Date: Sat, 17 Feb 2018 11:47:26 -0800 From: Jeremy Chadwick <jdc@koitsu.org> To: freebsd-stable@freebsd.org Subject: stable/11 r329462 - Meltdown/Spectre MFC questions Message-ID: <20180217194726.GA79666@icarus.home.lan>
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Reference: https://svnweb.freebsd.org/base?view=revision&revision=329462 Do the following new loader tunables and sysctls have documentation anywhere? I ask because I wish to know how to turn all of this off (yes you heard me correctly), as not all systems necessarily require mitigation of these flaws. Best I can tell from skimming source: vm.pmap.pti - Description: Page Table Isolation enabled - Loader tunable, visible in sysctl (read-only) - Integer - Default value: depends on CPU model and capabilities, see function pti_get_default(); looks like AMD = 0, any CPU with RDCL_NO capability enabled = 0, else 1 hw.ibrs_active - Description: Indirect Branch Restricted Speculation active - sysctl (read-only) - Integer - Real-time indicator as to if IBRS is currently on or off hw.ibrs_disable - Description: Disable Indirect Branch Restricted Speculation - Loader tunable and sysctl tunable (read-write) - Integer - Default value: unsure. Variable declaration has 1 but SYSCTL_PROC() macro has 0. Thank you. -- | Jeremy Chadwick jdc@koitsu.org | | UNIX Systems Administrator http://jdc.koitsu.org/ | | Making life hard for others since 1977. PGP 4BD6C0CB |
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