KVM does not have the means to support enabling the rva22u64 profile.
The main reasons are:

- we're missing support for some mandatory rva22u64 extensions in the
  KVM module;

- we can't make promises about enabling a profile since it all depends
  on host support in the end.

We'll revisit this decision in the future if needed. For now mark the
'rva22u64' profile as unavailable when running a KVM CPU:

$ qemu-system-riscv64 -machine virt,accel=kvm -cpu rv64,rva22u64=true
qemu-system-riscv64: can't apply global rv64-riscv-cpu.rva22u64=true:
    'rva22u64' is not available with KVM

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/kvm/kvm-cpu.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
index c6615cb807..258e360422 100644
--- a/target/riscv/kvm/kvm-cpu.c
+++ b/target/riscv/kvm/kvm-cpu.c
@@ -358,7 +358,7 @@ static void cpu_set_cfg_unavailable(Object *obj, Visitor *v,
     }
 
     if (value) {
-        error_setg(errp, "extension %s is not available with KVM",
+        error_setg(errp, "'%s' is not available with KVM",
                    propname);
     }
 }
@@ -438,6 +438,9 @@ static void kvm_riscv_add_cpu_user_properties(Object *cpu_obj)
     riscv_cpu_add_kvm_unavail_prop_array(cpu_obj, riscv_cpu_extensions);
     riscv_cpu_add_kvm_unavail_prop_array(cpu_obj, riscv_cpu_vendor_exts);
     riscv_cpu_add_kvm_unavail_prop_array(cpu_obj, riscv_cpu_experimental_exts);
+
+   /* We don't have the needed KVM support for this profile */
+   riscv_cpu_add_kvm_unavail_prop(cpu_obj, RVA22U64.name);
 }
 
 static int kvm_riscv_get_regs_core(CPUState *cs)
-- 
2.41.0