From: "H. Peter Anvin" <hpa@zytor.com>
To: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Andy Lutomirski <luto@amacapital.net>,
Daniel Borkmann <dborkman@redhat.com>,
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 13:20:53 -0700 [thread overview]
Message-ID: <53C6DEA5.7010203@zytor.com> (raw)
In-Reply-To: <20140716162133.GO4399@minantech.com>
On 07/16/2014 09:21 AM, Gleb Natapov wrote:
> On Wed, Jul 16, 2014 at 09:13:23AM -0700, H. Peter Anvin wrote:
>> On 07/16/2014 09:08 AM, Paolo Bonzini wrote:
>>> Il 16/07/2014 18:03, H. Peter Anvin ha scritto:
>>>> 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."
>>>
>>> But those will set the CPUID bit. There is currently no way for KVM
>>> guests to know if a CPUID bit is real or emulated.
>>>
>>
>> OK, so there wasn't any protocol implemented in the end. I sit corrected.
>>
> That protocol that was implemented is between qemu and kvm, not kvm and a guest.
>
Either which way, the notion was to have a PV CPUID bit like the
proposed kvm_get_rng_seed bit, but to have it exercised by executing RDRAND.
The biggest reason to *not* do this would be that with an MSR it is not
available to guest user space, which may be better under the circumstances.
-hpa
next prev parent reply other threads:[~2014-07-16 20:21 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
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 [this message]
2014-07-16 21:32 ` Andy Lutomirski
2014-07-16 21:36 ` H. Peter Anvin
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