linux-kernel - Re: [PATCH 1/2] KVM: MMU: fix ept=0/pte.u=0/pte.w=0/CR0.WP=0/CR4.SMEP=1/EFER.NX=0 combo

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Date:	Thu, 10 Mar 2016 11:01:26 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:	stable@...r.kernel.org, Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH 1/2] KVM: MMU: fix
 ept=0/pte.u=0/pte.w=0/CR0.WP=0/CR4.SMEP=1/EFER.NX=0 combo



On 10/03/2016 09:27, Xiao Guangrong wrote:
> So it only hurts the box which has cpu_has_load_ia32_efer support otherwise
> NX is inherited from kernel (kernel always sets NX if CPU supports it),
> right?

Yes, but I think !cpu_has_load_ia32_efer && SMEP does not exist.  On the
other hand it's really only when disabling ept, so it's a weird corner
case that only happens during testing.

Paolo