diff mbox series

[V6,1/9] accel/kvm: Extract common KVM vCPU {creation, parking} code

Message ID 20231013105129.25648-2-salil.mehta@huawei.com (mailing list archive)
State New, archived
Headers show
Series Add architecture agnostic code to support vCPU Hotplug | expand

Commit Message

Salil Mehta Oct. 13, 2023, 10:51 a.m. UTC
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.
Update new/old APIs with trace events instead of DTRACE.

Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Xianglai Li <lixianglai@loongson.cn>
---
 accel/kvm/kvm-all.c    | 64 ++++++++++++++++++++++++++++++++----------
 accel/kvm/trace-events |  4 +++
 include/sysemu/kvm.h   | 16 +++++++++++
 3 files changed, 69 insertions(+), 15 deletions(-)

Comments

Igor Mammedov Oct. 27, 2023, 12:56 p.m. UTC | #1
On Fri, 13 Oct 2023 11:51:21 +0100
Salil Mehta <salil.mehta@huawei.com> wrote:

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

is it really true fox x86?

> 
> 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
                                                                ^
since KVM doesn't support vCPU removal

> representative KVM vCPU object/context in Qemu is parked.
> 
> Refactor common logic so that some APIs could be reused by vCPU Hotplug code.
'reused' part doesn't happen within this series. So a reason
why patch exists is not clear/no one can deduce the reason
without the actual user here.

Suggest to move it to a series that actually will use this patch.


> Update new/old APIs with trace events instead of DTRACE.
> 
> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Tested-by: Xianglai Li <lixianglai@loongson.cn>
> ---
>  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 72e1d1141c..bfa7816aaa 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..cdd0c95c09 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) "index: %d id: %lu"
> +kvm_get_vcpu(unsigned long arch_cpu_id) "id: %lu"
> +kvm_destroy_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d id: %lu"
> +kvm_park_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d 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..8137e6a44c 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);
Salil Mehta Nov. 6, 2023, 2:37 p.m. UTC | #2
Hi Igor,
Thanks for the review comments. I was bit on and off so could not address
the comments. Please find my replies inline.

> From: Igor Mammedov <imammedo@redhat.com>
> Sent: Friday, October 27, 2023 1:57 PM
> To: Salil Mehta <salil.mehta@huawei.com>
> Cc: qemu-devel@nongnu.org; qemu-arm@nongnu.org; maz@kernel.org; jean-
> philippe@linaro.org; Jonathan Cameron <jonathan.cameron@huawei.com>;
> lpieralisi@kernel.org; peter.maydell@linaro.org;
> richard.henderson@linaro.org; andrew.jones@linux.dev; david@redhat.com;
> philmd@linaro.org; eric.auger@redhat.com; oliver.upton@linux.dev;
> pbonzini@redhat.com; mst@redhat.com; will@kernel.org; gshan@redhat.com;
> rafael@kernel.org; alex.bennee@linaro.org; linux@armlinux.org.uk;
> darren@os.amperecomputing.com; ilkka@os.amperecomputing.com;
> vishnu@os.amperecomputing.com; karl.heubaum@oracle.com;
> miguel.luis@oracle.com; salil.mehta@opnsrc.net; zhukeqian
> <zhukeqian1@huawei.com>; wangxiongfeng (C) <wangxiongfeng2@huawei.com>;
> wangyanan (Y) <wangyanan55@huawei.com>; jiakernel2@gmail.com;
> maobibo@loongson.cn; lixianglai@loongson.cn; Linuxarm <linuxarm@huawei.com>
> Subject: Re: [PATCH V6 1/9] accel/kvm: Extract common KVM vCPU
> {creation,parking} code
> 
> On Fri, 13 Oct 2023 11:51:21 +0100
> Salil Mehta <salil.mehta@huawei.com> wrote:
> 
> > KVM vCPU creation is done once during the initialization of the VM when Qemu
>                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > thread is spawned. This is common to all the architectures.
> 
> is it really true fox x86?

Thanks for pointing out. I just meant,

"KVM vCPU creation is done once either during VM initialization or during
vCPU realization during Hotplug...."


> > 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
>                                                                 ^
> since KVM doesn't support vCPU removal

Correct. Will add.


> > representative KVM vCPU object/context in Qemu is parked.
> >
> > Refactor common logic so that some APIs could be reused by vCPU Hotplug code.
> 'reused' part doesn't happen within this series. So a reason
> why patch exists is not clear/no one can deduce the reason
> without the actual user here.
> 
> Suggest to move it to a series that actually will use this patch.


I can do that but I think Loongson guys might need bit of this logic
as well. This patch also brings a good restructuring to the existing
code and fixes the traces etc.

I would humbly suggest to keep it unless you have strong views.

Thanks
Salil.

> > Update new/old APIs with trace events instead of DTRACE.
> >
> > Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> > Reviewed-by: Gavin Shan <gshan@redhat.com>
> > Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Tested-by: Xianglai Li <lixianglai@loongson.cn>
> > ---
> >  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 72e1d1141c..bfa7816aaa 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..cdd0c95c09 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) "index: %d id:
> %lu"
> > +kvm_get_vcpu(unsigned long arch_cpu_id) "id: %lu"
> > +kvm_destroy_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d
> id: %lu"
> > +kvm_park_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d 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..8137e6a44c 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);
diff mbox series

Patch

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 72e1d1141c..bfa7816aaa 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..cdd0c95c09 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) "index: %d id: %lu"
+kvm_get_vcpu(unsigned long arch_cpu_id) "id: %lu"
+kvm_destroy_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d id: %lu"
+kvm_park_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d 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..8137e6a44c 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);