kvm: Introduce kvm_arch_get_default_type hook

kvm_arch_get_default_type() returns the default KVM type. This hook is
particularly useful to derive a KVM type that is valid for "none"
machine model, which is used by libvirt to probe the availability of
KVM.

For MIPS, the existing mips_kvm_type() is reused. This function ensures
the availability of VZ which is mandatory to use KVM on the current
QEMU.

Cc: qemu-stable@nongnu.org
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-id: 20230727073134.134102-2-akihiko.odaki@daynix.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: added doc comment for new function]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

accel/kvm/kvm-all.c

@@ -2458,7 +2458,7 @@ static int kvm_init(MachineState *ms)
     KVMState *s;
     const KVMCapabilityInfo *missing_cap;
     int ret;
-    int type = 0;
+    int type;
     uint64_t dirty_log_manual_caps;
 
     qemu_mutex_init(&kml_slots_lock);
@@ -2523,6 +2523,8 @@ static int kvm_init(MachineState *ms)
         type = mc->kvm_type(ms, kvm_type);
     } else if (mc->kvm_type) {
         type = mc->kvm_type(ms, NULL);
+    } else {
+        type = kvm_arch_get_default_type(ms);
     }
 
     do {

hw/mips/loongson3_virt.c

@@ -29,7 +29,6 @@
 #include "qemu/datadir.h"
 #include "qapi/error.h"
 #include "elf.h"
-#include "kvm_mips.h"
 #include "hw/char/serial.h"
 #include "hw/intc/loongson_liointc.h"
 #include "hw/mips/mips.h"
@@ -612,7 +611,6 @@ static void loongson3v_machine_class_init(ObjectClass *oc, void *data)
     mc->max_cpus = LOONGSON_MAX_VCPUS;
     mc->default_ram_id = "loongson3.highram";
     mc->default_ram_size = 1600 * MiB;
-    mc->kvm_type = mips_kvm_type;
     mc->minimum_page_bits = 14;
     mc->default_nic = "virtio-net-pci";
 }

include/sysemu/kvm.h

@@ -369,6 +369,8 @@ int kvm_arch_get_registers(CPUState *cpu);
 
 int kvm_arch_put_registers(CPUState *cpu, int level);
 
+int kvm_arch_get_default_type(MachineState *ms);
+
 int kvm_arch_init(MachineState *ms, KVMState *s);
 
 int kvm_arch_init_vcpu(CPUState *cpu);

target/arm/kvm.c

@@ -247,6 +247,11 @@ int kvm_arm_get_max_vm_ipa_size(MachineState *ms, bool *fixed_ipa)
     return ret > 0 ? ret : 40;
 }
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     int ret = 0;

target/i386/kvm/kvm.c

@@ -2556,6 +2556,11 @@ static void register_smram_listener(Notifier *n, void *unused)
                                  &smram_address_space, 1, "kvm-smram");
 }
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     uint64_t identity_base = 0xfffbc000;

target/mips/kvm.c

@@ -1266,7 +1266,7 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
     abort();
 }
 
-int mips_kvm_type(MachineState *machine, const char *vm_type)
+int kvm_arch_get_default_type(MachineState *machine)
 {
 #if defined(KVM_CAP_MIPS_VZ)
     int r;

target/mips/kvm_mips.h

@@ -25,13 +25,4 @@ void kvm_mips_reset_vcpu(MIPSCPU *cpu);
 int kvm_mips_set_interrupt(MIPSCPU *cpu, int irq, int level);
 int kvm_mips_set_ipi_interrupt(MIPSCPU *cpu, int irq, int level);
 
-#ifdef CONFIG_KVM
-int mips_kvm_type(MachineState *machine, const char *vm_type);
-#else
-static inline int mips_kvm_type(MachineState *machine, const char *vm_type)
-{
-    return 0;
-}
-#endif
-
 #endif /* KVM_MIPS_H */

target/ppc/kvm.c

@@ -108,6 +108,11 @@ static int kvm_ppc_register_host_cpu_type(void);
 static void kvmppc_get_cpu_characteristics(KVMState *s);
 static int kvmppc_get_dec_bits(void);
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     cap_interrupt_unset = kvm_check_extension(s, KVM_CAP_PPC_UNSET_IRQ);

target/riscv/kvm.c

@@ -914,6 +914,11 @@ int kvm_arch_add_msi_route_post(struct kvm_irq_routing_entry *route,
     return 0;
 }
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     return 0;

target/s390x/kvm/kvm.c

@@ -340,6 +340,11 @@ static void ccw_machine_class_foreach(ObjectClass *oc, void *opaque)
     mc->default_cpu_type = S390_CPU_TYPE_NAME("host");
 }
 
+int kvm_arch_get_default_type(MachineState *ms)
+{
+    return 0;
+}
+
 int kvm_arch_init(MachineState *ms, KVMState *s)
 {
     object_class_foreach(ccw_machine_class_foreach, TYPE_S390_CCW_MACHINE,