Different vCPU may have different IWKeys. Hypervisor need do the iwkey
context switch.
This patch introduce a load_iwkey() function to do that. Switches the
host iwkey when the switch_in vCPU satisfies:
1) keylocker feature enabled
2) Different from the current loaded one.
Two opportunities to do the load_iwkey():
1) Guest enables CR4.KL bit.
2) vCPU thread context switch.
load_iwkey() costs ~600 cycles when do the load IWKey action.
Tracked-On: #5695
Signed-off-by: Shuo A Liu <shuo.a.liu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
38cd5b481d