x86/VPMU: mark context LOADED before registers are loaded

x86/VPMU: mark context LOADED before registers are loaded

Because a PMU interrupt may be generated as soon as PMU registers are
loaded (or, more precisely, as soon as HW PMU is "armed") we don't want
to delay marking context as LOADED until after registers are loaded.
Otherwise during interrupt handling VPMU_CONTEXT_LOADED may not be set
and this could be confusing.

(Technically, only SVM needs this change right now since VMX will "arm"
PMU later, during VMRUN when global control register is loaded from
VMCS. However, both AMD and Intel code will require this patch when we
introduce PV VPMU.)

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Dietmar Hahn <dietmar.hahn@ts.fujitsu.com>
Tested-by: Dietmar Hahn <dietmar.hahn@ts.fujitsu.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>