Re: [RFC V1 01/16] mm: Abstract printing of pxd_val()

Usama Arif
2026-02-26T12:35:21Z

On Tue, 24 Feb 2026 10:41:38 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:

> Ahead of adding support for D128 pgtables, refactor places that print
> PTE values to use the new __PRIpte format specifier and __PRIpte_args()
> macro to prepare the argument(s). When using D128 pgtables in future,
> we can simply redefine __PRIpte and __PTIpte_args().
>
> Besides there is also an assumption about pxd_val() being always capped
> at 'unsigned long long' size but that will not work for D128 pgtables.
> Just increase its size to u128 if the compiler supports via a separate
> data type pxdval_t which also defaults to existing 'unsigned long long'.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> include/linux/pgtable.h | 5 +++++
> mm/memory.c | 29 +++++++++++++++++++----------
> 2 files changed, 24 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index a50df42a893f..da17139a1279 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -17,6 +17,11 @@
> #include <asm-generic/pgtable_uffd.h>
> #include <linux/page_table_check.h>
>
> +#ifndef __PRIpte
> +#define __PRIpte "016llx"
> +#define __PRIpte_args(val) ((u64)val)
> +#endif
> +
> #if 5 - defined(__PAGETABLE_P4D_FOLDED) - defined(__PAGETABLE_PUD_FOLDED) - \
> defined(__PAGETABLE_PMD_FOLDED) != CONFIG_PGTABLE_LEVELS
> #error CONFIG_PGTABLE_LEVELS is not consistent with __PAGETABLE_{P4D,PUD,PMD}_FOLDED
> diff --git a/mm/memory.c b/mm/memory.c
> index 07778814b4a8..cfc3077fc52f 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -532,9 +532,15 @@ static bool is_bad_page_map_ratelimited(void)
> return false;
> }
>
> +#ifdef __SIZEOF_INT128__
> + typedef u128 pxdval_t;
> +#else
> + typedef unsigned long long pxdval_t;
> +#endif
> +
> static void __print_bad_page_map_pgtable(struct mm_struct *mm, unsigned long addr)
> {
> - unsigned long long pgdv, p4dv, pudv, pmdv;
> + pxdval_t pgdv, p4dv, pudv, pmdv;
> p4d_t p4d, *p4dp;
> pud_t pud, *pudp;
> pmd_t pmd, *pmdp;
> @@ -548,7 +554,7 @@ static void __print_bad_page_map_pgtable(struct mm_struct *mm, unsigned long add
> pgdv = pgd_val(*pgdp);
>
> if (!pgd_present(*pgdp) || pgd_leaf(*pgdp)) {
> - pr_alert("pgd:%08llx\n", pgdv);
> + pr_alert("pgd:%" __PRIpte "\n", __PRIpte_args(pgdv));
> return;
> }
>
> @@ -557,7 +563,8 @@ static void __print_bad_page_map_pgtable(struct mm_struct *mm, unsigned long add
> p4dv = p4d_val(p4d);
>
> if (!p4d_present(p4d) || p4d_leaf(p4d)) {
> - pr_alert("pgd:%08llx p4d:%08llx\n", pgdv, p4dv);
> + pr_alert("pgd:%" __PRIpte "p4d:%" __PRIpte "\n",

Hi Anshuman,

The original format had a space between values ("pgd:%08llx p4d:%08llx").
The replacement loses the space separator producing output like
"pgd:123p4d:456" instead of "pgd:123 p4d:456". The same issue exists
in other places in this commit.

> + __PRIpte_args(pgdv), __PRIpte_args(p4dv));
> return;
> }
>
> @@ -566,7 +573,8 @@ static void __print_bad_page_map_pgtable(struct mm_struct *mm, unsigned long add
> pudv = pud_val(pud);
>
> if (!pud_present(pud) || pud_leaf(pud)) {
> - pr_alert("pgd:%08llx p4d:%08llx pud:%08llx\n", pgdv, p4dv, pudv);
> + pr_alert("pgd:%" __PRIpte "p4d:%" __PRIpte "pud:%" __PRIpte "\n",
> + __PRIpte_args(pgdv), __PRIpte_args(p4dv), __PRIpte_args(pudv));
> return;
> }
>
> @@ -580,8 +588,9 @@ static void __print_bad_page_map_pgtable(struct mm_struct *mm, unsigned long add
> * doing another map would be bad. print_bad_page_map() should
> * already take care of printing the PTE.
> */
> - pr_alert("pgd:%08llx p4d:%08llx pud:%08llx pmd:%08llx\n", pgdv,
> - p4dv, pudv, pmdv);
> + pr_alert("pgd:%" __PRIpte "p4d:%" __PRIpte "pud:%" __PRIpte "pmd:%" __PRIpte "\n",
> + __PRIpte_args(pgdv), __PRIpte_args(p4dv),
> + __PRIpte_args(pudv), __PRIpte_args(pmdv));
> }
>
> /*
> @@ -597,7 +606,7 @@ static void __print_bad_page_map_pgtable(struct mm_struct *mm, unsigned long add
> * page table lock.
> */
> static void print_bad_page_map(struct vm_area_struct *vma,
> - unsigned long addr, unsigned long long entry, struct page *page,
> + unsigned long addr, pxdval_t entry, struct page *page,
> enum pgtable_level level)
> {
> struct address_space *mapping;
> @@ -609,8 +618,8 @@ static void print_bad_page_map(struct vm_area_struct *vma,
> mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
> index = linear_page_index(vma, addr);
>
> - pr_alert("BUG: Bad page map in process %s %s:%08llx", current->comm,
> - pgtable_level_to_str(level), entry);
> + pr_alert("BUG: Bad page map in process %s %s:%" __PRIpte, current->comm,
> + pgtable_level_to_str(level), __PRIpte_args(entry));
> __print_bad_page_map_pgtable(vma->vm_mm, addr);
> if (page)
> dump_page(page, "bad page map");
> @@ -695,7 +704,7 @@ static void print_bad_page_map(struct vm_area_struct *vma,
> */
> static inline struct page *__vm_normal_page(struct vm_area_struct *vma,
> unsigned long addr, unsigned long pfn, bool special,
> - unsigned long long entry, enum pgtable_level level)
> + pxdval_t entry, enum pgtable_level level)
> {
> if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
> if (unlikely(special)) {
> --
> 2.43.0
>
>