Messages in this thread | | | Date | Mon, 16 Mar 2015 15:57:42 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH RFC 0/2] x86/fpu: avoid "xstate_fault" in xsave_user/xrestore_user |
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On 03/16, Borislav Petkov wrote: > > On Sun, Mar 15, 2015 at 05:49:48PM +0100, Oleg Nesterov wrote: > > > > And I agree with Quentin, user_insn/check_insn can be improved to allow > > clobbers, more flexible "output", etc. But imo they already can make this > > code look a bit better, and "xstate_fault" must die eventually. > > FWIW, I did poke at that but there's still something wrong with my macros, will > take a look when I get a chance:
Sure, I won't argue if we use the new macros instead. But we already have check_insn/user_insn, why not use them?
For example,
> +#define XSTATE_XSAVE(st, lmask, hmask, err) \ > + asm volatile(ALTERNATIVE_2(XSAVE, \ > + XSAVEOPT, X86_FEATURE_XSAVEOPT, \ > + XSAVES, X86_FEATURE_XSAVES) \ > + "\n" \ > + ".pushsection .fixup,\"ax\"\n" \ > + "3: movl $-1, %[err]\n" \ > + "jmp " alt_end_marker "b\n" \ > + ".popsection\n" \ > + _ASM_EXTABLE(661b, 3b) \ > + : [err] "=r" (err) \ > + : "D" (st), "a" (lmask), "d" (hmask) \ > + : "memory") > +
to me check_insn(ALTERNATIVE_2(...)) looks better. Except we need the clobber. It is not easy to read the code like this, imo it would be better to avoid copy-and-paste and use the helpers we already have. Just we need to improve them.
But let me repeat, I leave this to you and others, I do not understand asm enough.
Oleg.
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