Messages in this thread | | | Date | Tue, 17 Mar 2015 10:47:50 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH RFC 0/2] x86/fpu: avoid "xstate_fault" in xsave_user/xrestore_user |
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On Mon, Mar 16, 2015 at 11:37:44PM +0100, Quentin Casasnovas wrote:
...
> __user_insn("btl [var2], %0 \n\t", > , /* no outputs, no need for dummy arg */ > SINGLE_ARG("r" (var1), [var2] "r" (var2)), /* two inputs */ > "cc");
So this becomes pretty unreadable IMO. And we shouldn't go nuts with optimizing this and sacrifice readability a lot.
TBH, I'd much prefer:
if (static_cpu_has_safe(X86_FEATURE_XSAVEOPT)) { check_insn(XSAVEOPT, ...); return; }
if (static_cpu_has_safe(X86_FEATURE_XSAVES)) { check_insn(XSAVES); return; }
check_insn(XSAVE, ...)
which is pretty clear.
We can even go a step further and add a static_cpu_has_safe thing which checks two features instead of one. The penalty we'd get is a single inconditional JMP which in the face of XSAVE* is nothing.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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