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x86/spec_ctrl: Add 'nolfence' knob to disable fallback for spectre_v2 mitigation
authorKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Mon, 29 Jan 2018 18:08:20 +0000 (13:08 -0500)
committerJack Vogel <jack.vogel@oracle.com>
Thu, 1 Feb 2018 22:19:28 +0000 (14:19 -0800)
commit5ea301faa3cfe658171797fb5bf613c74edfe943
tree09f616e669217531a9f2314b06db2e26fb761504tree
parent5e86fd5926c37f8250b71d3d5b0be277edb7ddb9commit | diff
x86/spec_ctrl: Add 'nolfence' knob to disable fallback for spectre_v2 mitigation

If 'noibrs' is used, or the hardware does not have IBRS microcode
we fallback on using 'lfence' on every system call/interrupt/exception/etc.

This can dramatically slow down the performance. As a knob to
measure this provide 'nolfence' which will also disable this
security big hammer.

OraBug: 27472666
Reviewed-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Documentation/kernel-parameters.txt diff | blob | history
arch/x86/include/asm/spec_ctrl.h diff | blob | history
arch/x86/kernel/cpu/bugs_64.c diff | blob | history
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