On Tue, Feb 25, 2025 at 02:40:24PM -0800, Sean Christopherson wrote: > On Tue, Feb 25, 2025, Yosry Ahmed wrote: > > February 25, 2025 at 11:49 AM, "Sean Christopherson" <seanjc@xxxxxxxxxx> wrote: > > > > > > On Wed, Feb 19, 2025, Yosry Ahmed wrote: > > > > > > > > Instead of using X86_FEATURE_USE_IBPB to guard the IBPB execution in the > > > > vCPU load path, introduce a static branch, similar to switch_mm_*_ibpb. > > > > > > > > This makes it obvious in spectre_v2_user_select_mitigation() what > > > > exactly is being toggled, instead of the unclear X86_FEATURE_USE_IBPB > > > > (which will be shortly removed). It also provides more fine-grained > > > > control, making it simpler to change/add paths that control the IBPB in > > > > the vCPU load path without affecting other IBPBs. > > > > > > > > Signed-off-by: Yosry Ahmed <yosry.ahmed@xxxxxxxxx> > > > > > > > > --- > > > > > > > > arch/x86/include/asm/nospec-branch.h | 2 ++ > > > > arch/x86/kernel/cpu/bugs.c | 5 +++++ > > > > arch/x86/kvm/svm/svm.c | 2 +- > > > > arch/x86/kvm/vmx/vmx.c | 2 +- > > > > 4 files changed, 9 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h > > > > index 7cbb76a2434b9..a22836c5fb338 100644 > > > > --- a/arch/x86/include/asm/nospec-branch.h > > > > +++ b/arch/x86/include/asm/nospec-branch.h > > > > @@ -552,6 +552,8 @@ DECLARE_STATIC_KEY_FALSE(switch_to_cond_stibp); > > > > DECLARE_STATIC_KEY_FALSE(switch_mm_cond_ibpb); > > > > > > DECLARE_STATIC_KEY_FALSE(switch_mm_always_ibpb); > > > > > > +DECLARE_STATIC_KEY_FALSE(vcpu_load_ibpb); > > > > > > > > > > How about ibpb_on_vcpu_load? To make it easy for readers to understand exactly > > > what the knob controls. > > > > I was trying to remain consistent with the existing static branches' names, > > but I am fine with ibpb_on_vcpu_load if others don't object. > > I assumed as much :-) I'm ok with vcpu_load_ibpb if that's what others prefer. To be honest looking at this again I think I prefer consistency, so if you don't mind and others don't chime in I'd rather keep it as-is. Alternatively I can rename all the static branches (e.g. ibpb_always_on_switch_mm) :P
