linux-kernel - [PATCH 2/2] x86/mm: implement free pmd/pte page interfaces

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Date:   Wed,  7 Mar 2018 11:32:27 -0700
From:   Toshi Kani <toshi.kani@....com>
To:     mhocko@...e.com, akpm@...ux-foundation.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, bp@...e.de,
        catalin.marinas@....com
Cc:     guohanjun@...wei.com, will.deacon@....com, wxf.wang@...ilicon.com,
        linux-mm@...ck.org, x86@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Toshi Kani <toshi.kani@....com>
Subject: [PATCH 2/2] x86/mm: implement free pmd/pte page interfaces

Implement pud_free_pmd_page() and pmd_free_pte_page() on x86, which
clear a given pud/pmd entry and free up lower level page table(s).
Address range associated with the pud/pmd entry must have been purged
by INVLPG.

Signed-off-by: Toshi Kani <toshi.kani@....com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Borislav Petkov <bp@...e.de>
---
 arch/x86/mm/pgtable.c |   28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 942f4fa341f1..121c0114439e 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -710,7 +710,22 @@ int pmd_clear_huge(pmd_t *pmd)
  */
 int pud_free_pmd_page(pud_t *pud)
 {
-	return pud_none(*pud);
+	pmd_t *pmd;
+	int i;
+
+	if (pud_none(*pud))
+		return 1;
+
+	pmd = (pmd_t *)pud_page_vaddr(*pud);
+
+	for (i = 0; i < PTRS_PER_PMD; i++)
+		if (!pmd_free_pte_page(&pmd[i]))
+			return 0;
+
+	pud_clear(pud);
+	free_page((unsigned long)pmd);
+
+	return 1;
 }
 
 /**
@@ -720,6 +735,15 @@ int pud_free_pmd_page(pud_t *pud)
  */
 int pmd_free_pte_page(pmd_t *pmd)
 {
-	return pmd_none(*pmd);
+	pte_t *pte;
+
+	if (pmd_none(*pmd))
+		return 1;
+
+	pte = (pte_t *)pmd_page_vaddr(*pmd);
+	pmd_clear(pmd);
+	free_page((unsigned long)pte);
+
+	return 1;
 }
 #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */