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Date: Wed, 10 Jan 2018 15:22:35 -0800 (PST)
From: David Lang <david@lang.hm>
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To: David Woodhouse <dwmw@amazon.co.uk>
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Subject: Re: [PATCH] x86/retpoline: Fill return stack buffer on vmexit
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I somewhat hate to ask this, but for those of us following at home, what does 
this add to the overhead?

I am remembering an estimate from mid last week that put retpoline at replacing 
a 3 clock 'ret' with 30 clocks of eye-bleed code