Let's introduce vm_normal_page_pud(), which ends up being fairly simple
because of our new common helpers and there not being a PUD-sized zero
folio.
Use vm_normal_page_pud() in folio_walk_start() to resolve a TODO,
structuring the code like the other (pmd/pte) cases. Defer
introducing vm_normal_folio_pud() until really used.
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/mm.h | 2 ++
mm/memory.c | 27 +++++++++++++++++++++++++++
mm/pagewalk.c | 20 ++++++++++----------
3 files changed, 39 insertions(+), 10 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index abc47f1f307fb..0eb991262fbbf 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2349,6 +2349,8 @@ struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma,
unsigned long addr, pmd_t pmd);
struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t pmd);
+struct page *vm_normal_page_pud(struct vm_area_struct *vma, unsigned long addr,
+ pud_t pud);
void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
unsigned long size);
diff --git a/mm/memory.c b/mm/memory.c
index c43ae5e4d7644..00a0d7ae3ba4a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -796,6 +796,33 @@ struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma,
return page_folio(page);
return NULL;
}
+
+/**
+ * vm_normal_page_pud() - Get the "struct page" associated with a PUD
+ * @vma: The VMA mapping the @pud.
+ * @addr: The address where the @pud is mapped.
+ * @pud: The PUD.
+ *
+ * Get the "struct page" associated with a PUD. See vm_normal_page_pfn()
+ * for details.
+ *
+ * Return: Returns the "struct page" if this is a "normal" mapping. Returns
+ * NULL if this is a "special" mapping.
+ */
+struct page *vm_normal_page_pud(struct vm_area_struct *vma,
+ unsigned long addr, pud_t pud)
+{
+ unsigned long pfn = pud_pfn(pud);
+
+ if (unlikely(pud_special(pud))) {
+ if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
+ return NULL;
+
+ print_bad_page_map(vma, addr, pud_val(pud), NULL);
+ return NULL;
+ }
+ return vm_normal_page_pfn(vma, addr, pfn, pud_val(pud));
+}
#endif
/**
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 648038247a8d2..c6753d370ff4e 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -902,23 +902,23 @@ struct folio *folio_walk_start(struct folio_walk *fw,
fw->pudp = pudp;
fw->pud = pud;
- /*
- * TODO: FW_MIGRATION support for PUD migration entries
- * once there are relevant users.
- */
- if (!pud_present(pud) || pud_special(pud)) {
+ if (pud_none(pud)) {
spin_unlock(ptl);
goto not_found;
- } else if (!pud_leaf(pud)) {
+ } else if (pud_present(pud) && !pud_leaf(pud)) {
spin_unlock(ptl);
goto pmd_table;
+ } else if (pud_present(pud)) {
+ page = vm_normal_page_pud(vma, addr, pud);
+ if (page)
+ goto found;
}
/*
- * TODO: vm_normal_page_pud() will be handy once we want to
- * support PUD mappings in VM_PFNMAP|VM_MIXEDMAP VMAs.
+ * TODO: FW_MIGRATION support for PUD migration entries
+ * once there are relevant users.
*/
- page = pud_page(pud);
- goto found;
+ spin_unlock(ptl);
+ goto not_found;
}
pmd_table:
--
2.50.1On Thu, Jul 17, 2025 at 01:52:11PM +0200, David Hildenbrand wrote: >Let's introduce vm_normal_page_pud(), which ends up being fairly simple >because of our new common helpers and there not being a PUD-sized zero >folio. > >Use vm_normal_page_pud() in folio_walk_start() to resolve a TODO, >structuring the code like the other (pmd/pte) cases. Defer >introducing vm_normal_folio_pud() until really used. > >Reviewed-by: Oscar Salvador <osalvador@suse.de> >Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Wei Yang <richard.weiyang@gmail.com> -- Wei Yang Help you, Help me
On Thu, Jul 17, 2025 at 01:52:11PM +0200, David Hildenbrand wrote:
> Let's introduce vm_normal_page_pud(), which ends up being fairly simple
> because of our new common helpers and there not being a PUD-sized zero
> folio.
>
> Use vm_normal_page_pud() in folio_walk_start() to resolve a TODO,
> structuring the code like the other (pmd/pte) cases. Defer
> introducing vm_normal_folio_pud() until really used.
