[PATCH v6 0/4] Basic ASID2 support

[PATCH v6 0/4] Basic ASID2 support

[Jim MacArthur]

Enable the ID_AA64MMFR4_EL1 register, add the ASID2 field for cpu_max,
then enable writes to FNG1, FNG0, and A2 bits of TCR2_EL1. Any change
of ASID still causes a TLB flush.

Changes since V5:

- Patch 2:
  - More specific TLB flush. Now only flushes the TLBs relevant to the
    written register, and then only if A2 changes.

Thanks to Richard Henderson for advice on TLB flushing.

Signed-off-by: Jim MacArthur <jim.macarthur@linaro.org>
---
Jim MacArthur (4):
      target/arm: Enable ID_AA64MMFR4_EL1 register
      target/arm: Allow writes to FNG1, FNG0, A2
      target/arm/tcg/cpu64.c: Enable ASID2 for cpu_max
      tests: Add test for ASID2 and write/read of feature bits

 docs/system/arm/emulation.rst    |  1 +
 target/arm/cpu-features.h        |  7 ++++
 target/arm/cpu-sysregs.h.inc     |  1 +
 target/arm/helper.c              | 32 ++++++++++++-----
 target/arm/internals.h           |  5 +++
 target/arm/tcg/cpu64.c           |  4 +++
 tests/tcg/aarch64/system/asid2.c | 76 ++++++++++++++++++++++++++++++++++++++++
 7 files changed, 118 insertions(+), 8 deletions(-)
---
base-commit: 9c23f2a7b0b45277693a14074b1aaa827eecdb92
change-id: 20251210-jmac-asid2-a82ba351478d

Best regards,
-- 
Jim MacArthur <jim.macarthur@linaro.org>

[PATCH v6 1/4] target/arm: Enable ID_AA64MMFR4_EL1 register

[Jim MacArthur]

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>
Signed-off-by: Jim MacArthur <jim.macarthur@linaro.org>
---
 target/arm/cpu-sysregs.h.inc | 1 +
 target/arm/helper.c          | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/target/arm/cpu-sysregs.h.inc b/target/arm/cpu-sysregs.h.inc
index 2bb2861c62..2ba49d8478 100644
--- a/target/arm/cpu-sysregs.h.inc
+++ b/target/arm/cpu-sysregs.h.inc
@@ -14,6 +14,7 @@ DEF(ID_AA64MMFR0_EL1, 3, 0, 0, 7, 0)
 DEF(ID_AA64MMFR1_EL1, 3, 0, 0, 7, 1)
 DEF(ID_AA64MMFR2_EL1, 3, 0, 0, 7, 2)
 DEF(ID_AA64MMFR3_EL1, 3, 0, 0, 7, 3)
+DEF(ID_AA64MMFR4_EL1, 3, 0, 0, 7, 4)
 DEF(ID_PFR0_EL1, 3, 0, 0, 1, 0)
 DEF(ID_PFR1_EL1, 3, 0, 0, 1, 1)
 DEF(ID_DFR0_EL1, 3, 0, 0, 1, 2)
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 27ebc6f29b..c20334fa65 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6566,11 +6566,11 @@ void register_cp_regs_for_features(ARMCPU *cpu)
               .access = PL1_R, .type = ARM_CP_CONST,
               .accessfn = access_aa64_tid3,
               .resetvalue = GET_IDREG(isar, ID_AA64MMFR3) },
-            { .name = "ID_AA64MMFR4_EL1_RESERVED", .state = ARM_CP_STATE_AA64,
+            { .name = "ID_AA64MMFR4_EL1", .state = ARM_CP_STATE_AA64,
               .opc0 = 3, .opc1 = 0, .crn = 0, .crm = 7, .opc2 = 4,
               .access = PL1_R, .type = ARM_CP_CONST,
               .accessfn = access_aa64_tid3,
-              .resetvalue = 0 },
+              .resetvalue = GET_IDREG(isar, ID_AA64MMFR4) },
             { .name = "ID_AA64MMFR5_EL1_RESERVED", .state = ARM_CP_STATE_AA64,
               .opc0 = 3, .opc1 = 0, .crn = 0, .crm = 7, .opc2 = 5,
               .access = PL1_R, .type = ARM_CP_CONST,

-- 
2.43.0

[PATCH v6 2/4] target/arm: Allow writes to FNG1, FNG0, A2

[Jim MacArthur]

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       | 28 ++++++++++++++++++++++------
 target/arm/internals.h    |  5 +++++
 3 files changed, 34 insertions(+), 6 deletions(-)

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..534c783be9 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -428,6 +428,15 @@ int alle1_tlbmask(CPUARMState *env)
             ARMMMUIdxBit_Stage2_S);
 }
 
