RE: [PATCH v3 1/1] iommu/sva: Invalidate KVA range on kernel TLB flush

From: Baolu Lu baolu.lu@linux.intel.com Sent: Thursday, August 28, 2025 1:31 PM

@@ -438,7 +438,10 @@ static void cpa_collapse_large_pages(struct cpa_data *cpa)

list_for_each_entry_safe(ptdesc, tmp, &pgtables, pt_list) { list_del(&ptdesc->pt_list);

• __free_page(ptdesc_page(ptdesc));
  

• if (IS_ENABLED(CONFIG_ASYNC_PGTABLE_FREE))
  

• 	kernel_pgtable_async_free(ptdesc);
  

• else
  

• 	__free_page(ptdesc_page(ptdesc));
  

  }

Dave's suggestion is to check the new ptdesc flag and defer in pagetable_free().

both here and above could be converted to:

ptdesc->__page_type |= PTDESC_TYPE_KERNEL; pagetable_free(ptdesc);

@@ -757,7 +757,14 @@ int pud_free_pmd_page(pud_t *pud, unsigned long addr)

free_page((unsigned long)pmd_sv);

• pmd_free(&init_mm, pmd);

• if (IS_ENABLED(CONFIG_ASYNC_PGTABLE_FREE)) {

• struct ptdesc *ptdesc = virt_to_ptdesc(pmd);
  

• ptdesc->__page_type |= PTDESC_TYPE_KERNEL;
  

• kernel_pgtable_async_free(ptdesc);
  

• } else {

• pmd_free(&init_mm, pmd);
  

• }

We may add a new pmd_free_kernel() helper, which does:

ptdesc->__page_type |= PTDESC_TYPE_KERNEL; pagetable_dtor_free(ptdesc);

static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte) {

• pagetable_dtor_free(virt_to_ptdesc(pte));

• struct ptdesc *ptdesc = virt_to_ptdesc(pte);
• ptdesc->__page_type |= PTDESC_TYPE_KERNEL;
• if (IS_ENABLED(CONFIG_ASYNC_PGTABLE_FREE))

• kernel_pgtable_async_free(ptdesc);
  

• else

• pagetable_dtor_free(ptdesc);
  

  }

same:

ptdesc->__page_type |= PTDESC_TYPE_KERNEL; pagetable_dtor_free(ptdesc);

Then you have pagetable_free() to handle defer in one place (revised on Dave's draft):

static inline void pagetable_free(struct ptdesc *pt) { struct page *page = ptdesc_page(pt);

if (IS_ENABLED(CONFIG_ASYNC_PGTABLE_FREE) && (ptdesc->__page_type | PTDESC_KERNEL)) kernel_pgtable_async_free_page(page); else __free_pages(page, compound_order(page)); }

+static void kernel_pgtable_work_func(struct work_struct *work) +{

• struct ptdesc *ptdesc, *next;
• LIST_HEAD(page_list);
• spin_lock(&kernel_pgtable_work.lock);
• list_splice_tail_init(&kernel_pgtable_work.list, &page_list);
• spin_unlock(&kernel_pgtable_work.lock);
• list_for_each_entry_safe(ptdesc, next, &page_list, pt_list) {

• list_del(&ptdesc->pt_list);
  

• if (ptdesc->__page_type & PTDESC_TYPE_KERNEL) {
  

• 	pagetable_dtor_free(ptdesc);
  

• } else {
  

• 	struct page *page = ptdesc_page(ptdesc);
  

• 	__free_pages(page, compound_order(page));
  

• }
  

Then you only need __free_pages() here.