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Subject[RFC v2 11/26] mm/asi: Functions to clear ASI page-table entries for a VA range
Date
Provide functions to clear page-table entries in the ASI page-table for
a specified VA range. Functions also check that the clearing effectively
happens in the ASI page-table and there is no crossing of the ASI
page-table boundary (through references to the kernel page table), so
that the kernel page table is not modified by mistake.

As information (address, size, page-table level) about VA ranges mapped
to the ASI page-table is tracked, clearing is done with just specifying
the start address of the range.

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
arch/x86/include/asm/asi.h | 1 +
arch/x86/mm/asi_pagetable.c | 134 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 135 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h
index be1c190..919129f 100644
--- a/arch/x86/include/asm/asi.h
+++ b/arch/x86/include/asm/asi.h
@@ -83,6 +83,7 @@ extern bool asi_fault(struct pt_regs *regs, unsigned long error_code,
extern int asi_map_range(struct asi *asi, void *ptr, size_t size,
enum page_table_level level);
extern int asi_map(struct asi *asi, void *ptr, unsigned long size);
+extern void asi_unmap(struct asi *asi, void *ptr);

/*
* Copy the memory mapping for the current module. This is defined as a
diff --git a/arch/x86/mm/asi_pagetable.c b/arch/x86/mm/asi_pagetable.c
index a09a22d..7aee236 100644
--- a/arch/x86/mm/asi_pagetable.c
+++ b/arch/x86/mm/asi_pagetable.c
@@ -670,3 +670,137 @@ int asi_map(struct asi *asi, void *ptr, unsigned long size)
return asi_map_range(asi, ptr, size, PGT_LEVEL_PTE);
}
EXPORT_SYMBOL(asi_map);
+
+static void asi_clear_pte_range(struct asi *asi, pmd_t *pmd,
+ unsigned long addr, unsigned long end)
+{
+ pte_t *pte;
+
+ pte = asi_pte_offset(asi, pmd, addr);
+ if (IS_ERR(pte))
+ return;
+
+ do {
+ pte_clear(NULL, addr, pte);
+ } while (pte++, addr += PAGE_SIZE, addr < end);
+}
+
+static void asi_clear_pmd_range(struct asi *asi, pud_t *pud,
+ unsigned long addr, unsigned long end,
+ enum page_table_level level)
+{
+ unsigned long next;
+ pmd_t *pmd;
+
+ pmd = asi_pmd_offset(asi, pud, addr);
+ if (IS_ERR(pmd))
+ return;
+
+ do {
+ next = pmd_addr_end(addr, end);
+ if (pmd_none(*pmd) || pmd_present(*pmd))
+ continue;
+ if (level == PGT_LEVEL_PMD || pmd_trans_huge(*pmd) ||
+ pmd_devmap(*pmd)) {
+ pmd_clear(pmd);
+ continue;
+ }
+ asi_clear_pte_range(asi, pmd, addr, next);
+ } while (pmd++, addr = next, addr < end);
+}
+
+static void asi_clear_pud_range(struct asi *asi, p4d_t *p4d,
+ unsigned long addr, unsigned long end,
+ enum page_table_level level)
+{
+ unsigned long next;
+ pud_t *pud;
+
+ pud = asi_pud_offset(asi, p4d, addr);
+ if (IS_ERR(pud))
+ return;
+
+ do {
+ next = pud_addr_end(addr, end);
+ if (pud_none(*pud))
+ continue;
+ if (level == PGT_LEVEL_PUD || pud_trans_huge(*pud) ||
+ pud_devmap(*pud)) {
+ pud_clear(pud);
+ continue;
+ }
+ asi_clear_pmd_range(asi, pud, addr, next, level);
+ } while (pud++, addr = next, addr < end);
+}
+
+static void asi_clear_p4d_range(struct asi *asi, pgd_t *pgd,
+ unsigned long addr, unsigned long end,
+ enum page_table_level level)
+{
+ unsigned long next;
+ p4d_t *p4d;
+
+ p4d = asi_p4d_offset(asi, pgd, addr);
+ if (IS_ERR(p4d))
+ return;
+
+ do {
+ next = p4d_addr_end(addr, end);
+ if (p4d_none(*p4d))
+ continue;
+ if (level == PGT_LEVEL_P4D) {
+ p4d_clear(p4d);
+ continue;
+ }
+ asi_clear_pud_range(asi, p4d, addr, next, level);
+ } while (p4d++, addr = next, addr < end);
+}
+
+static void asi_clear_pgd_range(struct asi *asi, pgd_t *pagetable,
+ unsigned long addr, unsigned long end,
+ enum page_table_level level)
+{
+ unsigned long next;
+ pgd_t *pgd;
+
+ pgd = pgd_offset_pgd(pagetable, addr);
+ do {
+ next = pgd_addr_end(addr, end);
+ if (pgd_none(*pgd))
+ continue;
+ if (level == PGT_LEVEL_PGD) {
+ pgd_clear(pgd);
+ continue;
+ }
+ asi_clear_p4d_range(asi, pgd, addr, next, level);
+ } while (pgd++, addr = next, addr < end);
+}
+
+/*
+ * Clear page table entries in the specified ASI page-table.
+ */
+void asi_unmap(struct asi *asi, void *ptr)
+{
+ struct asi_range_mapping *range_mapping;
+ unsigned long addr, end;
+ unsigned long flags;
+
+ spin_lock_irqsave(&asi->lock, flags);
+
+ range_mapping = asi_get_range_mapping(asi, ptr);
+ if (!range_mapping) {
+ pr_debug("ASI %p: UNMAP %px - not mapped\n", asi, ptr);
+ goto done;
+ }
+
+ addr = (unsigned long)range_mapping->ptr;
+ end = addr + range_mapping->size;
+ pr_debug("ASI %p: UNMAP %px/%lx/%d\n", asi, ptr,
+ range_mapping->size, range_mapping->level);
+ asi_clear_pgd_range(asi, asi->pgd, addr, end, range_mapping->level);
+ list_del(&range_mapping->list);
+ kfree(range_mapping);
+done:
+ spin_unlock_irqrestore(&asi->lock, flags);
+}
+EXPORT_SYMBOL(asi_unmap);
--
1.7.1
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