiplication instructions)
 - FEAT_IDST (ID space trap handling)
 - FEAT_IESB (Implicit error synchronization event)

target/arm/tcg/cpu32.c

@@ -62,7 +62,7 @@ void aa32_max_features(ARMCPU *cpu)
     cpu->isar.id_mmfr3 = t;
 
     t = cpu->isar.id_mmfr4;
-    t = FIELD_DP32(t, ID_MMFR4, HPDS, 1);         /* FEAT_AA32HPD */
+    t = FIELD_DP32(t, ID_MMFR4, HPDS, 2);         /* FEAT_HPDS2 */
     t = FIELD_DP32(t, ID_MMFR4, AC2, 1);          /* ACTLR2, HACTLR2 */
     t = FIELD_DP32(t, ID_MMFR4, CNP, 1);          /* FEAT_TTCNP */
     t = FIELD_DP32(t, ID_MMFR4, XNX, 1);          /* FEAT_XNX */

target/arm/tcg/cpu64.c

@@ -852,7 +852,7 @@ void aarch64_max_tcg_initfn(Object *obj)
     t = FIELD_DP64(t, ID_AA64MMFR1, HAFDBS, 2);   /* FEAT_HAFDBS */
     t = FIELD_DP64(t, ID_AA64MMFR1, VMIDBITS, 2); /* FEAT_VMID16 */
     t = FIELD_DP64(t, ID_AA64MMFR1, VH, 1);       /* FEAT_VHE */
-    t = FIELD_DP64(t, ID_AA64MMFR1, HPDS, 1);     /* FEAT_HPDS */
+    t = FIELD_DP64(t, ID_AA64MMFR1, HPDS, 2);     /* FEAT_HPDS2 */
     t = FIELD_DP64(t, ID_AA64MMFR1, LO, 1);       /* FEAT_LOR */
     t = FIELD_DP64(t, ID_AA64MMFR1, PAN, 3);      /* FEAT_PAN3 */
     t = FIELD_DP64(t, ID_AA64MMFR1, XNX, 1);      /* FEAT_XNX */