Messages in this thread | | | Subject | Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation | From | David Woodhouse <> | Date | Tue, 23 Jan 2018 10:27:24 +0000 |
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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] | |