target/arm: Query host CPU features on-demand at instance init

Currently we query the host CPU features in the class init function
for the TYPE_ARM_HOST_CPU class, so that we can later copy them
from the class object into the instance object in the object
instance init function. This is awkward for implementing "-cpu max",
which should work like "-cpu host" for KVM but like "cpu with all
implemented features" for TCG.

Move the place where we store the information about the host CPU from
a class object to static variables in kvm.c, and then in the instance
init function call a new kvm_arm_set_cpu_features_from_host()
function which will query the host kernel if necessary and then
fill in the CPU instance fields.

This allows us to drop the special class struct and class init
function for TYPE_ARM_HOST_CPU entirely.

We can't delay the probe until realize, because the ARM
instance_post_init hook needs to look at the feature bits we
set, so we need to do it in the initfn. This is safe because
the probing doesn't affect the actual VM state (it creates a
separate scratch VM to do its testing), but the probe might fail.
Because we can't report errors in retrieving the host features
in the initfn, we check this belatedly in the realize function
(the intervening code will be able to cope with the relevant
fields in the CPU structure being zero).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20180308130626.12393-2-peter.maydell@linaro.org

1 files changed, 24 insertions, 11 deletions

diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
index cfb7e5af72..1e2364007d 100644
--- a/target/arm/kvm_arm.h
+++ b/target/arm/kvm_arm.h
@@ -152,20 +152,16 @@ bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
 void kvm_arm_destroy_scratch_host_vcpu(int *fdarray);
 
 #define TYPE_ARM_HOST_CPU "host-" TYPE_ARM_CPU
-#define ARM_HOST_CPU_CLASS(klass) \
-    OBJECT_CLASS_CHECK(ARMHostCPUClass, (klass), TYPE_ARM_HOST_CPU)
-#define ARM_HOST_CPU_GET_CLASS(obj) \
-    OBJECT_GET_CLASS(ARMHostCPUClass, (obj), TYPE_ARM_HOST_CPU)
-
-typedef struct ARMHostCPUClass {
-    /*< private >*/
-    ARMCPUClass parent_class;
-    /*< public >*/
 
+/**
+ * ARMHostCPUFeatures: information about the host CPU (identified
+ * by asking the host kernel)
+ */
+typedef struct ARMHostCPUFeatures {
     uint64_t features;
     uint32_t target;
     const char *dtb_compatible;
-} ARMHostCPUClass;
+} ARMHostCPUFeatures;
 
 /**
  * kvm_arm_get_host_cpu_features:
@@ -174,8 +170,16 @@ typedef struct ARMHostCPUClass {
  * Probe the capabilities of the host kernel's preferred CPU and fill
  * in the ARMHostCPUClass struct accordingly.
  */
-bool kvm_arm_get_host_cpu_features(ARMHostCPUClass *ahcc);
+bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf);
 
+/**
+ * kvm_arm_set_cpu_features_from_host:
+ * @cpu: ARMCPU to set the features for
+ *
+ * Set up the ARMCPU struct fields up to match the information probed
+ * from the host CPU.
+ */
+void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu);
 
 /**
  * kvm_arm_sync_mpstate_to_kvm
@@ -200,6 +204,15 @@ void kvm_arm_pmu_init(CPUState *cs);
 
 #else
 
+static inline void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)
+{
+    /* This should never actually be called in the "not KVM" case,
+     * but set up the fields to indicate an error anyway.
+     */
+    cpu->kvm_target = QEMU_KVM_ARM_TARGET_NONE;
+    cpu->host_cpu_probe_failed = true;
+}
+
 static inline int kvm_arm_vgic_probe(void)
 {
     return 0;