On 19/08/2025 2:01 pm, Jan Beulich wrote:
> On 15.08.2025 22:41, Andrew Cooper wrote:
>> Right now they're inline in {read,write}_gs_shadow(), but we're going to need
>> to use these elsewhere to support FRED.
> But why "kern"? We're not dealing with GS in kernel / user terms, but in
> real / shadow ones.
Because it's a common name that also has the property of aligning nicely
when used beside GS_BASE.
But fine, I'll rename it.
> I'm also not quite happy with the double leading
> underscores, fwiw.
Consistency with the similar logic.
>
>> --- a/xen/arch/x86/include/asm/fsgsbase.h
>> +++ b/xen/arch/x86/include/asm/fsgsbase.h
>> @@ -32,6 +32,17 @@ static inline unsigned long __rdgsbase(void)
>> return base;
>> }
>>
>> +static inline unsigned long __rdgskern(void)
>> +{
>> + unsigned long base;
>> +
>> + asm_inline volatile ( "swapgs\n\t"
>> + "rdgsbase %0\n\t"
>> + "swapgs" : "=r" (base) );
> Again strictly speaking "=&r", if already you open-code rdgsbase() now.
As before, why? There are no inputs to be clobbered, early or otherwise.
~Andrew
