Re: [PATCH 3/3] hw/arm/virt: Implement kvm-steal-time

[Andrew Jones]

On Wed, Jul 29, 2020 at 04:40:54PM +0200, Andrew Jones wrote:
> > > +static inline void kvm_arm_steal_time_finalize(ARMCPU *cpu, Error 
> > > **errp) {}
> > 
> > Does this stub need to report an error to the caller via errp,
> > or is it a "never called but needs to exist to avoid linker errors" ?
> 
> The second one, as we can't have kvm_enabled() and !defined(CONFIG_KVM).
> Hmm, these types of stubs would be more robust to refactoring if we put
> build bugs in them. I can try to analyze all the stubs in this #else to
> see which ones should be returning false/error/nothing vs. build bugging.
> 

I couldn't come up with a way to die at compile-time, but I think we
should be able to use g_assert_not_reached() in these functions. How
about something like the diff below?

Thanks,
drew


diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
index adb38514bf20..0da00eb6b20c 100644
--- a/target/arm/kvm_arm.h
+++ b/target/arm/kvm_arm.h
@@ -344,16 +344,10 @@ int kvm_arm_set_irq(int cpu, int irqtype, int irq, int 
level);
 
 #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;
-}
-
+/*
+ * It's safe to call these functions without KVM support.
+ * They should either do nothing or return "not supported".
+ */
 static inline void kvm_arm_add_vcpu_properties(Object *obj) {}
 
 static inline bool kvm_arm_aarch32_supported(void)
@@ -371,23 +365,39 @@ static inline bool kvm_arm_sve_supported(void)
     return false;
 }
 
+/*
+ * These functions should never actually be called without KVM support.
+ */
+static inline void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)
+{
+    g_assert_not_reached();
+}
+
 static inline int kvm_arm_get_max_vm_ipa_size(MachineState *ms)
 {
-    return -ENOENT;
+    g_assert_not_reached();
 }
 
 static inline int kvm_arm_vgic_probe(void)
 {
-    return 0;
+    g_assert_not_reached();
 }
 
-static inline void kvm_arm_pmu_set_irq(CPUState *cs, int irq) {}
-static inline void kvm_arm_pmu_init(CPUState *cs) {}
+static inline void kvm_arm_pmu_set_irq(CPUState *cs, int irq)
+{
+    g_assert_not_reached();
+}
 
-static inline void kvm_arm_sve_get_vls(CPUState *cs, unsigned long *map) {}
+static inline void kvm_arm_pmu_init(CPUState *cs)
+{
+    g_assert_not_reached();
+}
+
+static inline void kvm_arm_sve_get_vls(CPUState *cs, unsigned long *map)
+{
+    g_assert_not_reached();
+}
 
-static inline void kvm_arm_get_virtual_time(CPUState *cs) {}
-static inline void kvm_arm_put_virtual_time(CPUState *cs) {}
 #endif
 
 static inline const char *gic_class_name(void)