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From: Christopher Covington <cov@codeaurora.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Theodore Ts'o <tytso@mit.edu>, kvm list <kvm@vger.kernel.org>,
	Gleb Natapov <gleb@kernel.org>,
	Linux Virtualization <virtualization@lists.linux-foundation.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Nadav Amit <nadav.amit@gmail.com>
Subject: Re: Standardizing an MSR or other hypercall to get an RNG seed?
Date: Mon, 22 Sep 2014 09:31:55 -0400	[thread overview]
Message-ID: <542024CB.2070704@codeaurora.org> (raw)
In-Reply-To: <541CA440.8080909@zytor.com>

On 09/19/2014 05:46 PM, H. Peter Anvin wrote:
> On 09/19/2014 01:46 PM, Andy Lutomirski wrote:
>>>
>>> However, it sounds to me that at least for KVM, it is very easy just to emulate the RDRAND instruction. The hypervisor would report to the guest that RDRAND is supported in CPUID and the emulate the instruction when guest executes it. KVM already traps guest #UD (which would occur if RDRAND executed while it is not supported) - so this scheme wouldn’t introduce additional overhead over RDMSR.
>>
>> Because then guest user code will think that rdrand is there and will
>> try to use it, resulting in abysmal performance.
>>
> 
> Yes, the presence of RDRAND implies a cheap and inexhaustible entropy
> source.

A guest kernel couldn't make it look like RDRAND is not present to guest
userspace?

Christopher

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
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  reply	other threads:[~2014-09-22 13:31 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-18  2:50 Standardizing an MSR or other hypercall to get an RNG seed? Andy Lutomirski
2014-09-18 14:40 ` KY Srinivasan
     [not found] ` <2aa00301e9af4826b5781e01709f81e7@BY2PR0301MB0711.namprd03.prod.outlook.com>
2014-09-18 14:43   ` H. Peter Anvin
2014-09-18 15:38     ` Andy Lutomirski
2014-09-18 15:44       ` Andy Lutomirski
2014-09-18 15:58         ` Paolo Bonzini
2014-09-18 16:36       ` KY Srinivasan
     [not found]       ` <5b9c7dcde3824e49a25f3ee00844b868@BY2PR0301MB0711.namprd03.prod.outlook.com>
2014-09-18 17:13         ` Nakajima, Jun
2014-09-18 17:17           ` Paolo Bonzini
     [not found]           ` <541B13B8.1020006@redhat.com>
2014-09-18 17:20             ` Jake Oshins
2014-09-18 17:20             ` KY Srinivasan
     [not found]             ` <b697ef83ae594d8fb34347339dd52dfa@BY2PR0301MB0711.namprd03.prod.outlook.com>
2014-09-18 17:42               ` Nakajima, Jun
2014-09-18 18:35                 ` Andy Lutomirski
2014-09-18 18:39                   ` H. Peter Anvin
2014-09-18 18:54                     ` Niels Ferguson
2014-09-18 19:03                       ` Andy Lutomirski
2014-09-18 21:54                         ` David Hepkin
     [not found]                         ` <572ba53a2e1e4278823f718a421e2c1d@BY2PR03MB585.namprd03.prod.outlook.com>
2014-09-19  6:04                           ` Paolo Bonzini
2014-09-18 18:58                   ` Paolo Bonzini
2014-09-18 19:07                     ` Andy Lutomirski
2014-09-18 21:21                       ` Nakajima, Jun
2014-09-18 21:35                         ` Andy Lutomirski
2014-09-18 21:46                       ` David Hepkin
     [not found]                       ` <0180a8dfcad746a895755c4374853c16@BY2PR03MB585.namprd03.prod.outlook.com>
2014-09-18 21:57                         ` H. Peter Anvin
2014-09-18 22:07                           ` Andy Lutomirski
2014-09-19  0:49                             ` Nakajima, Jun
     [not found]                             ` <CAL54oT1Q8kABge=t4s5REVWWakboON-6vfszMRkVz=ks_3vRoA@mail.gmail.com>
2014-09-19  1:03                               ` Andy Lutomirski
2014-09-19  1:28                                 ` Andy Lutomirski
     [not found]                                 ` <CALCETrWZ1cF23aT82yGfTKS48d2G+_Od7hEkAzDWzDhqpHNVqA@mail.gmail.com>
2014-09-19 16:14                                   ` Nakajima, Jun
2014-09-19 16:22                                     ` Paolo Bonzini
2014-09-19 16:40                                     ` H. Peter Anvin
2014-09-19 17:21                                       ` Andy Lutomirski
2014-09-19 17:36                                         ` H. Peter Anvin
2014-09-19 17:39                                           ` Andy Lutomirski
2014-09-19 22:05                                       ` Theodore Ts'o
2014-09-19 22:06                                         ` Andy Lutomirski
2014-09-19 22:57                                           ` Nakajima, Jun
2014-09-19 22:57                                           ` Theodore Ts'o
2014-09-19 23:12                                             ` Andy Lutomirski
2014-09-19 23:29                                               ` H. Peter Anvin
2014-09-19 23:35                                                 ` Theodore Ts'o
2014-09-19 23:41                                                   ` Andy Lutomirski
2014-09-20  0:06                                                   ` H. Peter Anvin
2014-09-19 23:29                                               ` H. Peter Anvin
2014-09-18 22:00                         ` Andy Lutomirski
2014-09-18 22:03                           ` H. Peter Anvin
2014-09-19 16:37                           ` Gleb Natapov
2014-09-19 16:40                             ` H. Peter Anvin
2014-09-19 16:53                               ` Gleb Natapov
2014-09-19 17:08                                 ` H. Peter Anvin
2014-09-19 17:15                                   ` Gleb Natapov
2014-09-19 17:18                                     ` H. Peter Anvin
2014-09-19 17:49                                       ` Gleb Natapov
2014-09-19 18:02                                         ` Andy Lutomirski
2014-09-19 18:12                                           ` Gleb Natapov
2014-09-19 18:20                                             ` Andy Lutomirski
2014-09-19 20:53                                               ` Gleb Natapov
2014-09-22  4:11                                               ` Alok Kataria
2014-09-19 17:18                                     ` H. Peter Anvin
2014-09-19 17:21                                 ` Andy Lutomirski
2014-09-19 17:59                                   ` Gleb Natapov
2014-09-18 18:56                 ` Paolo Bonzini
2014-09-19 18:30 ` Christopher Covington
2014-09-19 18:42   ` Andy Lutomirski
2014-09-19 20:21     ` Nadav Amit
     [not found]     ` <15C8041A-3488-4693-B329-3A9FE77A0CB9@gmail.com>
2014-09-19 20:46       ` Andy Lutomirski
2014-09-19 21:46         ` H. Peter Anvin
2014-09-22 13:31           ` Christopher Covington [this message]
2014-09-22 14:17             ` H. Peter Anvin
2014-09-22 14:18               ` H. Peter Anvin
2014-09-22 23:01             ` H. Peter Anvin
2014-09-21 12:39         ` Paolo Bonzini
2014-09-22 13:33     ` Christopher Covington

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