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

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Message-ID: <53C6A362.7090709@redhat.com>
Date:	Wed, 16 Jul 2014 18:08:02 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>
CC:	Daniel Borkmann <dborkman@...hat.com>,
	Gleb Natapov <gleb@...nel.org>, kvm list <kvm@...r.kernel.org>,
	"Theodore Ts'o" <tytso@....edu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>, X86 ML <x86@...nel.org>,
	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

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.

Paolo
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