RE: [PATCH V15 1/7] accel/kvm: Extract common KVM vCPU {creation,parking} code

[Salil Mehta]

>  From: Igor Mammedov <imammedo@redhat.com>
>  Sent: Monday, July 15, 2024 2:28 PM
>  To: Salil Mehta <salil.mehta@huawei.com>
>  
>  On Mon, 15 Jul 2024 14:49:25 +0200
>  Igor Mammedov <imammedo@redhat.com> wrote:
>  
>  > On Sat, 13 Jul 2024 19:25:10 +0100
>  > Salil Mehta <salil.mehta@huawei.com> wrote:
>  >
>  > > KVM vCPU creation is done once during the vCPU realization when Qemu
>  > > vCPU thread is spawned. This is common to all the architectures as of  
> now.
>  > >
>  > > 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 as KVM doesn't support vCPU removal. Therefore, its
>  > > representative KVM vCPU object/context in Qemu is parked.
>  > >
>  > > Refactor architecture common logic so that some APIs could be reused
>  > > by vCPU Hotplug code of some architectures likes ARM, Loongson etc.
>  > > Update new/old APIs with trace events. New APIs
>  > > qemu_{create,park,unpark}_vcpu() can be externally called. No
>  functional change is intended here.
>  > >
>  > > 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>
>  > > Tested-by: Miguel Luis <miguel.luis@oracle.com>
>  > > Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
>  > > Reviewed-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
>  > > Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
>  > > Tested-by: Zhao Liu <zhao1.liu@intel.com>
>  > > Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
>  > > Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
>  >
>  > Reviewed-by: Igor Mammedov <imammedo@redhat.com>
>  
>  this needs fixing, to make checkpatch happy
>  
>  Checking 0001-accel-kvm-Extract-common-KVM-vCPU-creation-parking-
>  c.patch...
>  WARNING: line over 80 characters
>  #120: FILE: accel/kvm/kvm-all.c:368:
>  +    trace_kvm_unpark_vcpu(vcpu_id, kvm_fd > 0 ? "unparked" : "not found
>  + parked");


Thanks. I will fix this as well.


