On Wed, Jun 07, 2017 at 08:03:25PM +0300, Kirill A. Shutemov wrote:

On Wed, Jun 07, 2017 at 10:46:20AM -0400, jglisse@redhat.com wrote:

quoted

From: Jerome Glisse <redacted>

With commit af2cf278ef4f we no longer free pud so that we do not
have synchronize all pgd on hotremove/vfree. But the new 5 level
page table patchset reverted that for 4 level page table.

This patch restore af2cf278ef4f and disable free_pud() if we are
in the 4 level page table case thus avoiding BUG_ON() after hot-
remove.

af2cf278ef4f x86/mm/hotplug: Don't remove PGD entries in remove_pagetable()

Changed since v1:
  - make free_pud() conditional on the number of page table
    level
  - improved commit message

Signed-off-by: Jerome Glisse <redacted>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kirill A. Shutemov <redacted>
Cc: Logan Gunthorpe <logang@deltatee.com>

quoted

thus we now trigger a BUG_ON() l128 in sync_global_pgds()

This patch remove free_pud() like in af2cf278ef4f

---
 arch/x86/mm/init_64.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 95651dc..61028bc 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c

@@ -771,6 +771,16 @@ static void __meminit free_pmd_table(pmd_t *pmd_start, pud_t *pud)
 	spin_unlock(&init_mm.page_table_lock);
 }
 
+/*
+ * For 4 levels page table we do not want to free puds but for 5 levels
+ * we should free them. This code also need to change to adapt for boot
+ * time switching between 4 and 5 level.
+ */
+#if CONFIG_PGTABLE_LEVELS == 4
+static inline void free_pud_table(pud_t *pud_start, p4d_t *p4d)
+{
+}

Just "if (CONFIG_PGTABLE_LEVELS > 4)" before calling free_pud_table(), but
okay -- I'll rework it anyway for boot-time switching.

Err. "if (CONFIG_PGTABLE_LEVELS == 4)" obviously.

-- 
 Kirill A. Shutemov

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