Re: [tip:x86/fpu] x86-64, asm: Use fxsaveq/fxrestorq in more places

[Linus Torvalds]

On Fri, Oct 22, 2010 at 6:20 PM, tip-bot for H. Peter Anvin
<hpa@xxxxxxxxx> wrote:
>
> Checkin d7acb92fea932ad2e7846480aeacddc2c03c8485 made use of fxsaveq
> in fpu_fxsave() if the assembler supports it; this adds
> fxsaveq/fxrstorq to fxrstor_checking() and fxsave_user() as well.

Hmm. I really think you should be able to do something like this

  #ifdef CONFIG_AS_FXSAVEQ
    #define FXSAVEQ_INSN "fxsaveq %[fx]"
    #define FXRSTORQ_INSN "fxrstorq %[fx]"
    #define FX_EXTRA(ptr)
  #else
    #define FXSAVEQ_INSN "rex64/fxsave (%[fxr])"
    #define FXRSTORQ_INSN "rex64/fxrstor (%[fxr])"
    #define FX_EXTRA(ptr)  [fxr] "R" (ptr)
  #endif

and then you should be able to write the actual code something like

   asm volatile(FXSAVEQ_INSN
      :[fx] "=m" (memory)
      :FX_EXTRA(&memory))

and

  #define __COMMA_CONCAT(x) ,##x
  #define COMMA_CONCAT(x) __COMMA_CONCAT(x)
  asm volatile(FXRSTRORQ_INSN
      : :[fx] "m" (memory) COMMA_CONCAT(FX_EXTRA(&memory)));

or something like that (obviously you'll need the exception stuff too there).

With no #ifdef's in the actual code. Hmm?

                                      Linus
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