1 #include <asm/processor.h>
2 
3 /*
4  * __force_order is used by special_insns.h asm code to force instruction
5  * serialization.
6  *
7  * It is not referenced from the code, but GCC < 5 with -fPIE would fail
8  * due to an undefined symbol. Define it to make these ancient GCCs work.
9  */
10 unsigned long __force_order;
11 
12 int l5_paging_required(void)
13 {
14 	/* Check if leaf 7 is supported. */
15 
16 	if (native_cpuid_eax(0) < 7)
17 		return 0;
18 
19 	/* Check if la57 is supported. */
20 	if (!(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31))))
21 		return 0;
22 
23 	/* Check if 5-level paging has already been enabled. */
24 	if (native_read_cr4() & X86_CR4_LA57)
25 		return 0;
26 
27 	return 1;
28 }
29