From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@amacapital.net>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: Daniel Borkmann <dborkman@redhat.com>,
Gleb Natapov <gleb@kernel.org>, kvm list <kvm@vger.kernel.org>,
"Theodore Ts'o" <tytso@mit.edu>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Kees Cook <keescook@chromium.org>, X86 ML <x86@kernel.org>,
Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Subject: Re: [PATCH 0/4] random,x86,kvm: Add and use MSR_KVM_GET_RNG_SEED
Date: Wed, 16 Jul 2014 09:03:02 -0700 [thread overview]
Message-ID: <53C6A236.7040904@zytor.com> (raw)
In-Reply-To: <CALCETrVLJ7qH3y04K9Sz1pU3i9+H9Cq_RoDfBeWnsH0VC68qKw@mail.gmail.com>
On 07/16/2014 07:07 AM, Andy Lutomirski wrote:
>
> This patch has nothing whatsoever to do with how much I trust the CPU
> vs the hypervisor. It's for the enormous installed base of machines
> without RDRAND.
>
> hpa suggested emulating RDRAND awhile ago, but I think that'll
> unusably slow -- the kernel uses RDRAND in various places where it's
> expected to be fast, and not using it at all will be preferable to
> causing a VM exit for every few bytes. I've been careful to only use
> this in the guest in places where a few hundred to a few thousand
> cycles per 64 bits of RNG seed is acceptable.
>
I suggested emulating RDRAND *but not set the CPUID bit*. We already
developed a protocol in KVM/Qemu to enumerate emulated features (created
for MOVBE as I recall), specifically to service the semantic "feature X
will work but will be substantially slower than normal."
-hpa
next prev parent reply other threads:[~2014-07-16 16:03 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-16 2:48 [PATCH 0/4] random,x86,kvm: Add and use MSR_KVM_GET_RNG_SEED Andy Lutomirski
2014-07-16 2:48 ` [PATCH 1/4] x86,kvm: Add MSR_KVM_GET_RNG_SEED and a matching feature bit Andy Lutomirski
2014-07-16 2:48 ` [PATCH 2/4] random,x86: Add arch_get_slow_rng_u64 Andy Lutomirski
2014-07-16 2:48 ` [PATCH 3/4] random: Seed pools from arch_get_slow_rng_u64 at startup Andy Lutomirski
2014-07-16 2:48 ` [PATCH 4/4] x86,kaslr: Use MSR_KVM_GET_RNG_SEED for KASLR if available Andy Lutomirski
2014-07-16 6:41 ` [PATCH 0/4] random,x86,kvm: Add and use MSR_KVM_GET_RNG_SEED Gleb Natapov
2014-07-16 7:10 ` Daniel Borkmann
2014-07-16 7:23 ` Gleb Natapov
2014-07-16 7:36 ` Paolo Bonzini
2014-07-16 14:07 ` Andy Lutomirski
2014-07-16 14:32 ` Paolo Bonzini
2014-07-16 14:53 ` Gleb Natapov
2014-07-16 15:56 ` Andy Lutomirski
2014-07-16 16:03 ` H. Peter Anvin [this message]
2014-07-16 16:08 ` Paolo Bonzini
2014-07-16 16:13 ` H. Peter Anvin
2014-07-16 16:21 ` Gleb Natapov
2014-07-16 20:20 ` H. Peter Anvin
2014-07-16 21:32 ` Andy Lutomirski
2014-07-16 21:36 ` H. Peter Anvin
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