Re: [Qemu-devel] [PATCH 1/2] vl: Fix to create accel compat props before migration object again

[Igor Mammedov]

On Wed, 27 Mar 2019 16:03:46 +0100
Markus Armbruster <address@hidden> wrote:

> Recent commit cda4aa9a5a0 moved block backend creation before machine
> property evaluation.  This broke block backends registering migration
> blockers.  Commit e60483f2f84 fixed it by moving migration object
> creation before block backend creation.  This broke migration with
> Xen.  Turns out we need to configure the accelerator before we create
> the migration object so that Xen's accelerator compat properties get
> applied.  Fix by calling configure_accelerator() earlier, right before
> migration_object_init().
> 
> Fixes: e60483f2f8498ae08ae79ca4c6fb03a3317f5e1e
> Reported-by: Anthony PERARD <address@hidden>
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  vl.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/vl.c b/vl.c
> index d61d5604e5..28b9e9a170 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -4276,6 +4276,12 @@ int main(int argc, char **argv, char **envp)
>          exit(0);
>      }
>  
> +    /*
> +     * Must run before migration_object_init() to make Xen's
> +     * accelerator compat properties stick
> +     */
> +    configure_accelerator(current_machine, argv[0]);
> +
Setting machine properties with this change happens after
accelerator was initialized.

It probably will break initialization of accelerator features
(to name a couple kernel-irqchip, memory-encryption) that depend
on machine properties being set before accelerator is initialized.

>      /*
>       * Migration object can only be created after global properties
>       * are applied correctly.
> @@ -4297,8 +4303,6 @@ int main(int argc, char **argv, char **envp)
>      current_machine->maxram_size = maxram_size;
>      current_machine->ram_slots = ram_slots;
>  
> -    configure_accelerator(current_machine, argv[0]);
> -
>      if (!qtest_enabled() && machine_class->deprecation_reason) {
>          error_report("Machine type '%s' is deprecated: %s",
>                       machine_class->name, machine_class->deprecation_reason);