Re: [PATCH 4/5] xen/memory: Fix acquire_resource size semantics

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 31/07/2020 15:44, Jan Beulich wrote:
> On 28.07.2020 13:37, Andrew Cooper wrote:
>> @@ -1026,19 +1047,6 @@ static int acquire_resource(
>>      if ( xmar.pad != 0 )
>>          return -EINVAL;
>>  
>> -    if ( guest_handle_is_null(xmar.frame_list) )
>> -    {
>> -        if ( xmar.nr_frames )
>> -            return -EINVAL;
>> -
>> -        xmar.nr_frames = ARRAY_SIZE(mfn_list);
>> -
>> -        if ( __copy_field_to_guest(arg, &xmar, nr_frames) )
>> -            return -EFAULT;
>> -
>> -        return 0;
>> -    }
>> -
>>      if ( xmar.nr_frames > ARRAY_SIZE(mfn_list) )
>>          return -E2BIG;
> While arguably minor, the error code in the null-handle case
> would imo better be the same, no matter how big xmar.nr_frames
> is.

This clause doesn't survive the fixes to batching.

Given how broken this infrastructure is, I'm not concerned with
transient differences in error codes for users which will ultimately
fail anyway.

~Andrew