This just allows read/write of three feature bits. ASID is still
ignored. Any writes to TTBR0_EL0 and TTBR1_EL0, including changing
the ASID, will still cause a complete flush of the TLB.

Signed-off-by: Jim MacArthur <jim.macarthur@linaro.org>
---
 target/arm/cpu-features.h | 7 +++++++
 target/arm/helper.c       | 3 +++
 target/arm/tcg/cpu64.c    | 4 ++++
 3 files changed, 14 insertions(+)

diff --git a/target/arm/cpu-features.h b/target/arm/cpu-features.h
index 579fa8f8f4..d56bda9ce0 100644
--- a/target/arm/cpu-features.h
+++ b/target/arm/cpu-features.h
@@ -346,6 +346,8 @@ FIELD(ID_AA64MMFR3, SDERR, 52, 4)
 FIELD(ID_AA64MMFR3, ADERR, 56, 4)
 FIELD(ID_AA64MMFR3, SPEC_FPACC, 60, 4)
 
+FIELD(ID_AA64MMFR4, ASID2, 8, 4)
+
 FIELD(ID_AA64DFR0, DEBUGVER, 0, 4)
 FIELD(ID_AA64DFR0, TRACEVER, 4, 4)
 FIELD(ID_AA64DFR0, PMUVER, 8, 4)
@@ -1369,6 +1371,11 @@ static inline bool isar_feature_aa64_aie(const ARMISARegisters *id)
     return FIELD_EX64_IDREG(id, ID_AA64MMFR3, AIE) != 0;
 }
 
+static inline bool isar_feature_aa64_asid2(const ARMISARegisters *id)
+{
+    return FIELD_EX64_IDREG(id, ID_AA64MMFR4, ASID2) != 0;
+}
+
 static inline bool isar_feature_aa64_mec(const ARMISARegisters *id)
 {
     return FIELD_EX64_IDREG(id, ID_AA64MMFR3, MEC) != 0;
diff --git a/target/arm/helper.c b/target/arm/helper.c
index c20334fa65..b380ade957 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6102,6 +6102,9 @@ static void tcr2_el1_write(CPUARMState *env, const ARMCPRegInfo *ri,
     if (cpu_isar_feature(aa64_aie, cpu)) {
         valid_mask |= TCR2_AIE;
     }
+    if (cpu_isar_feature(aa64_asid2, cpu)) {
+        valid_mask |= TCR2_FNG1 | TCR2_FNG0 | TCR2_A2;
+    }
     value &= valid_mask;
     raw_write(env, ri, value);
 }
diff --git a/target/arm/tcg/cpu64.c b/target/arm/tcg/cpu64.c
index 6871956382..ef4c0c8d73 100644
--- a/target/arm/tcg/cpu64.c
+++ b/target/arm/tcg/cpu64.c
@@ -1334,6 +1334,10 @@ void aarch64_max_tcg_initfn(Object *obj)
     t = FIELD_DP64(t, ID_AA64MMFR3, AIE, 1);      /* FEAT_AIE */
     SET_IDREG(isar, ID_AA64MMFR3, t);
 
+    t = GET_IDREG(isar, ID_AA64MMFR4);
+    t = FIELD_DP64(t, ID_AA64MMFR4, ASID2, 1);    /* FEAT_ASID2 */
+    SET_IDREG(isar, ID_AA64MMFR4, t);
+
     t = GET_IDREG(isar, ID_AA64ZFR0);
     t = FIELD_DP64(t, ID_AA64ZFR0, SVEVER, 2);    /* FEAT_SVE2p1 */
     t = FIELD_DP64(t, ID_AA64ZFR0, AES, 2);       /* FEAT_SVE_PMULL128 */
-- 
2.43.0

On 11/12/25 10:17, Jim MacArthur wrote:
> @@ -6102,6 +6102,9 @@ static void tcr2_el1_write(CPUARMState *env, const ARMCPRegInfo *ri,
>       if (cpu_isar_feature(aa64_aie, cpu)) {
>           valid_mask |= TCR2_AIE;
>       }
> +    if (cpu_isar_feature(aa64_asid2, cpu)) {
> +        valid_mask |= TCR2_FNG1 | TCR2_FNG0 | TCR2_A2;
> +    }
>       value &= valid_mask;
>       raw_write(env, ri, value);
>   }

These same bits also need to be enabled in tcr2_el2_write.

Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~