[RFC PATCH v2 2/5] Add basic MTE support to KVM guest

[Haibo Xu]

Enable the virt machine feature "mte" to work with
KVM guest. This feature is still hiden from the user
in this patch, and will be available in a later patch.

Signed-off-by: Haibo Xu <haibo.xu@linaro.org>
---
 hw/arm/virt.c      | 22 +++++++++++-----------
 target/arm/cpu.c   |  2 +-
 target/arm/kvm.c   |  9 +++++++++
 target/arm/kvm64.c |  7 +++++++
 4 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index aa2bbd14e0..76658b93a3 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1988,18 +1988,18 @@ static void machvirt_init(MachineState *machine)
         }
 
         if (vms->mte) {
+            /*
+             * The property exists only if MemTag is supported.
+             * If it is, we must allocate the ram to back that up.
+             */
+            if (!object_property_find(cpuobj, "tag-memory")) {
+                error_report("MTE requested, but not supported "
+                             "by the guest CPU");
+                exit(1);
+            }
+
             /* Create the memory region only once, but link to all cpus. */
-            if (!tag_sysmem) {
-                /*
-                 * The property exists only if MemTag is supported.
-                 * If it is, we must allocate the ram to back that up.
-                 */
-                if (!object_property_find(cpuobj, "tag-memory")) {
-                    error_report("MTE requested, but not supported "
-                                 "by the guest CPU");
-                    exit(1);
-                }
-
+            if (!tag_sysmem && !kvm_enabled()) {
                 tag_sysmem = g_new(MemoryRegion, 1);
                 memory_region_init(tag_sysmem, OBJECT(machine),
                                    "tag-memory", UINT64_MAX / 32);
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index ae04884408..47bf817b61 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -1847,7 +1847,7 @@ static void arm_cpu_realizefn(DeviceState *dev, Error 
**errp)
                                cpu->secure_memory);
     }
 
-    if (cpu->tag_memory != NULL) {
+    if (cpu->tag_memory != NULL && !kvm_enabled()) {
         cpu_address_space_init(cs, ARMASIdx_TagNS, "cpu-tag-memory",
                                cpu->tag_memory);
         if (has_secure) {
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index d8381ba224..3403e621ac 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -32,6 +32,7 @@
 #include "hw/boards.h"
 #include "hw/irq.h"
 #include "qemu/log.h"
+#include "hw/arm/virt.h"
 
 const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
@@ -274,6 +275,14 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
         }
     }
 
+    if (kvm_check_extension(s, KVM_CAP_ARM_MTE) &&
+        object_dynamic_cast(OBJECT(ms), TYPE_VIRT_MACHINE) &&
+        VIRT_MACHINE(ms)->mte) {
+            if (kvm_vm_enable_cap(s, KVM_CAP_ARM_MTE, 0)) {
+                error_report("Failed to enable KVM_CAP_ARM_MTE cap");
+            }
+    }
+
     return ret;
 }
 
diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
index dff85f6db9..73a191f8e1 100644
--- a/target/arm/kvm64.c
+++ b/target/arm/kvm64.c
@@ -500,6 +500,7 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
      */
     int fdarray[3];
     bool sve_supported;
+    bool mte_supported;
     uint64_t features = 0;
     uint64_t t;
     int err;
@@ -646,6 +647,7 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
     }
 
     sve_supported = ioctl(fdarray[0], KVM_CHECK_EXTENSION, KVM_CAP_ARM_SVE) > 
0;
+    mte_supported = ioctl(fdarray[0], KVM_CHECK_EXTENSION, KVM_CAP_ARM_MTE) > 
0;
 
     kvm_arm_destroy_scratch_host_vcpu(fdarray);
 
@@ -659,6 +661,11 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures 
*ahcf)
         t = FIELD_DP64(t, ID_AA64PFR0, SVE, 1);
         ahcf->isar.id_aa64pfr0 = t;
     }
+    if (mte_supported) {
+        t = ahcf->isar.id_aa64pfr1;
+        t = FIELD_DP64(t, ID_AA64PFR1, MTE, 2);
+        ahcf->isar.id_aa64pfr1 = t;
+    }
 
     /*
      * We can assume any KVM supporting CPU is at least a v8
-- 
2.17.1