Re: [Xen-devel] [PATCH] x86: re-enable VCPUOP_register_vcpu_time_memory_area

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.05.13 at 11:44, Keir Fraser <keir.xen@xxxxxxxxx> wrote:
> On 16/05/2013 09:47, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> 
>> By moving the call to update_vcpu_system_time() out of schedule() into
>> arch-specific context switch code, the original problem of the function
>> accessing the wrong domain's address space goes away (obvious even from
>> patch context, as update_runstate_area() does similar copying).
>> 
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Acked-by: Keir Fraser <keir@xxxxxxx>
> 
>> ---
>> Regardless of the code freeze I'd still like to propose this for
>> inclusion in 4.3, mainly based on the fact that this got disabled late
>> in the 4.0 release cycle with the expectation that it would get
>> re-enabled soon after. Now that upstream Linux also has, as of 3.8 at
>> least on x86-64, the necessary hypervisor independent support code, it
>> would be odd to not leverage this on Xen.

George?

>> --- a/xen/arch/arm/domain.c
>> +++ b/xen/arch/arm/domain.c
>> @@ -232,6 +232,9 @@ static void schedule_tail(struct vcpu *p
>>  
>>      if ( prev != current )
>>          update_runstate_area(current);
>> +
>> +    /* Ensure that the vcpu has an up-to-date time base. */
>> +    update_vcpu_system_time(current);
>>  }
>>  
>>  static void continue_new_vcpu(struct vcpu *prev)
>> --- a/xen/arch/x86/domain.c
>> +++ b/xen/arch/x86/domain.c
>> @@ -966,11 +966,6 @@ arch_do_vcpu_op(
>>  
>>      switch ( cmd )
>>      {
>> -    /*
>> -     * XXX Disable for 4.0.0: __update_vcpu_system_time() writes to the 
> given
>> -     * virtual address even when running in another domain's address space.
>> -     */
>> -#if 0
>>      case VCPUOP_register_vcpu_time_memory_area:
>>      {
>>          struct vcpu_register_time_memory_area area;
>> @@ -989,7 +984,6 @@ arch_do_vcpu_op(
>>  
>>          break;
>>      }
>> -#endif
>>  
>>      case VCPUOP_get_physid:
>>      {
>> @@ -1457,6 +1451,9 @@ void context_switch(struct vcpu *prev, s
>>      if (prev != next)
>>          update_runstate_area(next);
>>  
>> +    /* Ensure that the vcpu has an up-to-date time base. */
>> +    update_vcpu_system_time(next);
>> +
>>      schedule_tail(next);
>>      BUG();
>>  }
>> --- a/xen/arch/x86/hvm/hvm.c
>> +++ b/xen/arch/x86/hvm/hvm.c
>> @@ -3174,6 +3174,7 @@ static long hvm_vcpu_op(
>>      case VCPUOP_set_singleshot_timer:
>>      case VCPUOP_stop_singleshot_timer:
>>      case VCPUOP_register_vcpu_info:
>> +    case VCPUOP_register_vcpu_time_memory_area:
>>          rc = do_vcpu_op(cmd, vcpuid, arg);
>>          break;
>>      default:
>> @@ -3232,6 +3233,7 @@ static long hvm_vcpu_op_compat32(
>>      case VCPUOP_set_singleshot_timer:
>>      case VCPUOP_stop_singleshot_timer:
>>      case VCPUOP_register_vcpu_info:
>> +    case VCPUOP_register_vcpu_time_memory_area:
>>          rc = compat_vcpu_op(cmd, vcpuid, arg);
>>          break;
>>      default:
>> --- a/xen/common/schedule.c
>> +++ b/xen/common/schedule.c
>> @@ -1231,8 +1231,6 @@ static void schedule(void)
>>      if ( next_slice.migrated )
>>          evtchn_move_pirqs(next);
>>  
>> -    /* Ensure that the domain has an up-to-date time base. */
>> -    update_vcpu_system_time(next);
>>      vcpu_periodic_timer_work(next);
>>  
>>      context_switch(prev, next);
>> 
>> 
>> 




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