[PATCH V4 01/10] accel/kvm: Extract common KVM vCPU {creation, parking} code

[Salil Mehta]

KVM vCPU creation is done once during the initialization of the VM when Qemu
thread is spawned. This is common to all the architectures.

Hot-unplug of vCPU results in destruction of the vCPU object in QOM but the
corresponding KVM vCPU object in the Host KVM is not destroyed and its
representative KVM vCPU object/context in Qemu is parked.

Refactor common logic so that some APIs could be reused by vCPU Hotplug code.

Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
---
 accel/kvm/kvm-all.c    | 64 ++++++++++++++++++++++++++++++++----------
 accel/kvm/trace-events |  4 +++
 include/sysemu/kvm.h   | 16 +++++++++++
 3 files changed, 69 insertions(+), 15 deletions(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index ff1578bb32..0dcaa15276 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -137,6 +137,7 @@ static QemuMutex kml_slots_lock;
 #define kvm_slots_unlock()  qemu_mutex_unlock(&kml_slots_lock)
 
 static void kvm_slot_init_dirty_bitmap(KVMSlot *mem);
+static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id);
 
 static inline void kvm_resample_fd_remove(int gsi)
 {
@@ -320,14 +321,53 @@ err:
     return ret;
 }
 
+void kvm_park_vcpu(CPUState *cpu)
+{
+    struct KVMParkedVcpu *vcpu;
+
+    trace_kvm_park_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
+
+    vcpu = g_malloc0(sizeof(*vcpu));
+    vcpu->vcpu_id = kvm_arch_vcpu_id(cpu);
+    vcpu->kvm_fd = cpu->kvm_fd;
+    QLIST_INSERT_HEAD(&kvm_state->kvm_parked_vcpus, vcpu, node);
+}
+
+int kvm_create_vcpu(CPUState *cpu)
+{
+    unsigned long vcpu_id = kvm_arch_vcpu_id(cpu);
+    KVMState *s = kvm_state;
+    int kvm_fd;
+
+    trace_kvm_create_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
+
+    /* check if the KVM vCPU already exist but is parked */
+    kvm_fd = kvm_get_vcpu(s, vcpu_id);
+    if (kvm_fd < 0) {
+        /* vCPU not parked: create a new KVM vCPU */
+        kvm_fd = kvm_vm_ioctl(s, KVM_CREATE_VCPU, vcpu_id);
+        if (kvm_fd < 0) {
+            error_report("KVM_CREATE_VCPU IOCTL failed for vCPU %lu", vcpu_id);
+            return kvm_fd;
+        }
+    }
+
+    cpu->kvm_fd = kvm_fd;
+    cpu->kvm_state = s;
+    cpu->vcpu_dirty = true;
+    cpu->dirty_pages = 0;
+    cpu->throttle_us_per_full = 0;
+
+    return 0;
+}
+
 static int do_kvm_destroy_vcpu(CPUState *cpu)
 {
     KVMState *s = kvm_state;
     long mmap_size;
-    struct KVMParkedVcpu *vcpu = NULL;
     int ret = 0;
 
-    DPRINTF("kvm_destroy_vcpu\n");
+    trace_kvm_destroy_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
 
     ret = kvm_arch_destroy_vcpu(cpu);
     if (ret < 0) {
@@ -353,10 +393,7 @@ static int do_kvm_destroy_vcpu(CPUState *cpu)
         }
     }
 
-    vcpu = g_malloc0(sizeof(*vcpu));
-    vcpu->vcpu_id = kvm_arch_vcpu_id(cpu);
-    vcpu->kvm_fd = cpu->kvm_fd;
-    QLIST_INSERT_HEAD(&kvm_state->kvm_parked_vcpus, vcpu, node);
+    kvm_park_vcpu(cpu);
 err:
     return ret;
 }
@@ -377,6 +414,8 @@ static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id)
         if (cpu->vcpu_id == vcpu_id) {
             int kvm_fd;
 
