[Qemu-devel] [PATCH v4 3/5] spapr: Implement H_CONFER

[Nicholas Piggin]

This does not do directed yielding and is not quite as strict as PAPR
specifies in terms of precise dispatch behaviour. This generally will
mean suboptimal performance, rather than guest misbehaviour. Linux
does not rely on exact dispatch behaviour.

Signed-off-by: Nicholas Piggin <address@hidden>
---
 hw/ppc/spapr_hcall.c | 48 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
index 8b208ab259..28d58113be 100644
--- a/hw/ppc/spapr_hcall.c
+++ b/hw/ppc/spapr_hcall.c
@@ -1069,6 +1069,53 @@ static target_ulong h_cede(PowerPCCPU *cpu, 
SpaprMachineState *spapr,
     return H_SUCCESS;
 }
 
+static target_ulong h_confer(PowerPCCPU *cpu, SpaprMachineState *spapr,
+                           target_ulong opcode, target_ulong *args)
+{
+    target_long target = args[0];
+    uint32_t dispatch = args[1];
+    PowerPCCPU *target_cpu = spapr_find_cpu(target);
+    CPUState *target_cs = CPU(target_cpu);
+    CPUState *cs = CPU(cpu);
+    SpaprCpuState *spapr_cpu;
+
+    /*
+     * This does not do a targeted yield or confer, but check the parameter
+     * anyway. -1 means confer to all/any other CPUs.
+     */
+    if (target != -1 && !target_cs) {
+        return H_PARAMETER;
+    }
+
+    spapr_cpu = spapr_cpu_state(target_cpu);
+
+    /*
+     * PAPR specifies waiting until proded in this case, without dispatch
+     * counter check.
+     */
+    if (cpu == target_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;
+    }
+
+    if (spapr_cpu->dispatch_counter != dispatch || (dispatch & 1) == 0) {
+        return H_SUCCESS;
+    }
+
+    cs->exception_index = EXCP_YIELD;
+    cpu_loop_exit(cs);
+
+    return H_SUCCESS;
+}
+
 static target_ulong h_prod(PowerPCCPU *cpu, SpaprMachineState *spapr,
                            target_ulong opcode, target_ulong *args)
 {
@@ -1909,6 +1956,7 @@ static void hypercall_register_types(void)
     /* hcall-splpar */
     spapr_register_hypercall(H_REGISTER_VPA, h_register_vpa);
     spapr_register_hypercall(H_CEDE, h_cede);
+    spapr_register_hypercall(H_CONFER, h_confer);
     spapr_register_hypercall(H_PROD, h_prod);
 
     spapr_register_hypercall(H_SIGNAL_SYS_RESET, h_signal_sys_reset);
-- 
2.20.1