linux-kernel - Re: [RFC] Randomness on confidential computing platforms

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Message-ID: <4f717166-863e-4145-8b8b-37e09415e855@suse.com>
Date: Fri, 26 Jan 2024 18:35:59 +0200
From: Nikolay Borisov <nik.borisov@...e.com>
To: Daniel P. Berrangé <berrange@...hat.com>,
 "Reshetova, Elena" <elena.reshetova@...el.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
 Theodore Ts'o <tytso@....edu>, "Jason A. Donenfeld" <Jason@...c4.com>,
 Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
 "Nakajima, Jun" <jun.nakajima@...el.com>,
 Tom Lendacky <thomas.lendacky@....com>, "Kalra, Ashish"
 <ashish.kalra@....com>, Sean Christopherson <seanjc@...gle.com>,
 "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] Randomness on confidential computing platforms

On 26.01.24 г. 17:57 ч., Daniel P. Berrangé wrote:
> If the CPU performance counters could report RDRAND exhaustion directly,
> then the host admin could trust that information and monitor it, but the
> host shouldn't rely on the (hostile) guest software to tell it about

I guess it really depends on the POV - from the POV of an encrypted 
guest the VMM is hostile so we ideally don't like to divulge more 
information than is absolutely necessary.

OTOH, from the POV of the VMM we could say that the guest could be 
running anything and so a facility like that could cause some confusion 
on the VMM site.

I think it would be very hard to reconcile the 2 views.

> exhaustion.