[PATCH 05/22] arm64: mm: use mm_is_kernel() for kernel mm checks

From: Kevin Brodsky <hidden>
Date: 2026-07-14 14:05:49
Also in: linux-arch, linux-efi, linux-mm, linux-riscv, linux-s390, linux-um, lkml, loongarch, sparclinux
Reply to: Kevin Brodsky, 2026-07-14

The new MMF_KERNEL flag identifies kernel-owned mm's. Checking the
flag with mm_is_kernel() is preferred over comparing directly
against &init_mm.

In some cases, such as show_pte(), the handling is truly specific to
init_mm and we leave those comparisons with &init_mm unchanged.

No functional change, as only init_mm has MMF_KERNEL set for now.

mm_is_user() will eventually be replaced with !mm_is_kernel(), once
efi_mm is also marked with MMF_KERNEL.

Assisted-by: Codex:GPT-5.5
Signed-off-by: Kevin Brodsky <redacted>
---
 arch/arm64/include/asm/pgalloc.h | 10 +++++-----
 arch/arm64/mm/contpte.c          |  2 +-
 arch/arm64/mm/hugetlbpage.c      |  2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
index 1b4509d3382c..33db4fa3c619 100644
--- a/arch/arm64/include/asm/pgalloc.h
+++ b/arch/arm64/include/asm/pgalloc.h

@@ -30,7 +30,7 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp)
 {
 	pudval_t pudval = PUD_TYPE_TABLE | PUD_TABLE_AF;
 
-	pudval |= (mm == &init_mm) ? PUD_TABLE_UXN : PUD_TABLE_PXN;
+	pudval |= mm_is_kernel(mm) ? PUD_TABLE_UXN : PUD_TABLE_PXN;
 	__pud_populate(pudp, __pa(pmdp), pudval);
 }
 #else

@@ -52,7 +52,7 @@ static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4dp, pud_t *pudp)
 {
 	p4dval_t p4dval = P4D_TYPE_TABLE | P4D_TABLE_AF;
 
-	p4dval |= (mm == &init_mm) ? P4D_TABLE_UXN : P4D_TABLE_PXN;
+	p4dval |= mm_is_kernel(mm) ? P4D_TABLE_UXN : P4D_TABLE_PXN;
 	__p4d_populate(p4dp, __pa(pudp), p4dval);
 }

@@ -81,7 +81,7 @@ static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgdp, p4d_t *p4dp)
 {
 	pgdval_t pgdval = PGD_TYPE_TABLE | PGD_TABLE_AF;
 
-	pgdval |= (mm == &init_mm) ? PGD_TABLE_UXN : PGD_TABLE_PXN;
+	pgdval |= mm_is_kernel(mm) ? PGD_TABLE_UXN : PGD_TABLE_PXN;
 	__pgd_populate(pgdp, __pa(p4dp), pgdval);
 }

@@ -108,7 +108,7 @@ static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t ptep,
 static inline void
 pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmdp, pte_t *ptep)
 {
-	VM_BUG_ON(mm && mm != &init_mm);
+	VM_BUG_ON(mm && !mm_is_kernel(mm));
 	__pmd_populate(pmdp, __pa(ptep),
 		       PMD_TYPE_TABLE | PMD_TABLE_AF | PMD_TABLE_UXN);
 }

@@ -116,7 +116,7 @@ pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmdp, pte_t *ptep)
 static inline void
 pmd_populate(struct mm_struct *mm, pmd_t *pmdp, pgtable_t ptep)
 {
-	VM_BUG_ON(mm == &init_mm);
+	VM_BUG_ON(mm_is_kernel(mm));
 	__pmd_populate(pmdp, page_to_phys(ptep),
 		       PMD_TYPE_TABLE | PMD_TABLE_AF | PMD_TABLE_PXN);
 }

diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
index 2de12656b4d8..ad5c04cf66ff 100644
--- a/arch/arm64/mm/contpte.c
+++ b/arch/arm64/mm/contpte.c

@@ -18,7 +18,7 @@ static inline bool mm_is_user(struct mm_struct *mm)
 	 */
 	if (unlikely(mm_is_efi(mm)))
 		return false;
-	return mm != &init_mm;
+	return !mm_is_kernel(mm);
 }
 
 static inline pte_t *contpte_align_down(pte_t *ptep)

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 25f04d01aabe..4d054fadf51c 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c

@@ -212,7 +212,7 @@ static void clear_flush(struct mm_struct *mm,
 	for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
 		__ptep_get_and_clear_anysz(mm, addr, ptep, pgsize);
 
-	if (mm == &init_mm)
+	if (mm_is_kernel(mm))
 		flush_tlb_kernel_range(saddr, addr);
 	else
 		__flush_hugetlb_tlb_range(&vma, saddr, addr, pgsize, TLBF_NOWALKCACHE);

