Re: [PATCH] kvm: kvm_init_vcpu take Error pointer

[Philippe Mathieu-Daudé]

On 7/23/20 6:09 PM, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Clean up the error handling in kvm_init_vcpu so we can see what went
> wrong more easily.
> 
> Make it take an Error ** and fill it out with what failed, including
> the cpu id, so you can tell if it only fails at a given ID.
> 
> Replace the remaining DPRINTF by a trace.
> 
> This turns a:
> kvm_init_vcpu failed: Invalid argument
> 
> into:
> kvm_init_vcpu: kvm_get_vcpu failed (256): Invalid argument
> 
> and with the trace you then get to see:
> 
> 19049@1595520414.310107:kvm_init_vcpu index: 169 id: 212
> 19050@1595520414.310635:kvm_init_vcpu index: 170 id: 256
> qemu-system-x86_64: kvm_init_vcpu: kvm_get_vcpu failed (256): Invalid argument
> 
> which makes stuff a lot more obvious.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>  accel/kvm/kvm-all.c    | 19 ++++++++++++++-----
>  accel/kvm/trace-events |  1 +
>  accel/stubs/kvm-stub.c |  2 +-
>  include/sysemu/kvm.h   |  2 +-
>  softmmu/cpus.c         |  6 +-----
>  5 files changed, 18 insertions(+), 12 deletions(-)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 63ef6af9a1c..0fbece977c7 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -430,17 +430,18 @@ static int kvm_get_vcpu(KVMState *s, unsigned long 
> vcpu_id)
>      return kvm_vm_ioctl(s, KVM_CREATE_VCPU, (void *)vcpu_id);
>  }
>  
> -int kvm_init_vcpu(CPUState *cpu)
> +int kvm_init_vcpu(CPUState *cpu, Error **errp)
>  {
>      KVMState *s = kvm_state;
>      long mmap_size;
>      int ret;
>  
> -    DPRINTF("kvm_init_vcpu\n");
> +    trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
>  
>      ret = kvm_get_vcpu(s, kvm_arch_vcpu_id(cpu));
>      if (ret < 0) {
> -        DPRINTF("kvm_create_vcpu failed\n");
> +        error_setg_errno(errp, -ret, "kvm_init_vcpu: kvm_get_vcpu failed 
> (%lu)",
> +                         kvm_arch_vcpu_id(cpu));
>          goto err;
>      }
>  
> @@ -451,7 +452,8 @@ int kvm_init_vcpu(CPUState *cpu)
>      mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0);
>      if (mmap_size < 0) {
>          ret = mmap_size;
> -        DPRINTF("KVM_GET_VCPU_MMAP_SIZE failed\n");
> +        error_setg_errno(errp, -mmap_size,
> +                         "kvm_init_vcpu: KVM_GET_VCPU_MMAP_SIZE failed");
>          goto err;
>      }
>  
> @@ -459,7 +461,9 @@ int kvm_init_vcpu(CPUState *cpu)
>                          cpu->kvm_fd, 0);
>      if (cpu->kvm_run == MAP_FAILED) {
>          ret = -errno;
> -        DPRINTF("mmap'ing vcpu state failed\n");
> +        error_setg_errno(errp, ret,
> +                         "kvm_init_vcpu: mmap'ing vcpu state failed (%lu)",
> +                         kvm_arch_vcpu_id(cpu));
>          goto err;
>      }
>  
> @@ -469,6 +473,11 @@ int kvm_init_vcpu(CPUState *cpu)
>      }
>  
>      ret = kvm_arch_init_vcpu(cpu);
> +    if (ret < 0) {
> +        error_setg_errno(errp, -ret,
> +                         "kvm_init_vcpu: kvm_arch_init_vcpu failed (%lu)",
> +                         kvm_arch_vcpu_id(cpu));
> +    }
>  err:
>      return ret;
>  }
> diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events
> index a68eb665343..e15ae8980d3 100644
> --- a/accel/kvm/trace-events
> +++ b/accel/kvm/trace-events
> @@ -8,6 +8,7 @@ kvm_run_exit(int cpu_index, uint32_t reason) "cpu_index %d, 
> reason %d"
>  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_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/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c
> index 82f118d2df9..cd573bfe3d9 100644
> --- a/accel/stubs/kvm-stub.c
> +++ b/accel/stubs/kvm-stub.c
> @@ -37,7 +37,7 @@ int kvm_destroy_vcpu(CPUState *cpu)
>      return -ENOSYS;
>  }
>  
> -int kvm_init_vcpu(CPUState *cpu)
> +int kvm_init_vcpu(CPUState *cpu, Error **errp)
>  {
>      return -ENOSYS;
>  }
> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> index b4174d941c2..410848af514 100644
> --- a/include/sysemu/kvm.h
> +++ b/include/sysemu/kvm.h
> @@ -216,7 +216,7 @@ int kvm_has_many_ioeventfds(void);
>  int kvm_has_gsi_routing(void);
>  int kvm_has_intx_set_mask(void);
>  
> -int kvm_init_vcpu(CPUState *cpu);
> +int kvm_init_vcpu(CPUState *cpu, Error **errp);
>  int kvm_cpu_exec(CPUState *cpu);
>  int kvm_destroy_vcpu(CPUState *cpu);
>  
> diff --git a/softmmu/cpus.c b/softmmu/cpus.c
> index a802e899abb..9725fd9951f 100644
> --- a/softmmu/cpus.c
> +++ b/softmmu/cpus.c
> @@ -1170,11 +1170,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
>      cpu->can_do_io = 1;
>      current_cpu = cpu;
>  
> -    r = kvm_init_vcpu(cpu);
> -    if (r < 0) {
> -        error_report("kvm_init_vcpu failed: %s", strerror(-r));
> -        exit(1);
> -    }
> +    kvm_init_vcpu(cpu, &error_fatal);
>  
>      kvm_init_cpu_signals(cpu);
>  
>