Re: [PATCH v2 4/6] x86/bugs: Use a static branch to guard IBPB on vCPU switch

Sean Christopherson
2025-02-27T01:42:11Z

On Thu, Feb 27, 2025, Yosry Ahmed wrote:
> Instead of using X86_FEATURE_USE_IBPB to guard the IBPB execution in KVM
> when a new vCPU is loaded, 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 switch path without affecting other IBPBs.
>
> Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---

Acked-by: Sean Christopherson <seanjc@google.com>