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

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Message-ID: <276aaeee-cb01-47d3-a3bf-f8fa2e59016c@intel.com>
Date: Mon, 29 Jan 2024 08:30:11 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: "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,
 Theodore Ts'o <tytso@....edu>, "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
 Elena Reshetova <elena.reshetova@...el.com>,
 Jun Nakajima <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-kernel@...r.kernel.org
Subject: Re: [RFC] Randomness on confidential computing platforms

On 1/26/24 05:42, Kirill A. Shutemov wrote:
> 3. Panic after enough re-tries of RDRAND/RDSEED instructions fail.
>    Another DoS variant against the Guest.

I think Sean was going down the same path, but I really dislike the idea
of having TDX-specific (or CoCo-specific) policy here.

How about we WARN_ON() RDRAND/RDSEED going bonkers?  The paranoid folks
can turn on panic_on_warn, if they haven't already.