linux-kernel - Re: [PATCH v6 06/20] KVM: VMX: Set FRED MSR intercepts

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] [day] [month] [year] [list]

Message-ID: <2f84aed4-8da2-4ac0-8714-3fb1aca51515@citrix.com>
Date: Tue, 26 Aug 2025 23:20:27 +0100
From: Andrew Cooper <andrew.cooper3@...rix.com>
To: Xin Li <xin@...or.com>, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org, linux-doc@...r.kernel.org
Cc: pbonzini@...hat.com, seanjc@...gle.com, corbet@....net,
 tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, luto@...nel.org,
 peterz@...radead.org, chao.gao@...el.com, hch@...radead.org
Subject: Re: [PATCH v6 06/20] KVM: VMX: Set FRED MSR intercepts

On 26/08/2025 11:03 pm, Xin Li wrote:
> On 8/26/2025 11:50 AM, Andrew Cooper wrote:
>> This distinction only matters for guests, and adding the CET-SS
>> precondition makes things simpler overall for both VMMs and guests.  So
>> can't this just be fixed up before being integrated into the SDM?
>
> +1 :)

I've just realised why these MSRs are tied together in this way.

As written, the VMX Entry/Exit Load/Save FRED controls do not allow for
a logical configuration of FRED && !CET-SS.  Both sets of stack pointers
are treated the same.

This is horrible.  I'm less certain if this can simply be fixed by
changing the SDM.

~Andrew