Re: [PATCH v2 01/11] accel/kvm: Check MachineClass kvm_type() return value

[Cornelia Huck <cohuck@xxxxxxxxxx>]

On Fri, 19 Feb 2021 18:38:37 +0100
Philippe Mathieu-Daudé <philmd@xxxxxxxxxx> wrote:

> MachineClass::kvm_type() can return -1 on failure.
> Document it, and add a check in kvm_init().
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
> ---
>  include/hw/boards.h | 3 ++-
>  accel/kvm/kvm-all.c | 6 ++++++
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index a46dfe5d1a6..68d3d10f6b0 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -127,7 +127,8 @@ typedef struct {
>   *    implement and a stub device is required.
>   * @kvm_type:
>   *    Return the type of KVM corresponding to the kvm-type string option or
> - *    computed based on other criteria such as the host kernel capabilities.
> + *    computed based on other criteria such as the host kernel capabilities
> + *    (which can't be negative), or -1 on error.
>   * @numa_mem_supported:
>   *    true if '--numa node.mem' option is supported and false otherwise
>   * @smp_parse:
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 84c943fcdb2..b069938d881 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -2057,6 +2057,12 @@ static int kvm_init(MachineState *ms)
>                                                              "kvm-type",
>                                                              &error_abort);
>          type = mc->kvm_type(ms, kvm_type);
> +        if (type < 0) {
> +            ret = -EINVAL;
> +            fprintf(stderr, "Failed to detect kvm-type for machine '%s'\n",
> +                    mc->name);
> +            goto err;
> +        }
>      }
>  
>      do {

No objection to this patch; but I'm wondering why some non-pseries
machines implement the kvm_type callback, when I see the kvm-type
property only for pseries? Am I holding my git grep wrong?