Messages in this thread | | | Subject | Re: [PATCH v1] x86/retpoline: Use lfence in the retpoline/RSB filling RSB macros | From | Tom Lendacky <> | Date | Sat, 13 Jan 2018 15:13:45 -0600 |
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On 1/13/2018 8:07 AM, Van De Ven, Arjan wrote: >>> The RSB filling macro is applicable to AMD, and, if software is unable to >>> verify that lfence is serializing on AMD (possible when running under a >>> hypervisor), the generic retpoline support will be used and, so, is also >>> applicable to AMD. Change the use of pause to lfence. >>> >>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> >> >> Conditionally-Acked-by: David Woodhouse <dwmw@amazon.co.uk> > > > pause is technically the "save me power" instruction > > how about a compromise where we do a double: > > pause > lfence > jmp <up> > > as sequence... that way if the branch recovery is fast, we get the performance of pause, but if it takes a while, on AMD you get the behavior of lfence?
That should work on AMD.
Thanks, Tom
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