Re: [Xen-devel] [PATCH] replace bogus -ENOSYS uses

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 11/08/16 19:10, Andrew Cooper wrote:
> On 09/08/16 11:40, Jan Beulich wrote:
>> --- a/xen/arch/x86/cpu/mtrr/main.c
>> +++ b/xen/arch/x86/cpu/mtrr/main.c
>> @@ -332,7 +332,7 @@ int mtrr_add_page(unsigned long base, un
>>      if ((type == MTRR_TYPE_WRCOMB) && !have_wrcomb()) {
>>              printk(KERN_WARNING
>>                     "mtrr: your processor doesn't support 
>> write-combining\n");
>> -            return -ENOSYS;
>> +            return -EOPNOTSUPP;
> 
> Will this break the classic-xen MTRR code?  ISTR it was very picky, from
> the cpuid work.  Also, as some further cleanup, that printk should
> become a print-once.
> 
> The others look ok.

That does bring up a good general point though -- the return value is
part of the ABI.  Are you reasonably confident that none of the callers
will be confused when this return value changes?  If so, a note in the
commit message justifying this confidence would be helpful I think.

 -George


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