From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 0/4] random,x86,kvm: Add and use MSR_KVM_GET_RNG_SEED
Date: Wed, 16 Jul 2014 18:08:02 +0200
Message-ID: <53C6A362.7090709@redhat.com>
References: <cover.1405477965.git.luto@amacapital.net> <20140716064110.GV18167@minantech.com> <53C62563.6050106@redhat.com> <53C62B68.50702@redhat.com> <CALCETrVLJ7qH3y04K9Sz1pU3i9+H9Cq_RoDfBeWnsH0VC68qKw@mail.gmail.com> <53C6A236.7040904@zytor.com>
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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>
To: "H. Peter Anvin" <hpa@zytor.com>,
	Andy Lutomirski <luto@amacapital.net>
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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