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

Anshuman Khandual
2026-02-26T12:50:02Z

On 26/02/26 6:04 PM, Usama Arif wrote:
> 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.

There needs to be a forward single space before p4d starts.

pr_alert("pgd:%" __PRIpte " p4d:%" __PRIpte "\n"

^^^
Will fix all the instances.

>
>> + __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
>>
>>