The #ifdef around pud_clear() is very weird, but needed to

compile bootstrapping arch/x86/boot/compressed/error.c,

which arch/x86/boot/compressed/misc.h does

#undef CONFIG_PARAVIRT

and codepath inside arch/x86/include/asm/pgtable.h

goes into generally unused codepath, which does

#ifndef __PAGETABLE_PMD_FOLDED	/* never defined */

#define pud_clear(pud)                  native_pud_clear(pud)

#endif

which will duplicate define pud_clear().

diff -up ./arch/x86/include/asm/pgtable-3level.h.pud ./arch/x86/include/asm/pgtable-3level.h

--- ./arch/x86/include/asm/pgtable-3level.h.pud	2018-11-02 13:21:03.000000000 +0900

+++ ./arch/x86/include/asm/pgtable-3level.h	2018-11-02 13:20:08.000000000 +0900

@@ -129,12 +129,11 @@ static inline void native_pmd_clear(pmd_

 	*(tmp + 1) = 0;

 }

-#ifndef CONFIG_SMP

 static inline void native_pud_clear(pud_t *pudp)

 {

 }

-#endif

+#if /*defined(__PAGETABLE_PMD_FOLDED) &&*/ defined(CONFIG_PARAVIRT)

 static inline void pud_clear(pud_t *pudp)

 {

 	mm_track_pud(pudp);

@@ -151,6 +150,7 @@ static inline void pud_clear(pud_t *pudp

 	 * pud_clear_bad()), so we don't need TLB flush here.

 	 */

 }

+#endif

 #ifdef CONFIG_SMP

 static inline pte_t native_ptep_get_and_clear(pte_t *ptep)