arm/kvm: add support for MTE

Extend the 'mte' property for the virt machine to cover KVM as
well. For KVM, we don't allocate tag memory, but instead enable
the capability.

If MTE has been enabled, we need to disable migration, as we do not
yet have a way to migrate the tags as well. Therefore, MTE will stay
off with KVM unless requested explicitly.

[gankulkarni: This patch is rework of commit b320e21c48
which broke TCG since it made the TCG -cpu max
report the presence of MTE to the guest even if the board hadn't
enabled MTE by wiring up the tag RAM. This meant that if the guest
then tried to use MTE QEMU would segfault accessing the
non-existent tag RAM.]

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>
Signed-off-by: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
Message-id: 20241008114302.4855-1-gankulkarni@os.amperecomputing.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
index cfaa0d9bc7..4d293618a7 100644
--- a/target/arm/kvm_arm.h
+++ b/target/arm/kvm_arm.h
@@ -189,6 +189,13 @@ bool kvm_arm_pmu_supported(void);
 bool kvm_arm_sve_supported(void);
 
 /**
+ * kvm_arm_mte_supported:
+ *
+ * Returns: true if KVM can enable MTE, and false otherwise.
+ */
+bool kvm_arm_mte_supported(void);
+
+/**
  * kvm_arm_get_max_vm_ipa_size:
  * @ms: Machine state handle
  * @fixed_ipa: True when the IPA limit is fixed at 40. This is the case
@@ -214,6 +221,8 @@ void kvm_arm_pvtime_init(ARMCPU *cpu, uint64_t ipa);
 
 int kvm_arm_set_irq(int cpu, int irqtype, int irq, int level);
 
+void kvm_arm_enable_mte(Object *cpuobj, Error **errp);
+
 #else
 
 /*
@@ -235,6 +244,11 @@ static inline bool kvm_arm_sve_supported(void)
     return false;
 }
 
+static inline bool kvm_arm_mte_supported(void)
+{
+    return false;
+}
+
 /*
  * These functions should never actually be called without KVM support.
  */
@@ -283,6 +297,11 @@ static inline uint32_t kvm_arm_sve_get_vls(ARMCPU *cpu)
     g_assert_not_reached();
 }
 
+static inline void kvm_arm_enable_mte(Object *cpuobj, Error **errp)
+{
+    g_assert_not_reached();
+}
+
 #endif
 
 #endif