I mean fine :P but does anybody really use this?
>
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> Signed-off-by: David Hildenbrand <david@redhat.com>
Seems ok to me, so:
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> ---
> include/linux/mm.h | 2 ++
> mm/memory.c | 27 +++++++++++++++++++++++++++
> mm/pagewalk.c | 20 ++++++++++----------
> 3 files changed, 39 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index abc47f1f307fb..0eb991262fbbf 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2349,6 +2349,8 @@ struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma,
> unsigned long addr, pmd_t pmd);
> struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
> pmd_t pmd);
> +struct page *vm_normal_page_pud(struct vm_area_struct *vma, unsigned long addr,
> + pud_t pud);
>
> void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
> unsigned long size);
> diff --git a/mm/memory.c b/mm/memory.c
> index c43ae5e4d7644..00a0d7ae3ba4a 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -796,6 +796,33 @@ struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma,
> return page_folio(page);
> return NULL;
> }
> +
> +/**
> + * vm_normal_page_pud() - Get the "struct page" associated with a PUD
> + * @vma: The VMA mapping the @pud.
> + * @addr: The address where the @pud is mapped.
> + * @pud: The PUD.
> + *
> + * Get the "struct page" associated with a PUD. See vm_normal_page_pfn()
> + * for details.
> + *
> + * Return: Returns the "struct page" if this is a "normal" mapping. Returns
> + * NULL if this is a "special" mapping.
> + */
> +struct page *vm_normal_page_pud(struct vm_area_struct *vma,
> + unsigned long addr, pud_t pud)
> +{
> + unsigned long pfn = pud_pfn(pud);
> +
> + if (unlikely(pud_special(pud))) {
> + if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
> + return NULL;
> +
> + print_bad_page_map(vma, addr, pud_val(pud), NULL);
> + return NULL;
> + }
> + return vm_normal_page_pfn(vma, addr, pfn, pud_val(pud));
> +}
> #endif
>
> /**
> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
> index 648038247a8d2..c6753d370ff4e 100644
> --- a/mm/pagewalk.c
> +++ b/mm/pagewalk.c
> @@ -902,23 +902,23 @@ struct folio *folio_walk_start(struct folio_walk *fw,
> fw->pudp = pudp;
> fw->pud = pud;
>
> - /*
> - * TODO: FW_MIGRATION support for PUD migration entries
> - * once there are relevant users.
> - */
> - if (!pud_present(pud) || pud_special(pud)) {
> + if (pud_none(pud)) {
> spin_unlock(ptl);
> goto not_found;
> - } else if (!pud_leaf(pud)) {
> + } else if (pud_present(pud) && !pud_leaf(pud)) {
> spin_unlock(ptl);
> goto pmd_table;
> + } else if (pud_present(pud)) {
> + page = vm_normal_page_pud(vma, addr, pud);
> + if (page)
> + goto found;
> }
> /*
> - * TODO: vm_normal_page_pud() will be handy once we want to
> - * support PUD mappings in VM_PFNMAP|VM_MIXEDMAP VMAs.
> + * TODO: FW_MIGRATION support for PUD migration entries
> + * once there are relevant users.
