Re: [PATCH RESEND] x86/speculation: Fix user-mode spectre-v2 protection with KERNEL_IBRS

[Borislav Petkov]

On Mon, Feb 20, 2023 at 10:56:38AM -0800, KP Singh wrote:
> Sure, it looks like an omission to me, we wrote a POC on Skylake that
> was able to do cross-thread training with the current set of
> mitigations.

Right.

> STIBP with IBRS is still correct if spectre_v2=ibrs had really meant
> IBRS everywhere,

Yeah, IBRS everywhere got shot down as a no-no very early in the game,
for apparent reasons.

> but just means KERNEL_IBRS, which means only kernel is protected,
> userspace is still unprotected.

Yes, that was always the intent with IBRS: enable on kernel entry and
disable on exit.

Thx.

-- 
Regards/Gruss,
    Boris.

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