linux-kernel - Re: [PATCH 0/2] Remove some hardcoded SEV-SNP guest policy checks during guest launch

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 for Android: free password hash cracker in your pocket

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

Message-ID: <175079224437.515260.14294578957654984603.b4-ty@google.com>
Date: Tue, 24 Jun 2025 12:38:45 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	x86@...nel.org, Tom Lendacky <thomas.lendacky@....com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Ingo Molnar <mingo@...hat.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Michael Roth <michael.roth@....com>
Subject: Re: [PATCH 0/2] Remove some hardcoded SEV-SNP guest policy checks
 during guest launch

On Thu, 29 May 2025 16:17:58 -0500, Tom Lendacky wrote:
> This series removes some guest policy checks that can be better controlled
> by the SEV firmware.
> 
> - Remove the check for the SMT policy bit. Currently, a check is made to
>   ensure the SMT policy bit is set to 1. However, there is no reason for
>   KVM to do this. The SMT policy bit, when 0, is used to ensure that SMT
>   has been disabled *in the BIOS.* As this does not require any special
>   support within KVM, the check can be safely removed to allow the SEV
>   firmware to determine whether the system meets the policy.
> 
> [...]

Applied to kvm-x86 svm.  FWIW, I'm not entirely sure I love the idea of doing
nothing, e.g. it'd be nice to enumerate support to userspace.  But adding a
bunch of code to regurgitate information that's likely available to userspace
(or more likely, the platform admin/orchestrator) doesn't seem worthwile either.

I'll make sure to flag this for Paolo's eyeballs.

[1/2] KVM: SVM: Allow SNP guest policy disallow running with SMT enabled
      https://github.com/kvm-x86/linux/commit/9f4701e05fae
[2/2] KVM: SVM: Allow SNP guest policy to specify SINGLE_SOCKET
      https://github.com/kvm-x86/linux/commit/24be2b7956a5

--
https://github.com/kvm-x86/kvm-unit-tests/tree/next