linux-kernel - Re: [PATCH 03/16] x86/tsc: Add helper to register CPU and TSC freq calibration routines

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: <20250211203250.GHZ6uz8qs-bzcbi0_b@fat_crate.local>
Date: Tue, 11 Feb 2025 21:32:50 +0100
From: Borislav Petkov <bp@...en8.de>
To: Sean Christopherson <seanjc@...gle.com>,
	Tom Lendacky <thomas.lendacky@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Juergen Gross <jgross@...e.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	Ajay Kaher <ajay.kaher@...adcom.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org,
	linux-coco@...ts.linux.dev, virtualization@...ts.linux.dev,
	linux-hyperv@...r.kernel.org, kvm@...r.kernel.org,
	xen-devel@...ts.xenproject.org, Nikunj A Dadhania <nikunj@....com>
Subject: Re: [PATCH 03/16] x86/tsc: Add helper to register CPU and TSC freq
 calibration routines

On Tue, Feb 11, 2025 at 09:43:23AM -0800, Sean Christopherson wrote:
> It conflates two very different things: host/bare metal support for memory
> encryption, and SEV guest support.  For kernels that will never run in a VM,
> pulling in all the SEV guest code just to enable host-side support for SME (and
> SEV) is very undesirable.

Well, that might've grown in the meantime... when we started it, it was all
small so it didn't really matter and we kept it simple. That's why I never
thought about it. And actually, we've been thinking of even ripping out SME
in favor of TSME which is transparent and doesn't need any SME glue. But there
was some reason why we didn't want to do it yet, Tom would know.

As to carving it out now, meh, dunno how much savings that would be. Got
a student to put on that task? :-P

> And in this case, because AMD_MEM_ENCRYPT gates both host and guest code, it
> can't depend on HYPERVISOR_GUEST like it should, because taking a dependency on
> HYPERVISOR_GUEST to enable SME is obviously wrong.

Right.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette