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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: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250226213714.4040853-8-arnd@kernel.org
This commit is contained in:
Arnd Bergmann 2025-02-26 22:37:11 +01:00 committed by Ingo Molnar
parent a833159403
commit 0081fdeccb
4 changed files with 1 additions and 47 deletions
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7
Documentation/admin-guide/kernel-parameters.txt
View File

@ -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:

9
arch/x86/Kconfig
View File

@ -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

5
arch/x86/include/asm/pgalloc.h
View File

@ -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

27
arch/x86/mm/pgtable.c
View File

@ -12,36 +12,11 @@ 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);
return __pte_alloc_one(mm, GFP_PGTABLE_USER);
}
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;
}
early_param("userpte", setup_userpte);
void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
{
paravirt_release_pte(page_to_pfn(pte));