hw/arm/virt: KVM: Enable PAuth when supported by the host

Add basic support for Pointer Authentication when running a KVM
guest and that the host supports it, loosely based on the SVE
support.

Although the feature is enabled by default when the host advertises
it, it is possible to disable it by setting the 'pauth=off' CPU
property. The 'pauth' comment is removed from cpu-features.rst,
as it is now common to both TCG and KVM.

Tested on an Apple M1 running 5.16-rc6.

Cc: Eric Auger <eric.auger@redhat.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220107150154.2490308-1-maz@kernel.org
[PMM: fixed indentation]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 5 insertions, 11 deletions

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index a211804fd3..cdbc4cdd01 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -1380,17 +1380,10 @@ void arm_cpu_finalize_features(ARMCPU *cpu, Error **errp)
             return;
         }
 
-        /*
-         * KVM does not support modifications to this feature.
-         * We have not registered the cpu properties when KVM
-         * is in use, so the user will not be able to set them.
-         */
-        if (!kvm_enabled()) {
-            arm_cpu_pauth_finalize(cpu, &local_err);
-            if (local_err != NULL) {
-                error_propagate(errp, local_err);
-                return;
-            }
+        arm_cpu_pauth_finalize(cpu, &local_err);
+        if (local_err != NULL) {
+            error_propagate(errp, local_err);
+            return;
         }
     }
 
@@ -2091,6 +2084,7 @@ static void arm_host_initfn(Object *obj)
     kvm_arm_set_cpu_features_from_host(cpu);
     if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
         aarch64_add_sve_properties(obj);
+        aarch64_add_pauth_properties(obj);
     }
 #else
     hvf_arm_set_cpu_features_from_host(cpu);