On Fri, Jan 05, 2018 at 07:12:12PM -0800, Dave Hansen wrote: > On 01/05/2018 06:12 PM, Tim Chen wrote: > > .macro ENABLE_IBRS > > - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > > + testl $1, dynamic_ibrs > > + jz .Lskip_\@ > > There was an earlier suggestion to use STATIC_JUMP_IF_... here. That's
Yes, and thanks for Cc'ing me... :/ > a good suggestion, but we encountered some issues with it either > crashing the kernel at boot or not properly turning on/off. > > We would love to do that minor really soon, but we figured everyone > would rather see this version than wait for us to debug such a minor tweak. Its not minor, you need that LFENCE without it. Which makes the whole thing unconditionally expensive, which sucks.
