[PATCH 1/2] target/arm: Suppress more TCG unimplemented features in ID registers

[Peter Maydell]

We already squash the ID register field for FEAT_SPE (the Statistical
Profiling Extension) because TCG does not implement it and if we
advertise it to the guest the guest will crash trying to look at
non-existent system registers.  Do the same for some other features
which a real hardware Neoverse-V1 implements but which TCG doesn't:
 * FEAT_TRF (Self-hosted Trace Extension)
 * Trace Macrocell system register access
 * Memory mapped trace
 * FEAT_AMU (Activity Monitors Extension)
 * FEAT_MPAM (Memory Partitioning and Monitoring Extension)
 * FEAT_NV (Nested Virtualization)

Most of these, like FEAT_SPE, are "introspection/trace" type features
which QEMU is unlikely to ever implement.  The odd-one-out here is
FEAT_NV -- we could implement that and at some point we probably
will.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.c | 33 +++++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index a1e77698ba2..7eb7e909097 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -2048,13 +2048,38 @@ static void arm_cpu_realizefn(DeviceState *dev, Error 
**errp)
 
     if (tcg_enabled()) {
         /*
-         * Don't report the Statistical Profiling Extension in the ID
-         * registers, because TCG doesn't implement it yet (not even a
-         * minimal stub version) and guests will fall over when they
-         * try to access the non-existent system registers for it.
+         * Don't report some architectural features in the ID registers
+         * where TCG does not yet implement it (not even a minimal
+         * stub version). This avoids guests falling over when they
+         * try to access the non-existent system registers for them.
          */
+        /* FEAT_SPE (Statistical Profiling Extension) */
         cpu->isar.id_aa64dfr0 =
             FIELD_DP64(cpu->isar.id_aa64dfr0, ID_AA64DFR0, PMSVER, 0);
+        /* FEAT_TRF (Self-hosted Trace Extension) */
+        cpu->isar.id_aa64dfr0 =
+            FIELD_DP64(cpu->isar.id_aa64dfr0, ID_AA64DFR0, TRACEFILT, 0);
+        cpu->isar.id_dfr0 =
+            FIELD_DP32(cpu->isar.id_dfr0, ID_DFR0, TRACEFILT, 0);
+        /* Trace Macrocell system register access */
+        cpu->isar.id_aa64dfr0 =
+            FIELD_DP64(cpu->isar.id_aa64dfr0, ID_AA64DFR0, TRACEVER, 0);
+        cpu->isar.id_dfr0 =
+            FIELD_DP32(cpu->isar.id_dfr0, ID_DFR0, COPTRC, 0);
+        /* Memory mapped trace */
+        cpu->isar.id_dfr0 =
+            FIELD_DP32(cpu->isar.id_dfr0, ID_DFR0, MMAPTRC, 0);
+        /* FEAT_AMU (Activity Monitors Extension) */
+        cpu->isar.id_aa64pfr0 =
+            FIELD_DP64(cpu->isar.id_aa64pfr0, ID_AA64PFR0, AMU, 0);
+        cpu->isar.id_pfr0 =
+            FIELD_DP32(cpu->isar.id_pfr0, ID_PFR0, AMU, 0);
+        /* FEAT_MPAM (Memory Partitioning and Monitoring Extension) */
+        cpu->isar.id_aa64pfr0 =
+            FIELD_DP64(cpu->isar.id_aa64pfr0, ID_AA64PFR0, MPAM, 0);
+        /* FEAT_NV (Nested Virtualization) */
+        cpu->isar.id_aa64mmfr2 =
+            FIELD_DP64(cpu->isar.id_aa64mmfr2, ID_AA64MMFR2, NV, 0);
     }
 
     /* MPU can be configured out of a PMSA CPU either by setting has-mpu
-- 
2.34.1