Messages in this thread | | | Subject | Re: [RFC 6/7] x86: Move kernel_fpu_using to asm/i387.h | From | Huang Ying <> | Date | Thu, 18 Jun 2009 09:57:48 +0800 |
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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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