Re: [PATCH v1 2/2] KVM: VMX: always require WB memory type for EPT

[Paolo Bonzini <pbonzini@redhat.com>]

On 10/08/2017 15:35, David Hildenbrand wrote:
> We already always set that type but don't check if it is supported. Also
> for nVMX, we only support WB for now. Let's just require it.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>

It may only happen on a broken nested hypervisor, so the patch is okay.

Paolo

> ---
>  arch/x86/kvm/vmx.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index f6638ed..023c6dc 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1200,6 +1200,11 @@ static inline bool cpu_has_vmx_ept_4levels(void)
>  	return vmx_capability.ept & VMX_EPT_PAGE_WALK_4_BIT;
>  }
>  
> +static inline bool cpu_has_vmx_ept_mt_wb(void)
> +{
> +	return vmx_capability.ept & VMX_EPTP_WB_BIT;
> +}
> +
>  static inline bool cpu_has_vmx_ept_ad_bits(void)
>  {
>  	return vmx_capability.ept & VMX_EPT_AD_BIT;
> @@ -4302,7 +4307,6 @@ static u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa)
>  {
>  	u64 eptp = VMX_EPTP_MT_WB | VMX_EPTP_PWL_4;
>  
> -	/* TODO write the value reading from MSR */
>  	if (enable_ept_ad_bits &&
>  	    (!is_guest_mode(vcpu) || nested_ept_ad_enabled(vcpu)))
>  		eptp |= VMX_EPTP_AD_ENABLE_BIT;
> @@ -6638,7 +6642,8 @@ static __init int hardware_setup(void)
>  		init_vmcs_shadow_fields();
>  
>  	if (!cpu_has_vmx_ept() ||
> -	    !cpu_has_vmx_ept_4levels()) {
> +	    !cpu_has_vmx_ept_4levels() ||
> +	    !cpu_has_vmx_ept_mt_wb()) {
>  		enable_ept = 0;
>  		enable_unrestricted_guest = 0;
>  		enable_ept_ad_bits = 0;
>