[RFC PATCH 15/16] target/arm/kvm: Disable Realm reboot

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

A realm cannot be reset, it must be recreated from scratch. The RMM
specification defines states of a Realm as NEW -> ACTIVE -> SYSTEM_OFF,
after which the Realm can only be destroyed. A PCSI_SYSTEM_RESET call,
which normally reboots the system, puts the Realm in SYSTEM_OFF state.

QEMU does not support recreating a VM. Normally, a reboot request by the
guest causes all devices to reset, which cannot work for a Realm.
Indeed, loading images into Realm memory and changing the PC is only
allowed for a Realm in NEW state. Resetting the images for a Realm in
SYSTEM_OFF state will cause QEMU to crash with a bus error.

Handle reboot requests by the guest more gracefully, by indicating to
runstate.c that the vCPUs of a Realm are not resettable, and that QEMU
should exit.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
 target/arm/kvm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index d8655d9041..02b5e8009f 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -1071,7 +1071,8 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
 
 bool kvm_arch_cpu_check_are_resettable(void)
 {
-    return true;
+    /* A Realm cannot be reset */
+    return !kvm_arm_rme_enabled();
 }
 
 void kvm_arch_accel_class_init(ObjectClass *oc)
-- 
2.39.0