On 6/4/2018 5:43 PM, Will Deacon wrote:

On Fri, Jun 01, 2018 at 06:09:17PM +0530, Chintan Pandya wrote:

quoted

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

Please can you rewrite this describing the problem that you're solving,
rather than a brief summary of some requirements?

Okay. I'll fix this in v13.

quoted

Signed-off-by: Chintan Pandya <redacted>
---
  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)) {

Just some stylistic stuff, but please can you rewrite this as:

	if (!pud_present(pud) || VM_WARN_ON(!pud_table(pud)))
		return 1;

similarly for the pmd/pte code above.

Okay. v13 will have this.

quoted

+		table = pud_page_vaddr(pud);
+		entry = table;

Could you rename entry -> pmdp, please?

Sure.

quoted

+		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;

So with these patches, we only ever return 1 from these helpers. It looks
like the same is true for x86, so how about we make them void and move the
calls inside the conditionals in lib/ioremap.c? Obviously, this would be a
separate patch on the end.

That sounds valid code churn to me. But since x86 discussion is not
concluded yet, I would wait to share until that gets resolved. May be
not in v13 but separate effort. Would that be okay to you ?

Will

Chintan
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