+            trace_kvm_get_vcpu(vcpu_id);
+
             QLIST_REMOVE(cpu, node);
             kvm_fd = cpu->kvm_fd;
             g_free(cpu);
@@ -384,7 +423,7 @@ static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id)
         }
     }
 
-    return kvm_vm_ioctl(s, KVM_CREATE_VCPU, (void *)vcpu_id);
+    return -ENOENT;
 }
 
 int kvm_init_vcpu(CPUState *cpu, Error **errp)
@@ -395,19 +434,14 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)
 
     trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
 
-    ret = kvm_get_vcpu(s, kvm_arch_vcpu_id(cpu));
+    ret = kvm_create_vcpu(cpu);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "kvm_init_vcpu: kvm_get_vcpu failed 
(%lu)",
+        error_setg_errno(errp, -ret,
+                         "kvm_init_vcpu: kvm_create_vcpu failed (%lu)",
                          kvm_arch_vcpu_id(cpu));
         goto err;
     }
 
-    cpu->kvm_fd = ret;
-    cpu->kvm_state = s;
-    cpu->vcpu_dirty = true;
-    cpu->dirty_pages = 0;
-    cpu->throttle_us_per_full = 0;
-
     mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0);
     if (mmap_size < 0) {
         ret = mmap_size;
diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events
index 399aaeb0ec..08e2dc253f 100644
--- a/accel/kvm/trace-events
+++ b/accel/kvm/trace-events
@@ -9,6 +9,10 @@ kvm_device_ioctl(int fd, int type, void *arg) "dev fd %d, type 
0x%x, arg %p"
 kvm_failed_reg_get(uint64_t id, const char *msg) "Warning: Unable to retrieve 
ONEREG %" PRIu64 " from KVM: %s"
 kvm_failed_reg_set(uint64_t id, const char *msg) "Warning: Unable to set 
ONEREG %" PRIu64 " to KVM: %s"
 kvm_init_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d id: %lu"
+kvm_create_vcpu(int cpu_index, unsigned long arch_cpu_id) "creating KVM cpu: 
cpu_index: %d arch vcpu-id: %lu"
+kvm_get_vcpu(unsigned long arch_cpu_id) "unparking KVM vcpu: arch vcpu-id: %lu"
+kvm_destroy_vcpu(int cpu_index, unsigned long arch_cpu_id) "destroy vcpu: 
cpu_index: %d arch vcpu-id: %lu"
+kvm_park_vcpu(int cpu_index, unsigned long arch_cpu_id) "parking KVM vcpu: 
cpu_index: %d arch vcpu-id: %lu"
 kvm_irqchip_commit_routes(void) ""
 kvm_irqchip_add_msi_route(char *name, int vector, int virq) "dev %s vector %d 
virq %d"
 kvm_irqchip_update_msi_route(int virq) "Updating MSI route virq=%d"
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index ee9025f8e9..740686ab60 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -465,6 +465,22 @@ void kvm_set_sigmask_len(KVMState *s, unsigned int 
sigmask_len);
 int kvm_physical_memory_addr_from_host(KVMState *s, void *ram_addr,
                                        hwaddr *phys_addr);
 
+/**
+ * kvm_create_vcpu - Gets a parked KVM vCPU or creates a KVM vCPU
+ * @cpu: QOM CPUState object for which KVM vCPU has to be fetched/created.
+ *
+ * @returns: 0 when success, errno (<0) when failed.
+ */
+int kvm_create_vcpu(CPUState *cpu);
+
+/**
+ * kvm_park_vcpu - Park Qemu KVM vCPU context
+ * @cpu: QOM CPUState object for which Qemu KVM vCPU context has to be parked.
+ *
+ * @returns: none
+ */
+void kvm_park_vcpu(CPUState *cpu);
+
 #endif /* NEED_CPU_H */
 
 void kvm_cpu_synchronize_state(CPUState *cpu);
-- 
2.34.1