linux-kernel - Re: [PATCH 0/4] random,x86,kvm: Add and use MSR_KVM_GET_RNG

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Date:	Wed, 16 Jul 2014 09:41:11 +0300
From:	Gleb Natapov <gleb@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	kvm@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	Theodore Ts'o <tytso@....edu>, linux-kernel@...r.kernel.org,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	Daniel Borkmann <dborkman@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
Subject: Re: [PATCH 0/4] random,x86,kvm: Add and use MSR_KVM_GET_RNG_SEED

On Tue, Jul 15, 2014 at 07:48:06PM -0700, Andy Lutomirski wrote:
> virtio-rng is both too complicated and insufficient for initial rng
> seeding.  It's far too complicated to use for KASLR or any other
> early boot random number needs.  It also provides /dev/random-style
> bits, which means that making guest boot wait for virtio-rng is
> unacceptably slow, and doing it asynchronously means that
> /dev/urandom might be predictable when userspace starts.
> 
> This introduces a very simple synchronous mechanism to get
> /dev/urandom-style bits.
Why can't you use RDRAND instruction for that?

> 
> This is a KVM change: am I supposed to write a unit test somewhere?
> 
> Andy Lutomirski (4):
>   x86,kvm: Add MSR_KVM_GET_RNG_SEED and a matching feature bit
>   random,x86: Add arch_get_slow_rng_u64
>   random: Seed pools from arch_get_slow_rng_u64 at startup
>   x86,kaslr: Use MSR_KVM_GET_RNG_SEED for KASLR if available
> 
>  Documentation/virtual/kvm/cpuid.txt  |  3 +++
>  arch/x86/Kconfig                     |  4 ++++
>  arch/x86/boot/compressed/aslr.c      | 27 +++++++++++++++++++++++++++
>  arch/x86/include/asm/archslowrng.h   | 30 ++++++++++++++++++++++++++++++
>  arch/x86/include/uapi/asm/kvm_para.h |  2 ++
>  arch/x86/kernel/kvm.c                | 22 ++++++++++++++++++++++
>  arch/x86/kvm/cpuid.c                 |  3 ++-
>  arch/x86/kvm/x86.c                   |  4 ++++
>  drivers/char/random.c                | 14 +++++++++++++-
>  include/linux/random.h               |  9 +++++++++
>  10 files changed, 116 insertions(+), 2 deletions(-)
>  create mode 100644 arch/x86/include/asm/archslowrng.h
> 
> -- 
> 1.9.3
> 
> --
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--
			Gleb.
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