Re: [Xen-devel] [PATCH v2 1/7] x86: Add support for STAC/CLAC instructions

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.04.14 at 12:02, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 25/04/14 09:51, Wu, Feng wrote:
>>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>>>>>> On 23.04.14 at 14:32, <feng.wu@xxxxxxxxx> wrote:
>>>>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>>>>>>>> On 23.04.14 at 16:34, <feng.wu@xxxxxxxxx> wrote:
>>>>>> +#define ASM_STAC(prefix) ASM_AC(__ASM_STAC, prefix)
>>>>>> +#define ASM_CLAC(prefix) ASM_AC(__ASM_CLAC, prefix)
>>>>> What is "prefix" good for here, i.e. why can't you put the % right
>>>>> in the macro?
>>>> Because this macro will be used in the basic inline assembly (use "%" as 
>>>> the
>>>> register prefix)
>>>> and extended assembly (use "%%" as the register prefix).
>>> Perhaps worth avoiding the basic uses then, by converting them to
>>> extended? Passing these % or %% to the macro looks rather ugly,
>>> so if the suggestion isn't viable, some other trick can certainly be
>>> found to avoid this.
>> Need to add CLAC in the beginning of interrupt in the following macro, which 
> uses
>> the basic inline assembly, seems it is hard to convert this one to extended 
> format. I
>> have been thinking about this for some time and tried several method, but I 
> am kind of
>> run out of ideas about it. Jan, do you have any suggestion about this?
> 
> What do you mean about "basic" and "extended" format ?

The ones respectively without and with inputs/outputs/clobbers.

Jan


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