Re: [PATCH 5/5] KVM: VMX: Atomically switch efer if EPT && !EFER.NX

[Marcelo Tosatti <mtosatti@redhat.com>]

Avi,

This patch breaks WinVista.64 install.

On Wed, Apr 28, 2010 at 04:47:19PM +0300, Avi Kivity wrote:
> When EPT is enabled, we cannot emulate EFER.NX=0 through the shadow page
> tables.  This causes accesses through ptes with bit 63 set to succeed instead
> of failing a reserved bit check.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  arch/x86/kvm/vmx.c |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index ae22dcf..cc78fee 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -678,6 +678,17 @@ static bool update_transition_efer(struct vcpu_vmx *vmx, int efer_offset)
>  	guest_efer |= host_efer & ignore_bits;
>  	vmx->guest_msrs[efer_offset].data = guest_efer;
>  	vmx->guest_msrs[efer_offset].mask = ~ignore_bits;
> +
> +	clear_atomic_switch_msr(vmx, MSR_EFER);
> +	/* On ept, can't emulate nx, and must switch nx atomically */
> +	if (enable_ept && ((vmx->vcpu.arch.efer ^ host_efer) & EFER_NX)) {
> +		guest_efer = vmx->vcpu.arch.efer;
> +		if (!(guest_efer & EFER_LMA))
> +			guest_efer &= ~EFER_LME;
> +		add_atomic_switch_msr(vmx, MSR_EFER, guest_efer, host_efer);
> +		return false;
> +	}
> +
>  	return true;
>  }
>  
> -- 
> 1.7.0.4