Commit 0081fdec authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Ingo Molnar
Browse files

x86/mm: Drop support for CONFIG_HIGHPTE 



With the maximum amount of RAM now 4GB, there is very little point
to still have PTE pages in highmem. Drop this for simplification.

The only other architecture supporting HIGHPTE is 32-bit arm, and
once that feature is removed as well, the highpte logic can be
dropped from common code as well.

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250226213714.4040853-8-arnd@kernel.org
parent a8331594

Documentation/admin-guide/kernel-parameters.txt

+0 −7
Original line number Diff line number Diff line
@@ -7668,13 +7668,6 @@ 
				16 - SIGBUS faults

			Example: user_debug=31



	userpte=

			[X86,EARLY] Flags controlling user PTE allocations.



				nohigh = do not allocate PTE pages in

					HIGHMEM regardless of setting

					of CONFIG_HIGHPTE.



	vdso=		[X86,SH,SPARC]

			On X86_32, this is an alias for vdso32=.  Otherwise:

arch/x86/Kconfig

+0 −9
Original line number Diff line number Diff line
@@ -1628,15 +1628,6 @@ config X86_PMEM_LEGACY 


	  Say Y if unsure.



config HIGHPTE

	bool "Allocate 3rd-level pagetables from highmem"

	depends on HIGHMEM

	help

	  The VM uses one page table entry for each page of physical memory.

	  For systems with a lot of RAM, this can be wasteful of precious

	  low memory.  Setting this option will put user-space page table

	  entries in high memory.



config X86_CHECK_BIOS_CORRUPTION

	bool "Check for low memory corruption"

	help

arch/x86/include/asm/pgalloc.h

+0 −5
Original line number Diff line number Diff line
@@ -29,11 +29,6 @@ static inline void paravirt_release_pud(unsigned long pfn) {} 
static inline void paravirt_release_p4d(unsigned long pfn) {}

#endif



/*

 * Flags to use when allocating a user page table page.

 */

extern gfp_t __userpte_alloc_gfp;



#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION

/*

 * Instead of one PGD, we acquire two PGDs.  Being order-1, it is

arch/x86/mm/pgtable.c

+1 −26
Original line number Diff line number Diff line
@@ -12,35 +12,10 @@ phys_addr_t physical_mask __ro_after_init = (1ULL << __PHYSICAL_MASK_SHIFT) - 1; 
EXPORT_SYMBOL(physical_mask);

#endif



#ifdef CONFIG_HIGHPTE

#define PGTABLE_HIGHMEM __GFP_HIGHMEM

#else

#define PGTABLE_HIGHMEM 0

#endif



gfp_t __userpte_alloc_gfp = GFP_PGTABLE_USER | PGTABLE_HIGHMEM;



pgtable_t pte_alloc_one(struct mm_struct *mm)

{

	return __pte_alloc_one(mm, __userpte_alloc_gfp);

}



static int __init setup_userpte(char *arg)

{

	if (!arg)

		return -EINVAL;



	/*

	 * "userpte=nohigh" disables allocation of user pagetables in

	 * high memory.

	 */

	if (strcmp(arg, "nohigh") == 0)

		__userpte_alloc_gfp &= ~__GFP_HIGHMEM;

	else

		return -EINVAL;

	return 0;

	return __pte_alloc_one(mm, GFP_PGTABLE_USER);

}

early_param("userpte", setup_userpte);



void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)

{