Enable H_CLEAR_MOD and H_CLEAR_REF hypercalls on KVM/PPC64.

These are mandatory per PAPR and available on Linux 4.3 and newer kernels. The calls in question are required to run FreeBSD guests with reasonable performance, so enable them if possible.
Signed-off-by: NNathan Whitehorn <nwhitehorn@freebsd.org>
[dwg: Added a stub to fix compile without KVM (e.g. on x86 host)]
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr.c

@@ -1814,6 +1814,9 @@ static void ppc_spapr_init(MachineState *machine)
         /* Enable H_LOGICAL_CI_* so SLOF can talk to in-kernel devices */
         kvmppc_enable_logical_ci_hcalls();
         kvmppc_enable_set_mode_hcall();
+
+        /* H_CLEAR_MOD/_REF are mandatory in PAPR, but off by default */
+        kvmppc_enable_clear_ref_mod_hcalls();
     }
 
     /* allocate RAM */

target-ppc/kvm.c

@@ -2056,6 +2056,12 @@ void kvmppc_enable_set_mode_hcall(void)
     kvmppc_enable_hcall(kvm_state, H_SET_MODE);
 }
 
+void kvmppc_enable_clear_ref_mod_hcalls(void)
+{
+    kvmppc_enable_hcall(kvm_state, H_CLEAR_REF);
+    kvmppc_enable_hcall(kvm_state, H_CLEAR_MOD);
+}
+
 void kvmppc_set_papr(PowerPCCPU *cpu)
 {
     CPUState *cs = CPU(cpu);

target-ppc/kvm_ppc.h

@@ -24,6 +24,7 @@ int kvmppc_get_hypercall(CPUPPCState *env, uint8_t *buf, int buf_len);
 int kvmppc_set_interrupt(PowerPCCPU *cpu, int irq, int level);
 void kvmppc_enable_logical_ci_hcalls(void);
 void kvmppc_enable_set_mode_hcall(void);
+void kvmppc_enable_clear_ref_mod_hcalls(void);
 void kvmppc_set_papr(PowerPCCPU *cpu);
 int kvmppc_set_compat(PowerPCCPU *cpu, uint32_t cpu_version);
 void kvmppc_set_mpic_proxy(PowerPCCPU *cpu, int mpic_proxy);
@@ -113,6 +114,10 @@ static inline void kvmppc_enable_set_mode_hcall(void)
 {
 }
 
+static inline void kvmppc_enable_clear_ref_mod_hcalls(void)
+{
+}
+
 static inline void kvmppc_set_papr(PowerPCCPU *cpu)
 {
 }