[PATCH 2/3] target/arm: Avoid assertion trying to use KVM and multiple ASes

[Peter Maydell]

KVM cannot support multiple address spaces per CPU; if you try to
create more than one then cpu_address_space_init() will assert.

In the Arm CPU realize function, detect the configurations which
would cause us to need more than one AS, and cleanly fail the
realize rather than blundering on into the assertion. This
turns this:
  $ qemu-system-aarch64  -enable-kvm -display none -cpu max -machine raspi3b
  qemu-system-aarch64: ../../softmmu/physmem.c:747: cpu_address_space_init: 
Assertion `asidx == 0 || !kvm_enabled()' failed.
  Aborted

into:
  $ qemu-system-aarch64  -enable-kvm -display none -machine raspi3b
  qemu-system-aarch64: Cannot enable KVM when guest CPU has EL3 enabled

and this:
  $ qemu-system-aarch64  -enable-kvm -display none -machine mps3-an524
  qemu-system-aarch64: ../../softmmu/physmem.c:747: cpu_address_space_init: 
Assertion `asidx == 0 || !kvm_enabled()' failed.
  Aborted

into:
  $ qemu-system-aarch64  -enable-kvm -display none -machine mps3-an524
  qemu-system-aarch64: Cannot enable KVM when using an M-profile guest CPU

Fixes: https://gitlab.com/qemu-project/qemu/-/issues/528
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 2866dd76588..4377f3211c8 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -1419,6 +1419,29 @@ static void arm_cpu_realizefn(DeviceState *dev, Error 
**errp)
         }
     }
 
+    if (kvm_enabled()) {
+        /*
+         * Catch all the cases which might cause us to create more than one
+         * address space for the CPU (otherwise we will assert() later in
+         * cpu_address_space_init()).
+         */
+        if (arm_feature(env, ARM_FEATURE_M)) {
+            error_setg(errp,
+                       "Cannot enable KVM when using an M-profile guest CPU");
+            return;
+        }
+        if (cpu->has_el3) {
+            error_setg(errp,
+                       "Cannot enable KVM when guest CPU has EL3 enabled");
+            return;
+        }
+        if (cpu->tag_memory) {
+            error_setg(errp,
+                       "Cannot enable KVM when guest CPUs has MTE enabled");
+            return;
+        }
+    }
+
     {
         uint64_t scale;
 
-- 
2.20.1