Howdy,

Attached patch implements lazy-fpu save/restore for VT.  VMEXIT time 
improves by about 10% (~550 cycles).  I had to do a couple more things 
to get it working than I had to do with SVM.  I changed the CR0 host 
mask to be all 1's so that any attempt to write to CR0 causes a VMEXIT.  
I don't think there are any remaining bits now that we want to trap TS 
that are safe for the guest to access and are in the fast-paths.

Since we're trapping TS, I had to implement CLTS exit handling.  
vcpu->cr0 also had a rather bizarre life cycle.  After a set_cr0, it was 
a proper shadow of the guest's CR0.  However, after a decache_cr0, it 
would contain the host's version of the bits covered by the CR0 host 
mask so it was no longer a proper shadow.

I got rid of the CR0 caching and made vcpu->cr0 always be equivalent to 
CR0_READ_SHADOW.  Once these changes were made, the rest of the patch 
was much like the SVM one.

Regards,

Anthony Liguori