target/s390x: AP-passthrough for PV guests

Enabling AP-passthrough(AP-pt) for PV-guest by using the new CPU
features for PV-AP-pt of KVM.

As usual QEMU first checks which CPU features are available and then
sets them if available and selected by user. An additional check is done
to verify that PV-AP can only be enabled if "regular" AP-pt is enabled
as well. Note that KVM itself does not enforce this restriction.

Reviewed-by: Michael Mueller <mimu@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
Message-ID: <20230823142219.1046522-6-seiden@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

1 files changed, 70 insertions, 0 deletions

diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index f034b06..bc5c56a 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -2299,6 +2299,42 @@ static bool ap_enabled(const S390FeatBitmap features)
     return test_bit(S390_FEAT_AP, features);
 }
 
+static bool uv_feat_supported(void)
+{
+    return kvm_vm_check_attr(kvm_state, KVM_S390_VM_CPU_MODEL,
+                             KVM_S390_VM_CPU_PROCESSOR_UV_FEAT_GUEST);
+}
+
+static int query_uv_feat_guest(S390FeatBitmap features)
+{
+    struct kvm_s390_vm_cpu_uv_feat prop = {};
+    struct kvm_device_attr attr = {
+        .group = KVM_S390_VM_CPU_MODEL,
+        .attr = KVM_S390_VM_CPU_MACHINE_UV_FEAT_GUEST,
+        .addr = (uint64_t) &prop,
+    };
+    int rc;
+
+    /* AP support check is currently the only user of the UV feature test */
+    if (!(uv_feat_supported() && ap_available())) {
+        return 0;
+    }
+
+    rc = kvm_vm_ioctl(kvm_state, KVM_GET_DEVICE_ATTR, &attr);
+    if (rc) {
+        return  rc;
+    }
+
+    if (prop.ap) {
+        set_bit(S390_FEAT_UV_FEAT_AP, features);
+    }
+    if (prop.ap_intr) {
+        set_bit(S390_FEAT_UV_FEAT_AP_INTR, features);
+    }
+
+    return 0;
+}
+
 static int kvm_to_feat[][2] = {
     { KVM_S390_VM_CPU_FEAT_ESOP, S390_FEAT_ESOP },
     { KVM_S390_VM_CPU_FEAT_SIEF2, S390_FEAT_SIE_F2 },
@@ -2493,11 +2529,38 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *model, Error **errp)
         set_bit(S390_FEAT_DIAG_318, model->features);
     }
 
+    /* Test for Ultravisor features that influence secure guest behavior */
+    query_uv_feat_guest(model->features);
+
     /* strip of features that are not part of the maximum model */
     bitmap_and(model->features, model->features, model->def->full_feat,
                S390_FEAT_MAX);
 }
 
+static int configure_uv_feat_guest(const S390FeatBitmap features)
+{
+    struct kvm_s390_vm_cpu_uv_feat uv_feat = {};
+    struct kvm_device_attr attribute = {
+        .group = KVM_S390_VM_CPU_MODEL,
+        .attr = KVM_S390_VM_CPU_PROCESSOR_UV_FEAT_GUEST,
+        .addr = (__u64) &uv_feat,
+    };
+
+    /* AP support check is currently the only user of the UV feature test */
+    if (!(uv_feat_supported() && ap_enabled(features))) {
+        return 0;
+    }
+
+    if (test_bit(S390_FEAT_UV_FEAT_AP, features)) {
+        uv_feat.ap = 1;
+    }
+    if (test_bit(S390_FEAT_UV_FEAT_AP_INTR, features)) {
+        uv_feat.ap_intr = 1;
+    }
+
+    return kvm_vm_ioctl(kvm_state, KVM_SET_DEVICE_ATTR, &attribute);
+}
+
 static void kvm_s390_configure_apie(bool interpret)
 {
     uint64_t attr = interpret ? KVM_S390_VM_CRYPTO_ENABLE_APIE :
@@ -2561,6 +2624,13 @@ void kvm_s390_apply_cpu_model(const S390CPUModel *model, Error **errp)
     if (ap_enabled(model->features)) {
         kvm_s390_configure_apie(true);
     }
+
+    /* configure UV-features for the guest indicated via query / test_bit */
+    rc = configure_uv_feat_guest(model->features);
+    if (rc) {
+        error_setg(errp, "KVM: Error configuring CPU UV features %d", rc);
+        return;
+    }
 }
 
 void kvm_s390_restart_interrupt(S390CPU *cpu)