spapr: nested: register nested-hv api hcalls only for cap-nested-hv

Since cap-nested-hv is an optional capability, it makes sense to register
api specfic hcalls only when respective capability is enabled. This
requires to introduce a new API to unregister hypercalls to maintain
sanity across guest reboot since caps are re-applied across reboots and
re-registeration of hypercalls would hit assert otherwise.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

hw/ppc/spapr.c

@@ -1734,6 +1734,7 @@ static void spapr_machine_reset(MachineState *machine, ShutdownCause reason)
 
     pef_kvm_reset(machine->cgs, &error_fatal);
     spapr_caps_apply(spapr);
+    spapr_nested_reset(spapr);
 
     first_ppc_cpu = POWERPC_CPU(first_cpu);
     if (kvm_enabled() && kvmppc_has_cap_mmu_radix() &&

hw/ppc/spapr_hcall.c

@@ -1525,6 +1525,28 @@ void spapr_register_hypercall(target_ulong opcode, spapr_hcall_fn fn)
     *slot = fn;
 }
 
+void spapr_unregister_hypercall(target_ulong opcode)
+{
+    spapr_hcall_fn *slot;
+
+    if (opcode <= MAX_HCALL_OPCODE) {
+        assert((opcode & 0x3) == 0);
+
+        slot = &papr_hypercall_table[opcode / 4];
+    } else if (opcode >= SVM_HCALL_BASE && opcode <= SVM_HCALL_MAX) {
+        /* we only have SVM-related hcall numbers assigned in multiples of 4 */
+        assert((opcode & 0x3) == 0);
+
+        slot = &svm_hypercall_table[(opcode - SVM_HCALL_BASE) / 4];
+    } else {
+        assert((opcode >= KVMPPC_HCALL_BASE) && (opcode <= KVMPPC_HCALL_MAX));
+
+        slot = &kvmppc_hypercall_table[opcode - KVMPPC_HCALL_BASE];
+    }
+
+    *slot = NULL;
+}
+
 target_ulong spapr_hypercall(PowerPCCPU *cpu, target_ulong opcode,
                              target_ulong *args)
 {
@@ -1638,8 +1660,6 @@ static void hypercall_register_types(void)
     spapr_register_hypercall(KVMPPC_H_CAS, h_client_architecture_support);
 
     spapr_register_hypercall(KVMPPC_H_UPDATE_DT, h_update_dt);
-
-    spapr_register_nested();
 }
 
 type_init(hypercall_register_types)

hw/ppc/spapr_nested.c

@@ -7,6 +7,14 @@
 #include "hw/ppc/spapr_cpu_core.h"
 #include "hw/ppc/spapr_nested.h"
 
+void spapr_nested_reset(SpaprMachineState *spapr)
+{
+    if (spapr_get_cap(spapr, SPAPR_CAP_NESTED_KVM_HV)) {
+        spapr_unregister_nested_hv();
+        spapr_register_nested_hv();
+    }
+}
+
 #ifdef CONFIG_TCG
 #define PRTS_MASK      0x1f
 
@@ -375,20 +383,33 @@ void spapr_exit_nested(PowerPCCPU *cpu, int excp)
     address_space_unmap(CPU(cpu)->as, regs, len, len, true);
 }
 
-void spapr_register_nested(void)
+void spapr_register_nested_hv(void)
 {
     spapr_register_hypercall(KVMPPC_H_SET_PARTITION_TABLE, h_set_ptbl);
     spapr_register_hypercall(KVMPPC_H_ENTER_NESTED, h_enter_nested);
     spapr_register_hypercall(KVMPPC_H_TLB_INVALIDATE, h_tlb_invalidate);
     spapr_register_hypercall(KVMPPC_H_COPY_TOFROM_GUEST, h_copy_tofrom_guest);
 }
+
+void spapr_unregister_nested_hv(void)
+{
+    spapr_unregister_hypercall(KVMPPC_H_SET_PARTITION_TABLE);
+    spapr_unregister_hypercall(KVMPPC_H_ENTER_NESTED);
+    spapr_unregister_hypercall(KVMPPC_H_TLB_INVALIDATE);
+    spapr_unregister_hypercall(KVMPPC_H_COPY_TOFROM_GUEST);
+}
 #else
 void spapr_exit_nested(PowerPCCPU *cpu, int excp)
 {
     g_assert_not_reached();
 }
 
-void spapr_register_nested(void)
+void spapr_register_nested_hv(void)
+{
+    /* DO NOTHING */
+}
+
+void spapr_unregister_nested_hv(void)
 {
     /* DO NOTHING */
 }

include/hw/ppc/spapr.h

@@ -631,6 +631,7 @@ typedef target_ulong (*spapr_hcall_fn)(PowerPCCPU *cpu, SpaprMachineState *sm,
                                        target_ulong *args);
 
 void spapr_register_hypercall(target_ulong opcode, spapr_hcall_fn fn);
+void spapr_unregister_hypercall(target_ulong opcode);
 target_ulong spapr_hypercall(PowerPCCPU *cpu, target_ulong opcode,
                              target_ulong *args);
 
@@ -1028,5 +1029,8 @@ void spapr_vof_client_dt_finalize(SpaprMachineState *spapr, void *fdt);
 
 /* H_WATCHDOG */
 void spapr_watchdog_init(SpaprMachineState *spapr);
+void spapr_register_nested_hv(void);
+void spapr_unregister_nested_hv(void);
+void spapr_nested_reset(SpaprMachineState *spapr);
 
 #endif /* HW_SPAPR_H */

include/hw/ppc/spapr_nested.h

@@ -95,7 +95,6 @@ struct nested_ppc_state {
     int64_t tb_offset;
 };
 
-void spapr_register_nested(void);
 void spapr_exit_nested(PowerPCCPU *cpu, int excp);
 
 #endif /* HW_SPAPR_NESTED_H */