My understanding is that BOOTMGR goes to WINLOAD when booting Vista or later. The routine that ensures the correct CR4/XCR0 values in this case is called bootmg

My understanding is that BOOTMGR goes to WINLOAD when booting Vista or later. The routine that ensures the correct CR4/XCR0 values in this case is called bootmgr!ArchRestoreProcessorFeatures and it is called just before bootmgr!BlBdStop in bootmgr!ArchExecuteTransition.