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Subject: Re: [PATCH v3 01/13] x86/retpoline: Add initial retpoline support
To: Paul Turner <pjt@google.com>, David Woodhouse <dwmw2@infradead.org>
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 5 Jan 2018 12:26:27 +0100
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On 05/01/2018 11:28, Paul Turner wrote:
> 
> The "pause; jmp" sequence proved minutely faster than "lfence;jmp" which is why
> it was chosen.
> 
>   "pause; jmp" 33.231 cycles/call 9.517 ns/call
>   "lfence; jmp" 33.354 cycles/call 9.552 ns/call

Do you have timings for a non-retpolined indirect branch with the
predictor suppressed via IBRS=1?  So at least we can compute the break
even point.

Paolo