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SubjectRe: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation
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On Tue, 2018-01-23 at 11:15 +0100, Ingo Molnar wrote:
>
> BTW., the reason this is enabled on all distro kernels is because the overhead is 
> a single patched-in NOP instruction in the function epilogue, when tracing is 
> disabled. So it's not even a CALL+RET - it's a patched in NOP.

Hm? We still have GCC emitting 'call __fentry__' don't we? Would be
nice to get to the point where we can patch *that* out into a NOP... or
are you saying we already can?

But this is a digression. I was being pedantic about the "0 cycles" but
sure, this would be perfectly tolerable.[unhandled content-type:application/x-pkcs7-signature]
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