HV: enable SMEP in hypervisor

- this patch is to enable SMEP in hypervisor, SMEP protects
   guests' memory from supervisor-mode instruction fetches,
   in other words, hypervisor which operating in supervisor
   mode can't fetch instructions from (guests' memory)
   linear addresses that are accessible in user mode.

Signed-off-by: Yonghua Huang <yonghua.huang@intel.com>

hypervisor/include/arch/x86/cpu.h

@@ -84,6 +84,8 @@
 #define CR4_SMXE                (1<<14)	/* SMX enable */
 #define CR4_PCIDE               (1<<17)	/* PCID enable */
 #define CR4_OSXSAVE             (1<<18)
+#define CR4_SMEP                (1<<20)
+#define CR4_SMAP                (1<<21)
 /* XSAVE and Processor Extended States enable bit */
 
 

hypervisor/include/arch/x86/mmu.h

@@ -299,6 +299,7 @@ bool check_mmu_1gb_support(int page_table_type);
 void *alloc_paging_struct(void);
 void free_paging_struct(void *ptr);
 void enable_paging(uint64_t pml4_base_addr);
+void enable_smep(void);
 void init_paging(void);
 int map_mem(struct map_params *map_params, void *paddr, void *vaddr,
 		    uint64_t size, uint32_t flags);