>  
>  total: 0 errors, 1 warnings, 183 lines checked
>  
>  >
>  > > ---
>  > >  accel/kvm/kvm-all.c    | 95 ++++++++++++++++++++++++++++----------
>  ----
>  > >  accel/kvm/kvm-cpus.h   |  1 -
>  > >  accel/kvm/trace-events |  5 ++-
>  > >  include/sysemu/kvm.h   | 25 +++++++++++
>  > >  4 files changed, 92 insertions(+), 34 deletions(-)
>  > >
>  > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index
>  > > 2b4ab89679..e446d18944 100644
>  > > --- a/accel/kvm/kvm-all.c
>  > > +++ b/accel/kvm/kvm-all.c
>  > > @@ -340,14 +340,71 @@ 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_unpark_vcpu(KVMState *s, unsigned long vcpu_id) {
>  > > +    struct KVMParkedVcpu *cpu;
>  > > +    int kvm_fd = -ENOENT;
>  > > +
>  > > +    QLIST_FOREACH(cpu, &s->kvm_parked_vcpus, node) {
>  > > +        if (cpu->vcpu_id == vcpu_id) {
>  > > +            QLIST_REMOVE(cpu, node);
>  > > +            kvm_fd = cpu->kvm_fd;
>  > > +            g_free(cpu);
>  > > +        }
>  > > +    }
>  > > +
>  > > +    trace_kvm_unpark_vcpu(vcpu_id, kvm_fd > 0 ? "unparked" : "not
>  > > + found parked");
>  > > +
>  > > +    return kvm_fd;
>  > > +}
>  > > +
>  > > +int kvm_create_vcpu(CPUState *cpu)
>  > > +{
>  > > +    unsigned long vcpu_id = kvm_arch_vcpu_id(cpu);
>  > > +    KVMState *s = kvm_state;
>  > > +    int kvm_fd;
>  > > +
>  > > +    /* check if the KVM vCPU already exist but is parked */
>  > > +    kvm_fd = kvm_unpark_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;
>  > > +
>  > > +    trace_kvm_create_vcpu(cpu->cpu_index, vcpu_id, kvm_fd);
>  > > +
>  > > +    return 0;
>  > > +}
>  > > +
>  > >  static int do_kvm_destroy_vcpu(CPUState *cpu)  {
>  > >      KVMState *s = kvm_state;
>  > >      long mmap_size;
>  > > -    struct KVMParkedVcpu *vcpu = NULL;
>  > >      int ret = 0;
>  > >
>  > > -    trace_kvm_destroy_vcpu();
>  > > +    trace_kvm_destroy_vcpu(cpu->cpu_index,
>  kvm_arch_vcpu_id(cpu));
>  > >
>  > >      ret = kvm_arch_destroy_vcpu(cpu);
>  > >      if (ret < 0) {
>  > > @@ -373,10 +430,7 @@ 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;
>  > >  }
>  > > @@ -389,24 +443,6 @@ void kvm_destroy_vcpu(CPUState *cpu)
>  > >      }
>  > >  }
>  > >
>  > > -static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id) -{
>  > > -    struct KVMParkedVcpu *cpu;
>  > > -
>  > > -    QLIST_FOREACH(cpu, &s->kvm_parked_vcpus, node) {
>  > > -        if (cpu->vcpu_id == vcpu_id) {
>  > > -            int kvm_fd;
>  > > -
>  > > -            QLIST_REMOVE(cpu, node);
>  > > -            kvm_fd = cpu->kvm_fd;
>  > > -            g_free(cpu);
>  > > -            return kvm_fd;
>  > > -        }
>  > > -    }
>  > > -
>  > > -    return kvm_vm_ioctl(s, KVM_CREATE_VCPU, (void *)vcpu_id);
>  > > -}
>  > > -
>  > >  int kvm_init_vcpu(CPUState *cpu, Error **errp)  {
>  > >      KVMState *s = kvm_state;
>  > > @@ -415,19 +451,14 @@ 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/kvm-cpus.h b/accel/kvm/kvm-cpus.h index
>  > > ca40add32c..171b22fd29 100644
>  > > --- a/accel/kvm/kvm-cpus.h
>  > > +++ b/accel/kvm/kvm-cpus.h
>  > > @@ -22,5 +22,4 @@ bool kvm_supports_guest_debug(void);  int
>  > > kvm_insert_breakpoint(CPUState *cpu, int type, vaddr addr, vaddr
>  > > len);  int kvm_remove_breakpoint(CPUState *cpu, int type, vaddr
>  > > addr, vaddr len);  void kvm_remove_all_breakpoints(CPUState *cpu);
>  > > -
>  > >  #endif /* KVM_CPUS_H */
>  > > diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events index
>  > > 681ccb667d..37626c1ac5 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, int
>  kvm_fd) "index: %d, id: %lu, kvm fd: %d"
>  > > +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_unpark_vcpu(unsigned long arch_cpu_id, const char *msg) "id:
>  %lu %s"
>  > >  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"
>  > > @@ -25,7 +29,6 @@ kvm_dirty_ring_reaper(const char *s) "%s"
>  > >  kvm_dirty_ring_reap(uint64_t count, int64_t t) "reaped %"PRIu64"
>  pages (took %"PRIi64" us)"
>  > >  kvm_dirty_ring_reaper_kick(const char *reason) "%s"
>  > >  kvm_dirty_ring_flush(int finished) "%d"
>  > > -kvm_destroy_vcpu(void) ""
>  > >  kvm_failed_get_vcpu_mmap_size(void) ""
>  > >  kvm_cpu_exec(void) ""
>  > >  kvm_interrupt_exit_request(void) ""
>  > > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h index
>  > > c31d9c7356..c4a914b3d8 100644
>  > > --- a/include/sysemu/kvm.h
>  > > +++ b/include/sysemu/kvm.h
>  > > @@ -313,6 +313,31 @@ int kvm_create_device(KVMState *s, uint64_t
>  type, bool test);
>  > >   */
>  > >  bool kvm_device_supported(int vmfd, uint64_t type);
>  > >
>  > > +/**
>  > > + * 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);
>  > > +
>  > > +/**
>  > > + * kvm_unpark_vcpu - unpark QEMU KVM vCPU context
>  > > + * @s: KVM State
>  > > + * @vcpu_id: Architecture vCPU ID of the parked vCPU
>  > > + *
>  > > + * @returns: KVM fd
>  > > + */
>  > > +int kvm_unpark_vcpu(KVMState *s, unsigned long vcpu_id);
>  > > +
>  > >  /* Arch specific hooks */
>  > >
>  > >  extern const KVMCapabilityInfo kvm_arch_required_capabilities[];
>  >
>