[MODERATED] Re: ***UNCHECKED*** [PATCH v7 3/5] NX 3

[Paolo Bonzini <pbonzini@redhat.com>]

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On 25/10/19 10:37, speck for Joerg Roedel wrote:
> I fixed it with this diff:
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index e7970a2e8eae..6e9380a0ca41 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -997,7 +997,7 @@ static bool update_transition_efer(struct vcpu_vmx *vmx, int efer_offset)
>  	 * On CPUs that support "load IA32_EFER", always switch EFER
>  	 * atomically, since it's faster than switching it manually.
>  	 */
> -	if (cpu_has_load_ia32_efer() ||
> +	if ((cpu_has_load_ia32_efer() && (guest_efer & EFER_NX)) ||
>  	    (enable_ept && ((vmx->vcpu.arch.efer ^ host_efer) & EFER_NX))) {
>  		if (!(guest_efer & EFER_LMA))
>  			guest_efer &= ~EFER_LME;
> 

What about this instead (completely untested):

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e7970a2e8eae..1f923dee99e5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -992,6 +992,9 @@ static bool update_transition_efer(struct vcpu_vmx *vmx, int efer_offset)
 		ignore_bits &= ~(u64)EFER_SCE;
 #endif
 
+	guest_efer &= ~ignore_bits;
+	guest_efer |= host_efer & ignore_bits;
+
 	/*
 	 * On EPT, we can't emulate NX, so we must switch EFER atomically.
 	 * On CPUs that support "load IA32_EFER", always switch EFER
@@ -1010,9 +1013,6 @@ static bool update_transition_efer(struct vcpu_vmx *vmx, int efer_offset)
 	} else {
 		clear_atomic_switch_msr(vmx, MSR_EFER);
 
-		guest_efer &= ~ignore_bits;
-		guest_efer |= host_efer & ignore_bits;
-
 		vmx->guest_msrs[efer_offset].data = guest_efer;
 		vmx->guest_msrs[efer_offset].mask = ~ignore_bits;