arm64: mm: Drop dead code for pud special bit handling

JIRA: https://issues.redhat.com/browse/RHEL-101059

commit 0fff2aa
Author: Peter Xu <peterx@redhat.com>
Date: Thu, 20 Mar 2025 14:34:05 -0400

    Keith Busch observed some incorrect macros defined in arm64 code [1].

    It turns out the two lines should never be needed and won't be exposed to
    anyone, because aarch64 doesn't select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD,
    hence ARCH_SUPPORTS_PUD_PFNMAP is always N.  The only archs that support
    THP PUDs so far are x86 and powerpc.

    Instead of fixing the lines (with no way to test it..), remove the two
    lines that are in reality dead code, to avoid confusing readers.

    Fixes tag is attached to reflect where the wrong macros were introduced,
    but explicitly not copying stable, because there's no real issue to be
    fixed.  So it's only about removing the dead code so far.

    [1] https://lore.kernel.org/all/Z9tDjOk-JdV_fCY4@kbusch-mbp.dhcp.thefacebook.com/#t

    Cc: Alex Williamson <alex.williamson@redhat.com>
    Cc: Donald Dutile <ddutile@redhat.com>
    Cc: Will Deacon <will@kernel.org>
    Fixes: 3e509c9 ("mm/arm64: support large pfn mappings")
    Reported-by: Keith Busch <kbusch@kernel.org>
    Signed-off-by: Peter Xu <peterx@redhat.com>
    Reviewed-by: Donald Dutile <ddutile@redhat.com>
    Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
    Link: https://lore.kernel.org/r/20250320183405.12659-1-peterx@redhat.com
    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Signed-off-by: Mark Salter <msalter@redhat.com>

Author: mosalter

arch/arm64/include/asm/pgtable.h

@@ -633,11 +633,6 @@ static inline pud_t pud_mkhuge(pud_t pud)
 #define pud_pfn(pud)		((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT)
 #define pfn_pud(pfn,prot)	__pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
 
-#ifdef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP
-#define pud_special(pte)	pte_special(pud_pte(pud))
-#define pud_mkspecial(pte)	pte_pud(pte_mkspecial(pud_pte(pud)))
-#endif
-
 #define pmd_pgprot pmd_pgprot
 static inline pgprot_t pmd_pgprot(pmd_t pmd)
 {