arch/x86/boot/compressed/pgtable_64.c

   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 }