kvm: add support for -machine kernel_irqchip=split

This patch adds the initial plumbing for split IRQ chip mode via
KVM_CAP_SPLIT_IRQCHIP. In addition to option processing, a number of
kvm_*_in_kernel macros are defined to help clarify which component is
where.
Signed-off-by: NMatt Gingell <gingell@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/core/machine.c

@@ -11,6 +11,7 @@
  */
 
 #include "hw/boards.h"
+#include "qapi-visit.h"
 #include "qapi/visitor.h"
 #include "hw/sysbus.h"
 #include "sysemu/sysemu.h"
@@ -31,12 +32,39 @@ static void machine_set_accel(Object *obj, const char *value, Error **errp)
     ms->accel = g_strdup(value);
 }
 
-static void machine_set_kernel_irqchip(Object *obj, bool value, Error **errp)
+static void machine_set_kernel_irqchip(Object *obj, Visitor *v,
+                                       void *opaque, const char *name,
+                                       Error **errp)
 {
+    Error *err = NULL;
     MachineState *ms = MACHINE(obj);
+    OnOffSplit mode;
 
-    ms->kernel_irqchip_allowed = value;
-    ms->kernel_irqchip_required = value;
+    visit_type_OnOffSplit(v, &mode, name, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    } else {
+        switch (mode) {
+        case ON_OFF_SPLIT_ON:
+            ms->kernel_irqchip_allowed = true;
+            ms->kernel_irqchip_required = true;
+            ms->kernel_irqchip_split = false;
+            break;
+        case ON_OFF_SPLIT_OFF:
+            ms->kernel_irqchip_allowed = false;
+            ms->kernel_irqchip_required = false;
+            ms->kernel_irqchip_split = false;
+            break;
+        case ON_OFF_SPLIT_SPLIT:
+            ms->kernel_irqchip_allowed = true;
+            ms->kernel_irqchip_required = true;
+            ms->kernel_irqchip_split = true;
+            break;
+        default:
+            abort();
+        }
+    }
 }
 
 static void machine_get_kvm_shadow_mem(Object *obj, Visitor *v,
@@ -341,12 +369,12 @@ static void machine_initfn(Object *obj)
     object_property_set_description(obj, "accel",
                                     "Accelerator list",
                                     NULL);
-    object_property_add_bool(obj, "kernel-irqchip",
-                             NULL,
-                             machine_set_kernel_irqchip,
-                             NULL);
+    object_property_add(obj, "kernel-irqchip", "OnOffSplit",
+                        NULL,
+                        machine_set_kernel_irqchip,
+                        NULL, NULL, NULL);
     object_property_set_description(obj, "kernel-irqchip",
-                                    "Use KVM in-kernel irqchip",
+                                    "Configure KVM in-kernel irqchip",
                                     NULL);
     object_property_add(obj, "kvm-shadow-mem", "int",
                         machine_get_kvm_shadow_mem,
@@ -472,6 +500,11 @@ bool machine_kernel_irqchip_required(MachineState *machine)
     return machine->kernel_irqchip_required;
 }
 
+bool machine_kernel_irqchip_split(MachineState *machine)
+{
+    return machine->kernel_irqchip_split;
+}
+
 int machine_kvm_shadow_mem(MachineState *machine)
 {
     return machine->kvm_shadow_mem;

hw/i386/pc_piix.c

@@ -53,6 +53,7 @@
 #include "hw/xen/xen_pt.h"
 #endif
 #include "migration/migration.h"
+#include "kvm_i386.h"
 
 #define MAX_IDE_BUS 2
 

include/hw/boards.h

@@ -35,6 +35,7 @@ extern MachineState *current_machine;
 bool machine_usb(MachineState *machine);
 bool machine_kernel_irqchip_allowed(MachineState *machine);
 bool machine_kernel_irqchip_required(MachineState *machine);
+bool machine_kernel_irqchip_split(MachineState *machine);
 int machine_kvm_shadow_mem(MachineState *machine);
 int machine_phandle_start(MachineState *machine);
 bool machine_dump_guest_core(MachineState *machine);
@@ -111,6 +112,7 @@ struct MachineState {
     char *accel;
     bool kernel_irqchip_allowed;
     bool kernel_irqchip_required;
+    bool kernel_irqchip_split;
     int kvm_shadow_mem;
     char *dtb;
     char *dumpdtb;

include/sysemu/kvm.h

@@ -43,6 +43,7 @@
 
 extern bool kvm_allowed;
 extern bool kvm_kernel_irqchip;
+extern bool kvm_split_irqchip;
 extern bool kvm_async_interrupts_allowed;
 extern bool kvm_halt_in_kernel_allowed;
 extern bool kvm_eventfds_allowed;
@@ -70,6 +71,16 @@ extern bool kvm_ioeventfd_any_length_allowed;
  */
 #define kvm_irqchip_in_kernel() (kvm_kernel_irqchip)
 
+/**
+ * kvm_irqchip_is_split:
+ *
+ * Returns: true if the user asked us to split the irqchip
+ * implementation between user and kernel space. The details are
+ * architecture and machine specific. On PC, it means that the PIC,
+ * IOAPIC, and PIT are in user space while the LAPIC is in the kernel.
+ */
+#define kvm_irqchip_is_split() (kvm_split_irqchip)
+
 /**
  * kvm_async_interrupts_enabled:
  *

qapi/common.json

@@ -115,3 +115,19 @@
 ##
 { 'enum': 'OnOffAuto',
   'data': [ 'auto', 'on', 'off' ] }
+
+##
+# @OnOffSplit
+#
+# An enumeration of three values: on, off, and split
+#
+# @on: Enabled
+#
+# @off: Disabled
+#
+# @split: Mixed
+#
+# Since: 2.6
+##
+{ 'enum': 'OnOffSplit',
+  'data': [ 'on', 'off', 'split' ] }

qemu-options.hx

@@ -33,6 +33,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
     "                property accel=accel1[:accel2[:...]] selects accelerator\n"
     "                supported accelerators are kvm, xen, tcg (default: tcg)\n"
     "                kernel_irqchip=on|off controls accelerated irqchip support\n"
+    "                kernel_irqchip=on|off|split controls accelerated irqchip support (default=off)\n"
     "                vmport=on|off|auto controls emulation of vmport (default: auto)\n"
     "                kvm_shadow_mem=size of KVM shadow MMU\n"
     "                dump-guest-core=on|off include guest memory in a core dump (default=on)\n"
@@ -55,7 +56,7 @@ kvm, xen, or tcg can be available. By default, tcg is used. If there is more
 than one accelerator specified, the next one is used if the previous one fails
 to initialize.
 @item kernel_irqchip=on|off
-Enables in-kernel irqchip support for the chosen accelerator when available.
+Controls in-kernel irqchip support for the chosen accelerator when available.
 @item gfx_passthru=on|off
 Enables IGD GFX passthrough support for the chosen machine when available.
 @item vmport=on|off|auto