hjl.tools added a comment.

In D99708#2664218 <https://reviews.llvm.org/D99708#2664218>, @craig.topper 
wrote:

> In D99708#2664164 <https://reviews.llvm.org/D99708#2664164>, @hjl.tools wrote:
>
>> In D99708#2664076 <https://reviews.llvm.org/D99708#2664076>, @LuoYuanke 
>> wrote:
>>
>>> In D99708#2663989 <https://reviews.llvm.org/D99708#2663989>, @craig.topper 
>>> wrote:
>>>
>>>> A user interrupt is different than a regular interrupt right? It doesn't 
>>>> make sense that we would change the behavior of the interrupt calling 
>>>> convention just because the the user interrupt instructions are enabled. 
>>>> That would occur just from passing a -march for a newer CPU wouldn't it?
>>>
>>> Maybe need support another attribute "__attribute__ ((user_interrupt))" for 
>>> functions? However this is what gcc does 
>>> (https://gcc.godbolt.org/z/8ojTMG6bT).
>>
>> Since there won't be both user interrupt handler and kernel interrupt 
>> handler in the source, there is no need for another
>> attribute.   We discussed that kernel might need to use UINTR instructions.  
>> We decided that kernel could use inline asm
>> statements if needed.
>
> So if write kernel code and compile with -march=haswell today, I get IRET. If 
> tomorrow I change my command line to -march=sapphirerapids, now my kernel 
> interrupt code generates user interrupt instructions. That seems surprising.

-mcmodel=kernel should disable uiret.:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99870


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D99708/new/

https://reviews.llvm.org/D99708

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