On Wed, 21 Nov 2018, Tim Chen wrote: > Commit 53c613fe "x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation" > turns on STIBP all the time. > > This causes large performance regression in many workloads. > > One case is perlbench in the SpecInt Rate 2006 test suite which shows a > 21% reduction in throughput. > There're also other reports of drop in performance on Python and PHP benchmarks: > https://www.phoronix.com/scan.php?page=article&item=linux-420-bisect&num=2 > > STIBP on all the time should not be the default option. > > Turn off STIBP all the time for now till STIBP can be applied on > a per task basis. > > Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> > --- > arch/x86/kernel/cpu/bugs.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c > index c37e66e..21a8f39 100644 > --- a/arch/x86/kernel/cpu/bugs.c > +++ b/arch/x86/kernel/cpu/bugs.c > @@ -332,7 +332,7 @@ static bool stibp_needed(void) > if (!boot_cpu_has(X86_FEATURE_STIBP)) > return false; > > - return true; > + return false; > } For -stable, which actually makes it to production, I already asked Greg to drop it. For -rc, I don't think we need to do this at this moment, given the prctl+seccomp fixup is basically ready, do we? Thanks, -- Jiri Kosina SUSE Labs
