Re: [PATCH] KVM: nVMX: Reset vmxon_ptr upon VMXOFF emulation.

[Sean Christopherson <seanjc@google.com>]

On Thu, Sep 09, 2021, Yu Zhang wrote:
> From: Vitaly Kuznetsov <vkuznets@redhat.com>
> 
> Currently, 'vmx->nested.vmxon_ptr' is not reset upon VMXOFF
> emulation. This is not a problem per se as we never access
> it when !vmx->nested.vmxon. But this should be done to avoid
> any issue in the future.
> 
> Also, initialize the vmxon_ptr when vcpu is created.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
> ---
>  arch/x86/kvm/vmx/nested.c | 1 +
>  arch/x86/kvm/vmx/vmx.c    | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 90f34f12f883..e4260f67caac 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -289,6 +289,7 @@ static void free_nested(struct kvm_vcpu *vcpu)
>  	kvm_clear_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
>  
>  	vmx->nested.vmxon = false;
> +	vmx->nested.vmxon_ptr = -1ull;

Looks like the "-1ull" comes from current_vmptr and friends, but using INVALID_GPA
is more appropriate.  It's the same value, but less arbitrary.  The other usage of
-1ull for guest physical addresses should really be cleaned up, too.