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

[Markus Armbruster]

Igor Mammedov <address@hidden> writes:

> 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.

I'm blind.  Can you suggest a potential reproducer for me to try?

>>      /*
>>       * 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);