x86/vvmx: check vmcs address in vmread/vmwrite

x86/vvmx: check vmcs address in vmread/vmwrite

If nested vmcs's address is invalid, virtual_vmcs_enter() will fail
during vmread/vmwrite:

(XEN) Xen BUG at .../git/upstream/xen/xen/include/asm/hvm/vmx/vmx.h:333
(XEN) ----[ Xen-4.9-unstable  x86_64  debug=y   Tainted:    H ]----
(XEN) Xen call trace:
(XEN)    [<ffff82d0801f925e>] vmcs.c#arch/x86/hvm/vmx/vmcs.o.unlikely+0x28/0x19a
(XEN)    [<ffff82d0801f60e3>] virtual_vmcs_vmwrite_safe+0x16/0x52
(XEN)    [<ffff82d080202cb2>] nvmx_handle_vmwrite+0x70/0xfe
(XEN)    [<ffff82d0801fe98a>] vmx_vmexit_handler+0x1379/0x1c49
(XEN)    [<ffff82d08020427c>] vmx_asm_vmexit_handler+0x3c/0x120

Fix this by emulating VMfailInvalid if the address is invalid.

Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>