Re: [PATCH v2 2/2] Documentation/hw-vuln: Document the interaction between IBRS and STIBP

KP Singh
2023-02-24T03:30:43Z

On Thu, Feb 23, 2023 at 9:52 AM Borislav Petkov <bp@alien8.de> wrote:
>
> On Tue, Feb 21, 2023 at 07:49:08PM +0100, KP Singh wrote:
> > ... Consequently, STIBP needs to be explicitly
> > + enabled to guard against cross-thread attacks in userspace.
>
> needs?
>
> That sounds like something the user needs to do. But we do it by
> default. Let's rephrase:
>
> "Systems which support enhanced IBRS (eIBRS) enable IBRS protections once at
> boot and they're automatically protected against Spectre v2 variant
> attacks, including cross-thread branch target injections on SMT systems
> (STIBP). IOW, eIBRS enables STIBP too.
>
> Legacy IBRS systems clear the IBRS bit on exit to userspace and
> therefore explicitly enable STIBP for that."

ack, I will respin both patches with your suggestions.

- KP

>
> Simple.
>
> --
> Regards/Gruss,
> Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette