Re: [PATCH 0/4] random,x86,kvm: Add and use MSR_KVM_GET_RNG_SEED

Gleb Natapov
2014-07-16T06:41:16Z

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.