linux-kernel - Re: [PATCH v3 0/4] Distinguish between variants of IBPB

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <875xrog5kv.ffs@tglx>
Date: Sun, 25 Aug 2024 14:17:04 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Jim Mattson <jmattson@...gle.com>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>, Pawan Gupta
 <pawan.kumar.gupta@...ux.intel.com>, Josh Poimboeuf <jpoimboe@...nel.org>,
 Jim Mattson <jmattson@...gle.com>, Sandipan Das <sandipan.das@....com>,
 Kai Huang <kai.huang@...el.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v3 0/4] Distinguish between variants of IBPB

On Fri, Aug 23 2024 at 11:53, Jim Mattson wrote:

> Prior to Zen4, AMD's IBPB did not flush the RAS (or, in Intel
> terminology, the RSB). Hence, the older version of AMD's IBPB was not
> equivalent to Intel's IBPB. However, KVM has been treating them as
> equivalent, synthesizing Intel's CPUID.(EAX=7,ECX=0):EDX[bit 26] on any
> platform that supports the synthetic features X86_FEATURE_IBPB and
> X86_FEATURE_IBRS.
>
> Equivalence also requires a previously ignored feature on the AMD side,
> CPUID Fn8000_0008_EBX[IBPB_RET], which is enumerated on Zen4.
>
> v3: Pass through IBPB_RET from hardware to userspace. [Tom]
>     Derive AMD_IBPB from X86_FEATURE_SPEC_CTRL rather than
>     X86_FEATURE_IBPB. [Tom]
>     Clarify semantics of X86_FEATURE_IBPB.
>
> v2: Use IBPB_RET to identify semantic equality. [Venkatesh]

Assuming this goes through the KVM tree:

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>