Messages in this thread | | | Date | Sun, 28 Oct 2018 10:32:38 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [Patch v3 03/13] x86/speculation: Add static key for Enhanced IBRS |
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On Fri, 26 Oct 2018, Tim Chen wrote: > On 10/26/2018 09:58 AM, Waiman Long wrote: > >> @@ -386,6 +389,7 @@ static void __init spectre_v2_select_mitigation(void) > >> /* Force it so VMEXIT will restore correctly */ > >> x86_spec_ctrl_base |= SPEC_CTRL_IBRS; > >> wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); > >> + static_branch_enable(&spectre_v2_enhanced_ibrs); > >> goto specv2_set_mode; > >> } > >> if (IS_ENABLED(CONFIG_RETPOLINE)) > > > > Why you need a static key for enhanced IBRS? It is supposed to be set at > > boot time and never get changed after that. It will be easier to use a > > feature bit for that instead. We usually use static key when the value > > can be changed at run time. > > > > We're close to running out of the feature bits. So I'm trying not to > use those.
Software feature bits can be extended when needed. That's really a non issue.
Thanks,
tglx
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