Received-SPF: pass (google.com: domain of linux-kernel+bounces-45101-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Precedence: bulk
MIME-Version: 1.0
References: <20240130083007.1876787-1-kirill.shutemov@linux.intel.com>
 <20240130083007.1876787-2-kirill.shutemov@linux.intel.com>
 <CAHmME9qsfOdOEHHw_MOBmt6YAtncbbqP9LPK2dRjuOp1CrHzRA@mail.gmail.com>
 <DM8PR11MB57507611D651E6D7CBC2A2F3E77D2@DM8PR11MB5750.namprd11.prod.outlook.com>
 <88a72370-e300-4bbc-8077-acd1cc831fe7@intel.com> <CAHmME9oSQbd3V8+qR0e9oPb7ppO=E7GrCW-a2RN8QNdY_ARbSQ@mail.gmail.com>
 <a076974c-e2c7-43c9-9858-71c913361cea@intel.com> <81359B1E-5293-4919-B319-59483C1EA12E@zytor.com>
In-Reply-To: <81359B1E-5293-4919-B319-59483C1EA12E@zytor.com>
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Tue, 30 Jan 2024 19:23:23 +0100
Message-ID: <CAHmME9p60_N2zkx48fW-DQPAoXEOcFBe7pHAXQtF8rA3aqY-xQ@mail.gmail.com>
Subject: Re: [PATCH 2/2] x86/random: Issue a warning if RDRAND or RDSEED fails
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@intel.com>, "Reshetova, Elena" <elena.reshetova@intel.com>, 
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Thomas Gleixner <tglx@linutronix.de>, 
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, 
	Dave Hansen <dave.hansen@linux.intel.com>, "x86@kernel.org" <x86@kernel.org>, 
	"Theodore Ts'o" <tytso@mit.edu>, 
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>, 
	"Nakajima, Jun" <jun.nakajima@intel.com>, Tom Lendacky <thomas.lendacky@amd.com>, 
	"Kalra, Ashish" <ashish.kalra@amd.com>, Sean Christopherson <seanjc@google.com>, 
	"linux-coco@lists.linux.dev" <linux-coco@lists.linux.dev>, 
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Tue, Jan 30, 2024 at 7:16=E2=80=AFPM H. Peter Anvin <hpa@zytor.com> wrot=
e:
>
> On January 30, 2024 9:58:09 AM PST, Dave Hansen <dave.hansen@intel.com> w=
rote:
> >On 1/30/24 09:49, Jason A. Donenfeld wrote:
> >>> Anybody disagree?
> >> Yes, I disagree. I made a trivial test that shows RDSEED breaks easily
> >> in a busy loop. So at the very least, your statement holds true only
> >> for RDRAND.
> >
> >Well, darn. :)
> >
> >Any chance you could share some more information about the environment
> >where you're seeing this?  It'd be good to reconcile what you're seeing
> >with how the hardware is expected to behave.
>
> What CPU is this and could you clarify exactly how you run your busy loop=
?

That is already in this thread already. Maybe catch up on the whole
thing and then jump back in?
https://lore.kernel.org/all/Zbjw5hRHr_E6k18r@zx2c4.com/