Re: [patch 2.6.13-rc3a] i386: inline restore_fpu

[Chuck Ebbert <76306.1226@compuserve.com>]

On Date: Fri, 22 Jul 2005 at 16:19:25 -0700 (PDT), Linus Torvalds wrote:

>       /*
>        * The "nop" is needed to make the instructions the same
>        * length.
>        */
>       #define restore_fpu(tsk)                        \
>               alternative_input(                      \
>                       "nop ; frstor %1",              \
>                       "fxrstor %1",                   \
>                       X86_FEATURE_FXSR,               \
>                       "m" ((tsk)->thread.i387.fsave))

   Probably a very minor point, but shouldn't it be

                        "m" ((tsk)->thread.i387.fxsave))

because that's the largest possible operand that could end up being read?


> Now, we should do the same for "fnsave ; fwait" vs "fxsave ; fnclex" too,
> but I was lazy. If somebody wants to try that, it would need an 
> "alternative_output()" define but should otherwise be trivial too.

  Is that function called __save_init_fpu because it saves and then
initializes the fpu?  Unlike fsave, fxsave does not init the fpu after
it saves the state; to make the behavior match it should be "fxsave ; fninit"


__
Chuck