nested vmx: fix CR0/CR4 emulation

nested vmx: fix CR0/CR4 emulation

While emulate CR0 and CR4 for nested virtualization, set the CR0/CR4
guest host mask to 0xffffffff in shadow VMCS, then calculate the
corresponding read shadow separately for CR0 and CR4. While getting
the VM exit for CR0/CR4 access, check if L1 VMM owns the bit. If so,
inject the VM exit to L1 VMM. Otherwise, L0 will handle it and sync
the value to L1 virtual VMCS.

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
Committed-by: Jan Beulich <jbeulich@suse.com>