+int alle2_tlbmask(void)
+{
+    return (ARMMMUIdxBit_E20_2 |
+            ARMMMUIdxBit_E20_2_PAN |
+            ARMMMUIdxBit_E20_2_GCS |
+            ARMMMUIdxBit_E20_0 |
+            ARMMMUIdxBit_E20_0_GCS);
+}
+
 static const ARMCPRegInfo cp_reginfo[] = {
     /*
      * Define the secure and non-secure FCSE identifier CP registers
@@ -2802,12 +2811,7 @@ static void vmsa_tcr_ttbr_el2_write(CPUARMState *env, const ARMCPRegInfo *ri,
      */
     if (extract64(raw_read(env, ri) ^ value, 48, 16) &&
         (arm_hcr_el2_eff(env) & HCR_E2H)) {
-        uint16_t mask = ARMMMUIdxBit_E20_2 |
-                        ARMMMUIdxBit_E20_2_PAN |
-                        ARMMMUIdxBit_E20_2_GCS |
-                        ARMMMUIdxBit_E20_0 |
-                        ARMMMUIdxBit_E20_0_GCS;
-        tlb_flush_by_mmuidx(env_cpu(env), mask);
+        tlb_flush_by_mmuidx(env_cpu(env), alle2_tlbmask());
     }
     raw_write(env, ri, value);
 }
@@ -6102,6 +6106,12 @@ 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;
+        if (((raw_read(env, ri) ^ value) & TCR2_A2) != 0) {
+            tlb_flush_by_mmuidx(CPU(cpu), alle1_tlbmask(env));
+        }
+    }
     value &= valid_mask;
     raw_write(env, ri, value);
 }
@@ -6121,6 +6131,12 @@ static void tcr2_el2_write(CPUARMState *env, const ARMCPRegInfo *ri,
     if (cpu_isar_feature(aa64_mec, cpu)) {
         valid_mask |= TCR2_AMEC0 | TCR2_AMEC1;
     }
+    if (cpu_isar_feature(aa64_asid2, cpu)) {
+        valid_mask |= TCR2_FNG1 | TCR2_FNG0 | TCR2_A2;
+        if (((raw_read(env, ri) ^ value) & TCR2_A2) != 0) {
+            tlb_flush_by_mmuidx(CPU(cpu), alle2_tlbmask());
+        }
+    }
     value &= valid_mask;
     raw_write(env, ri, value);
 }
diff --git a/target/arm/internals.h b/target/arm/internals.h
index 75677945af..db9cc1fd73 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -1891,6 +1891,11 @@ uint64_t gt_direct_access_timer_offset(CPUARMState *env, int timeridx);
  * all EL1" scope; this covers stage 1 and stage 2.
  */
 int alle1_tlbmask(CPUARMState *env);
+/*
+ * Return mask of ARMMMUIdxBit values corresponding to an "invalidate
+ * all EL2&0" scope.
+ */
+int alle2_tlbmask(void);
 
 /* Set the float_status behaviour to match the Arm defaults */
 void arm_set_default_fp_behaviours(float_status *s);

-- 
2.43.0

[PATCH v6 3/4] target/arm/tcg/cpu64.c: Enable ASID2 for cpu_max

[Jim MacArthur]

docs/system/arm/emulation.rst: Add ASID2

Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>
Signed-off-by: Jim MacArthur <jim.macarthur@linaro.org>
---
 docs/system/arm/emulation.rst | 1 +
 target/arm/tcg/cpu64.c        | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/docs/system/arm/emulation.rst b/docs/system/arm/emulation.rst
index 31a5878a8f..3f30ea5a30 100644
--- a/docs/system/arm/emulation.rst
+++ b/docs/system/arm/emulation.rst
@@ -24,6 +24,7 @@ the following architecture extensions:
 - FEAT_AIE (Memory Attribute Index Enhancement)
 - FEAT_Armv9_Crypto (Armv9 Cryptographic Extension)
 - FEAT_ASID16 (16 bit ASID)
+- FEAT_ASID2 (Concurrent use of two ASIDs)
 - FEAT_ATS1A (Address Translation operations that ignore stage 1 permissions)
 - FEAT_BBM at level 2 (Translation table break-before-make levels)
 - FEAT_BF16 (AArch64 BFloat16 instructions)
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

[PATCH v6 4/4] tests: Add test for ASID2 and write/read of feature bits

[Jim MacArthur]

