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From: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>
To: Pavel Machek <pavel@ucw.cz>, "tytso@mit.edu" <tytso@mit.edu>,
	"nhorman@tuxdriver.com" <nhorman@tuxdriver.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Chen Yu <yu.c.chen@intel.com>, Jonathan Corbet <corbet@lwn.net>
Subject: Re: Non-random RDRAND Re: [PATCH] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h
Date: Thu, 15 Aug 2019 13:01:16 +0000	[thread overview]
Message-ID: <0ea34954-10d4-03f9-fce6-d25aa574bb43@amd.com> (raw)
In-Reply-To: <20190814232434.GA31769@amd>

On 8/14/19 6:24 PM, Pavel Machek wrote:
> On Wed 2019-08-14 21:17:41, Lendacky, Thomas wrote:
>> From: Tom Lendacky <thomas.lendacky@amd.com>
>>
>> There have been reports of RDRAND issues after resuming from suspend on
>> some AMD family 15h and family 16h systems. This issue stems from BIOS
>> not performing the proper steps during resume to ensure RDRAND continues
>> to function properly.
> 
> Burn it with fire!
> 
> I mean... people were afraid RDRAND would be backdoored, and you now
> confirm ... it indeed _is_ backdoored? /., here's news for you!
> 
> So what is the impact? Does it give random-looking but predictable
> numbers after resume? Does it give all zeros? Something else?

See this article:
https://www.phoronix.com/scan.php?page=news_item&px=AMD-CPUs-RdRand-Suspend

Thanks,
Tom

> 
>>  
>> +	rdrand_force	[X86]
>> +			On certain AMD processors, the advertisement of the
>> +			RDRAND instruction has been disabled by the kernel
>> +			because of buggy BIOS support, specifically around the
>> +			suspend/resume path. This option allows for overriding
>> +			that decision if it is known that the BIOS support for
>> +			RDRAND is not buggy on the system.
> 
> But this is not how we normally deal with buggy BIOSes. We don't want
> user to have to decide this...
> 
> Should we introduce black-list or white-list of BIOS versions?
> 
> Hmm. Actually.
> 
> You are the CPU vendor. Surely you can tell us how to init RDRAND in
> kernel if BIOS failed to do that... can you?
> 
> 									Pavel
> 

  parent reply	other threads:[~2019-08-15 13:01 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14 21:17 [PATCH] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h Lendacky, Thomas
2019-08-14 23:24 ` Non-random RDRAND " Pavel Machek
2019-08-14 23:38   ` Pavel Machek
2019-08-15 13:01   ` Lendacky, Thomas [this message]
2019-08-15 15:12   ` Theodore Y. Ts'o
2019-08-16  9:07     ` Pavel Machek
2019-08-16 14:42     ` Neil Horman
2019-08-15  7:21 ` Borislav Petkov
2019-08-15 13:47   ` Lendacky, Thomas
2019-08-15 15:34     ` Borislav Petkov
2019-08-15 20:14       ` Thomas Gleixner
2019-08-15 20:59 ` Andrew Cooper
2019-08-15 21:04   ` Thomas Gleixner
2019-08-15 21:05   ` Borislav Petkov
2019-08-15 21:25     ` Andrew Cooper
2019-08-17  8:44       ` Borislav Petkov
2019-08-17 11:43         ` Andrew Cooper
2019-08-18 16:32           ` Thomas Gleixner
2019-08-16 15:19 ` Andy Lutomirski

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