> */
> - page = pud_page(pud);
> - goto found;
> + spin_unlock(ptl);
> + goto not_found;
> }
>
> pmd_table:
> --
> 2.50.1
>
On 17.07.25 22:03, Lorenzo Stoakes wrote: > On Thu, Jul 17, 2025 at 01:52:11PM +0200, David Hildenbrand wrote: >> Let's introduce vm_normal_page_pud(), which ends up being fairly simple >> because of our new common helpers and there not being a PUD-sized zero >> folio. >> >> Use vm_normal_page_pud() in folio_walk_start() to resolve a TODO, >> structuring the code like the other (pmd/pte) cases. Defer >> introducing vm_normal_folio_pud() until really used. > > I mean fine :P but does anybody really use this? This is a unified PFN walker (!hugetlb + hugetlb), so you can easily run into hugetlb PUDs, DAX PUDs and huge pfnmap (vfio) PUDs :) -- Cheers, David / dhildenb
On Thu, Jul 17, 2025 at 10:14:33PM +0200, David Hildenbrand wrote: > On 17.07.25 22:03, Lorenzo Stoakes wrote: > > On Thu, Jul 17, 2025 at 01:52:11PM +0200, David Hildenbrand wrote: > > > Let's introduce vm_normal_page_pud(), which ends up being fairly simple > > > because of our new common helpers and there not being a PUD-sized zero > > > folio. > > > > > > Use vm_normal_page_pud() in folio_walk_start() to resolve a TODO, > > > structuring the code like the other (pmd/pte) cases. Defer > > > introducing vm_normal_folio_pud() until really used. > > > > I mean fine :P but does anybody really use this? > > This is a unified PFN walker (!hugetlb + hugetlb), so you can easily run > into hugetlb PUDs, DAX PUDs and huge pfnmap (vfio) PUDs :) Ahhh ok. I hate hugetlb so very very much. Oscar is doing the Lord's work improving things but the trauma is still there... :P Also yeah DAX ahem. I'm not familiar with huge pfnmap PUDs, could you give me a hint on this? :>) > > -- > Cheers, > > David / dhildenb >
On 18.07.25 12:47, Lorenzo Stoakes wrote: > On Thu, Jul 17, 2025 at 10:14:33PM +0200, David Hildenbrand wrote: >> On 17.07.25 22:03, Lorenzo Stoakes wrote: >>> On Thu, Jul 17, 2025 at 01:52:11PM +0200, David Hildenbrand wrote: >>>> Let's introduce vm_normal_page_pud(), which ends up being fairly simple >>>> because of our new common helpers and there not being a PUD-sized zero >>>> folio. >>>> >>>> Use vm_normal_page_pud() in folio_walk_start() to resolve a TODO, >>>> structuring the code like the other (pmd/pte) cases. Defer >>>> introducing vm_normal_folio_pud() until really used. >>> >>> I mean fine :P but does anybody really use this? >> >> This is a unified PFN walker (!hugetlb + hugetlb), so you can easily run >> into hugetlb PUDs, DAX PUDs and huge pfnmap (vfio) PUDs :) > > Ahhh ok. I hate hugetlb so very very much. > > Oscar is doing the Lord's work improving things but the trauma is still > there... :P > > Also yeah DAX ahem. > > I'm not familiar with huge pfnmap PUDs, could you give me a hint on this? :>) vmf_insert_pfn_pmd(), called from drivers/vfio/pci/vfio_pci_core.c Essentially, we create huge PUDs when mapping device BARs to user space. -- Cheers, David / dhildenb
On Fri, Jul 18, 2025 at 01:06:30PM +0200, David Hildenbrand wrote: > On 18.07.25 12:47, Lorenzo Stoakes wrote: > > On Thu, Jul 17, 2025 at 10:14:33PM +0200, David Hildenbrand wrote: > > > On 17.07.25 22:03, Lorenzo Stoakes wrote: > > > > On Thu, Jul 17, 2025 at 01:52:11PM +0200, David Hildenbrand wrote: > > > > > Let's introduce vm_normal_page_pud(), which ends up being fairly simple > > > > > because of our new common helpers and there not being a PUD-sized zero > > > > > folio. > > > > > > > > > > Use vm_normal_page_pud() in folio_walk_start() to resolve a TODO, > > > > > structuring the code like the other (pmd/pte) cases. Defer > > > > > introducing vm_normal_folio_pud() until really used. > > > > > > > > I mean fine :P but does anybody really use this? > > > > > > This is a unified PFN walker (!hugetlb + hugetlb), so you can easily run > > > into hugetlb PUDs, DAX PUDs and huge pfnmap (vfio) PUDs :) > > > > Ahhh ok. I hate hugetlb so very very much. > > > > Oscar is doing the Lord's work improving things but the trauma is still > > there... :P > > > > Also yeah DAX ahem. > > > > I'm not familiar with huge pfnmap PUDs, could you give me a hint on this? :>) > > vmf_insert_pfn_pmd(), called from drivers/vfio/pci/vfio_pci_core.c > > Essentially, we create huge PUDs when mapping device BARs to user space. Ah makes sense. Thanks!
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