Test for presence of ASID2; if it is, check FNG1, FNG0, and A2 are
writable, and read value shows the update. If not present, check these
read as RES0.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Jim MacArthur <jim.macarthur@linaro.org>
---
 tests/tcg/aarch64/system/asid2.c | 76 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/tests/tcg/aarch64/system/asid2.c b/tests/tcg/aarch64/system/asid2.c
new file mode 100644
index 0000000000..7d5466af34
--- /dev/null
+++ b/tests/tcg/aarch64/system/asid2.c
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *
+ * ASID2 Feature presence and enabled TCR2_EL1 bits test
+ *
+ * Copyright (c) 2025 Linaro Ltd
+ *
+ */
+
+#include <stdint.h>
+#include <minilib.h>
+
+#define ID_AA64MMFR3_EL1 "S3_0_C0_C7_3"
+#define ID_AA64MMFR4_EL1 "S3_0_C0_C7_4"
+#define TCR2_EL1 "S3_0_C2_C0_3"
+
+int main()
+{
+    /*
+     * Test for presence of ASID2 and three feature bits enabled by it:
+     * https://developer.arm.com/documentation/109697/2025_09/Feature-descriptions/The-Armv9-5-architecture-extension
+     * Bits added are FNG1, FNG0, and A2. These should be RES0 if A2 is
+     * not enabled and read as the written value if A2 is enabled.
+     */
+
+    uint64_t out;
+    uint64_t idreg3;
+    uint64_t idreg4;
+    int tcr2_present;
+    int asid2_present;
+
+    /* Mask is FNG1, FNG0, and A2 */
+    const uint64_t feature_mask = (1ULL << 18 | 1ULL << 17 | 1ULL << 16);
+    const uint64_t in = feature_mask;
+
+    asm("mrs %[idreg3], " ID_AA64MMFR3_EL1 "\n\t"
+        : [idreg3] "=r" (idreg3));
+
+    tcr2_present = ((idreg3 & 0xF) != 0);
+
+    if (!tcr2_present) {
+        ml_printf("TCR2 is not present, cannot perform test");
+        return 0;
+    }
+
+    asm("mrs %[idreg4], " ID_AA64MMFR4_EL1 "\n\t"
+        : [idreg4] "=r" (idreg4));
+
+    asid2_present = ((idreg4 & 0xF00) != 0);
+
+    asm("msr " TCR2_EL1 ", %[x0]\n\t"
+        "mrs %[x1], " TCR2_EL1 "\n\t"
+        : [x1] "=r" (out)
+        : [x0] "r" (in));
+
+    if (asid2_present) {
+        if ((out & feature_mask) == in) {
+            ml_printf("OK\n");
+            return 0;
+        } else {
+            ml_printf("FAIL: ASID2 present, but read value %lx != "
+                      "written value %lx\n",
+                      out & feature_mask, in);
+            return 1;
+        }
+    } else {
+        if (out == 0) {
+            ml_printf("TCR2_EL1 reads as RES0 as expected\n");
+            return 0;
+        } else {
+            ml_printf("FAIL: ASID2, missing but read value %lx != 0\n",
+                      out & feature_mask, in);
+            return 1;
+        }
+    }
+}

-- 
2.43.0

Re: [PATCH v6 2/4] target/arm: Allow writes to FNG1, FNG0, A2

[Richard Henderson]

On 12/10/25 08:50, Jim MacArthur wrote:
> 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       | 28 ++++++++++++++++++++++------
>   target/arm/internals.h    |  5 +++++
>   3 files changed, 34 insertions(+), 6 deletions(-)

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

r~

Re: [PATCH v6 3/4] target/arm/tcg/cpu64.c: Enable ASID2 for cpu_max

[Richard Henderson]

On 12/10/25 08:50, Jim MacArthur wrote:
> docs/system/arm/emulation.rst: Add ASID2
> 
> Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>
> Signed-off-by: Jim MacArthur <jim.macarthur@linaro.org>
> ---
>   docs/system/arm/emulation.rst | 1 +
>   target/arm/tcg/cpu64.c        | 4 ++++
>   2 files changed, 5 insertions(+)
> 

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

r~

> diff --git a/docs/system/arm/emulation.rst b/docs/system/arm/emulation.rst
> index 31a5878a8f..3f30ea5a30 100644
> --- a/docs/system/arm/emulation.rst
> +++ b/docs/system/arm/emulation.rst
> @@ -24,6 +24,7 @@ the following architecture extensions:
>   - FEAT_AIE (Memory Attribute Index Enhancement)
>   - FEAT_Armv9_Crypto (Armv9 Cryptographic Extension)
>   - FEAT_ASID16 (16 bit ASID)
> +- FEAT_ASID2 (Concurrent use of two ASIDs)
>   - FEAT_ATS1A (Address Translation operations that ignore stage 1 permissions)
>   - FEAT_BBM at level 2 (Translation table break-before-make levels)
>   - FEAT_BF16 (AArch64 BFloat16 instructions)
> 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 */
>