spapr: Implement H_JOIN

This has been useful to modify and test the Linux pseries suspend
code but it requires modification to the guest to call it (due to
being gated by other unimplemented features). It is not otherwise
used by Linux yet, but work is slowly progressing there.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Message-Id: <20190718034214.14948-5-npiggin@gmail.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr.c

@@ -1070,6 +1070,7 @@ static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)
     add_str(hypertas, "hcall-tce");
     add_str(hypertas, "hcall-vio");
     add_str(hypertas, "hcall-splpar");
+    add_str(hypertas, "hcall-join");
     add_str(hypertas, "hcall-bulk");
     add_str(hypertas, "hcall-set-mode");
     add_str(hypertas, "hcall-sprg0");

hw/ppc/spapr_hcall.c

@@ -1070,6 +1070,62 @@ static target_ulong h_cede(PowerPCCPU *cpu, SpaprMachineState *spapr,
     return H_SUCCESS;
 }
 
+/*
+ * Confer to self, aka join. Cede could use the same pattern as well, if
+ * EXCP_HLT can be changed to ECXP_HALTED.
+ */
+static target_ulong h_confer_self(PowerPCCPU *cpu)
+{
+    CPUState *cs = CPU(cpu);
+    SpaprCpuState *spapr_cpu = spapr_cpu_state(cpu);
+
+    if (spapr_cpu->prod) {
+        spapr_cpu->prod = false;
+        return H_SUCCESS;
+    }
+    cs->halted = 1;
+    cs->exception_index = EXCP_HALTED;
+    cs->exit_request = 1;
+
+    return H_SUCCESS;
+}
+
+static target_ulong h_join(PowerPCCPU *cpu, SpaprMachineState *spapr,
+                           target_ulong opcode, target_ulong *args)
+{
+    CPUPPCState *env = &cpu->env;
+    CPUState *cs;
+    bool last_unjoined = true;
+
+    if (env->msr & (1ULL << MSR_EE)) {
+        return H_BAD_MODE;
+    }
+
+    /*
+     * Must not join the last CPU running. Interestingly, no such restriction
+     * for H_CONFER-to-self, but that is probably not intended to be used
+     * when H_JOIN is available.
+     */
+    CPU_FOREACH(cs) {
+        PowerPCCPU *c = POWERPC_CPU(cs);
+        CPUPPCState *e = &c->env;
+        if (c == cpu) {
+            continue;
+        }
+
+        /* Don't have a way to indicate joined, so use halted && MSR[EE]=0 */
+        if (!cs->halted || (e->msr & (1ULL << MSR_EE))) {
+            last_unjoined = false;
+            break;
+        }
+    }
+    if (last_unjoined) {
+        return H_CONTINUE;
+    }
+
+    return h_confer_self(cpu);
+}
+
 static target_ulong h_confer(PowerPCCPU *cpu, SpaprMachineState *spapr,
                            target_ulong opcode, target_ulong *args)
 {
@@ -1090,26 +1146,15 @@ static target_ulong h_confer(PowerPCCPU *cpu, SpaprMachineState *spapr,
             return H_PARAMETER;
         }
 
-        spapr_cpu = spapr_cpu_state(target_cpu);
-
         /*
          * target == self is a special case, we wait until prodded, without
          * dispatch counter check.
          */
         if (cpu == target_cpu) {
-            if (spapr_cpu->prod) {
+            return h_confer_self(cpu);
-                spapr_cpu->prod = false;
-
-                return H_SUCCESS;
-            }
-
-            cs->halted = 1;
-            cs->exception_index = EXCP_HALTED;
-            cs->exit_request = 1;
-
-            return H_SUCCESS;
         }
 
+        spapr_cpu = spapr_cpu_state(target_cpu);
         if (!spapr_cpu->vpa_addr || ((dispatch & 1) == 0)) {
             return H_SUCCESS;
         }
@@ -1984,6 +2029,9 @@ static void hypercall_register_types(void)
     spapr_register_hypercall(H_CONFER, h_confer);
     spapr_register_hypercall(H_PROD, h_prod);
 
+    /* hcall-join */
+    spapr_register_hypercall(H_JOIN, h_join);
+
     spapr_register_hypercall(H_SIGNAL_SYS_RESET, h_signal_sys_reset);
 
     /* processor register resource access h-calls */