-- 
2.51.2

Kevin Brodsky · 2026-07-14
[PATCH 01/22] mm: drop unused __mm_flags_set_mask_bits_word() · Kevin Brodsky · 2026-07-14
Re: [PATCH 01/22] mm: drop unused __mm_flags_set_mask_bits_word() · David Hildenbrand (Arm) · 2026-07-21
[PATCH 02/22] mm: move mm_flags helpers to mm_types.h · Kevin Brodsky · 2026-07-14
Re: [PATCH 02/22] mm: move mm_flags helpers to mm_types.h · David Hildenbrand (Arm) · 2026-07-21
[PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · Kevin Brodsky · 2026-07-14
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · Dave Hansen · 2026-07-14
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · Lorenzo Stoakes (ARM) · 2026-07-14
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · Kevin Brodsky · 2026-07-16
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · David Hildenbrand (Arm) · 2026-07-21
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · Kevin Brodsky · 2026-07-24
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · Christophe Leroy (CS GROUP) · 2026-08-03
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · David Hildenbrand (Arm) · 2026-08-05
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · Kevin Brodsky · 2026-08-10
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · David Laight · 2026-08-11
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · Kevin Brodsky · 2026-08-11
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · David Laight · 2026-08-11
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · David Laight · 2026-08-11
Re: [PATCH 03/22] mm: introduce MMF_KERNEL flag and set it for init_mm · Kevin Brodsky · 2026-08-11
[PATCH 04/22] mm: use mm_is_kernel() in generic page table code · Kevin Brodsky · 2026-07-14
Re: [PATCH 04/22] mm: use mm_is_kernel() in generic page table code · Kevin Brodsky · 2026-07-16
Re: [PATCH 04/22] mm: use mm_is_kernel() in generic page table code · David Hildenbrand (Arm) · 2026-07-21
Re: [PATCH 04/22] mm: use mm_is_kernel() in generic page table code · Kevin Brodsky · 2026-07-24
[PATCH 05/22] arm64: mm: use mm_is_kernel() for kernel mm checks · Kevin Brodsky · 2026-07-14
[PATCH 06/22] loongarch: mm: use mm_is_kernel() in switch_mm_irqs_off() · Kevin Brodsky · 2026-07-14
[PATCH 07/22] parisc: mm: use mm_is_kernel() for kernel mm checks · Kevin Brodsky · 2026-07-14
[PATCH 08/22] powerpc: mm: use mm_is_kernel() for kernel mm checks · Kevin Brodsky · 2026-07-14
[PATCH 09/22] s390: mm: use mm_is_kernel() for kernel mm checks · Kevin Brodsky · 2026-07-14
[PATCH 10/22] sparc: mm: use mm_is_kernel() for kernel mm checks · Kevin Brodsky · 2026-07-14
[PATCH 11/22] um: mm: use mm_is_kernel() in TLB sync · Kevin Brodsky · 2026-07-14
[PATCH 12/22] x86/mm: use mm_is_kernel() for kernel mm checks · Kevin Brodsky · 2026-07-14
Re: [PATCH 12/22] x86/mm: use mm_is_kernel() for kernel mm checks · Dave Hansen · 2026-07-14
[PATCH 13/22] mm: account page table pages when allocated · Kevin Brodsky · 2026-07-14
[PATCH 14/22] mm: set page table page type when allocated · Kevin Brodsky · 2026-07-14
Re: [PATCH 14/22] mm: set page table page type when allocated · Vishal Moola · 2026-07-14
Re: [PATCH 14/22] mm: set page table page type when allocated · Kevin Brodsky · 2026-07-16
Re: [PATCH 14/22] mm: set page table page type when allocated · Vishal Moola · 2026-07-20
Re: [PATCH 14/22] mm: set page table page type when allocated · Kevin Brodsky · 2026-07-24
[PATCH 15/22] mm: only initialise pt_share_count for user pgtables · Kevin Brodsky · 2026-07-14
Re: [PATCH 15/22] mm: only initialise pt_share_count for user pgtables · David Hildenbrand (Arm) · 2026-07-21
Re: [PATCH 15/22] mm: only initialise pt_share_count for user pgtables · Kevin Brodsky · 2026-07-24
[PATCH 16/22] efi: mark efi_mm as a kernel mm · Kevin Brodsky · 2026-07-14
[PATCH 17/22] mm: pagewalk: drop redundant address check for kernel mm walks · Kevin Brodsky · 2026-07-14
Re: [PATCH 17/22] mm: pagewalk: drop redundant address check for kernel mm walks · Kevin Brodsky · 2026-07-16
[PATCH 18/22] arm64: mm: drop explicit mm_is_efi() check in contpte · Kevin Brodsky · 2026-07-14
[PATCH 19/22] x86/tboot: mark tboot_mm as a kernel mm · Kevin Brodsky · 2026-07-14
Re: [PATCH 19/22] x86/tboot: mark tboot_mm as a kernel mm · Dave Hansen · 2026-07-14
[PATCH 20/22] arm64: mm: drop ctor/dtor calls for kernel page tables · Kevin Brodsky · 2026-07-14
[PATCH 21/22] arm: mm: drop ctor call for kernel page tables · Kevin Brodsky · 2026-07-14
[PATCH 22/22] riscv: mm: drop ctor/dtor calls for kernel page tables · Kevin Brodsky · 2026-07-14
Kevin Brodsky · 2026-07-15
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