Re: [PATCH 4/4 v4] KVM: VMX: VMXON/VMXOFF usage changes.

[Marcelo Tosatti <mtosatti@redhat.com>]

On Tue, May 11, 2010 at 06:29:48PM +0800, Xu, Dongxiao wrote:
> From: Dongxiao Xu <dongxiao.xu@intel.com>
> 
> SDM suggests VMXON should be called before VMPTRLD, and VMXOFF
> should be called after doing VMCLEAR.
> 
> Therefore in vmm coexistence case, we should firstly call VMXON
> before any VMCS operation, and then call VMXOFF after the
> operation is done.
> 
> Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
> ---
>  arch/x86/kvm/vmx.c |   38 +++++++++++++++++++++++++++++++-------
>  1 files changed, 31 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index c536b9d..dbd47a7 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -168,6 +168,8 @@ static inline struct vcpu_vmx *to_vmx(struct kvm_vcpu *vcpu)
>  
>  static int init_rmode(struct kvm *kvm);
>  static u64 construct_eptp(unsigned long root_hpa);
> +static void kvm_cpu_vmxon(u64 addr);
> +static void kvm_cpu_vmxoff(void);
>  
>  static DEFINE_PER_CPU(struct vmcs *, vmxarea);
>  static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
> @@ -786,8 +788,11 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  	u64 tsc_this, delta, new_offset;
> +	u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
>  
> -	if (vmm_exclusive && vcpu->cpu != cpu)
> +	if (!vmm_exclusive)
> +		kvm_cpu_vmxon(phys_addr);
> +	else if (vcpu->cpu != cpu)
>  		vcpu_clear(vmx);
>  
>  	if (per_cpu(current_vmcs, cpu) != vmx->vmcs) {
> @@ -833,8 +838,10 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  static void vmx_vcpu_put(struct kvm_vcpu *vcpu)
>  {
>  	__vmx_load_host_state(to_vmx(vcpu));
> -	if (!vmm_exclusive)
> +	if (!vmm_exclusive) {
>  		__vcpu_clear(to_vmx(vcpu));
> +		kvm_cpu_vmxoff();
> +	}
>  }
>  
>  static void vmx_fpu_activate(struct kvm_vcpu *vcpu)
> @@ -1257,9 +1264,11 @@ static int hardware_enable(void *garbage)
>  		       FEATURE_CONTROL_LOCKED |
>  		       FEATURE_CONTROL_VMXON_ENABLED);
>  	write_cr4(read_cr4() | X86_CR4_VMXE); /* FIXME: not cpu hotplug safe */
> -	kvm_cpu_vmxon(phys_addr);
>  
> -	ept_sync_global();
> +	if (vmm_exclusive) {
> +		kvm_cpu_vmxon(phys_addr);
> +		ept_sync_global();
> +	}
>  
>  	return 0;

The documentation recommends usage of INVEPT all-context after execution
of VMXON and prior to execution of VMXOFF. Is it not necessary?