On Thu, 2009-06-18 at 01:06 +0800, H. Peter Anvin wrote:
> Ingo Molnar wrote:
> >>
> >> +static inline int kernel_fpu_using(void)
> >> +{
> >> + if (in_interrupt() && !(read_cr0() & X86_CR0_TS))
> >> + return 1;
> >> + return 0;
> >> +}
> >> +
> >
> > Looks sane to me. Herbert, do you ack it?
> >
>
> Although I have to say, the structure of:
>
> if (boolean test)
> return 1;
> return 0;
>
> ... truly was hit with the ugly stick. It really should be:
>
> static inline bool kernel_fpu_using(void)
> {
> return in_interrupt() && !(read_cr0() && C86_CR0_TS);
> }
Yes. This is better. I will change this.
> Huang: if I recall correctly, these functions were originally designed
> to deal with the fact that VIA processors generate spurious #TS faults
> due to broken design of the Padlock instructions. The AES and PCLMUL
> instructions actually use SSE registers and so will require different
> structure.
They are a little different. VIA want to make sure that they can deal
with spurious #TS faults, while AES and PCLMUL need to check whether
MMX/SSE registers are available.
After some thinking, I think something as follow may be more
appropriate:
/* This may be useful for someone else */
static inline bool fpu_using(void)
{
return !(read_cr0() & X86_CR0_TS);
}
static inline bool irq_fpu_using(void)
{
return in_interrupt() && fpu_using();
}
Best Regards,
Huang Ying
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