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

[Igor Mammedov <imammedo@redhat.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");

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[];  
>