[PATCH v12 4/5] arm64: Implement page table free interfaces

[Chintan Pandya]

Implement pud_free_pmd_page() and pmd_free_pte_page().

Implementation requires,
 1) Clearing off the current pud/pmd entry
 2) Invalidate TLB which could have previously
    valid but not stale entry
 3) Freeing of the un-used next level page tables

Signed-off-by: Chintan Pandya <cpandya@xxxxxxxxxxxxxx>
---
 arch/arm64/mm/mmu.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 8ae5d7a..6e7e16c 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -45,6 +45,7 @@
 #include <asm/memblock.h>
 #include <asm/mmu_context.h>
 #include <asm/ptdump.h>
+#include <asm/tlbflush.h>
 
 #define NO_BLOCK_MAPPINGS	BIT(0)
 #define NO_CONT_MAPPINGS	BIT(1)
@@ -977,12 +978,41 @@ int pmd_clear_huge(pmd_t *pmdp)
 	return 1;
 }
 
-int pud_free_pmd_page(pud_t *pud, unsigned long addr)
+int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
 {
-	return pud_none(*pud);
+	pte_t *table;
+	pmd_t pmd;
+
+	pmd = READ_ONCE(*pmdp);
+	if (pmd_present(pmd)) {
+		table = pmd_page_vaddr(pmd);
+		pmd_clear(pmdp);
+		__flush_tlb_kernel_pgtable(addr);
+		pte_free_kernel(NULL, table);
+	}
+	return 1;
 }
 
-int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
+int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
 {
-	return pmd_none(*pmd);
+	pmd_t *table;
+	pmd_t *entry;
+	pud_t pud;
+	unsigned long next, end;
+
+	pud = READ_ONCE(*pudp);
+	if (pud_present(pud)) {
+		table = pud_page_vaddr(pud);
+		entry = table;
+		next = addr;
+		end = addr + PUD_SIZE;
+		do {
+			pmd_free_pte_page(entry, next);
+		} while (entry++, next += PMD_SIZE, next != end);
+
+		pud_clear(pudp);
+		__flush_tlb_kernel_pgtable(addr);
+		pmd_free(NULL, table);
+	}
+	return 1;
 }
-- 
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