ioremap() supports pmd mappings on x86-PAE. However, kernel's pmd
tables are not shared among processes on x86-PAE. Therefore, any
update to sync'd pmd entries need re-syncing. Freeing a pte page
also leads to a vmalloc fault and hits the BUG_ON in vmalloc_sync_one().
Disable free page handling on x86-PAE. pud_free_pmd_page() and
pmd_free_pte_page() simply return 0 if a given pud/pmd entry is present.
This assures that ioremap() does not update sync'd pmd entries at the
cost of falling back to pte mappings.
Fixes: 28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces")
Reported-by: Joerg Roedel <joro@xxxxxxxxxx>
Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
arch/x86/mm/pgtable.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index ffc8c13c50e4..3f7180bc5f52 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -715,6 +715,7 @@ int pmd_clear_huge(pmd_t *pmd)
return 0;
}
+#ifdef CONFIG_X86_64
/**
* pud_free_pmd_page - Clear pud entry and free pmd page.
* @pud: Pointer to a PUD.
@@ -762,4 +763,22 @@ int pmd_free_pte_page(pmd_t *pmd)
return 1;
}
+
+#else /* !CONFIG_X86_64 */
+
+int pud_free_pmd_page(pud_t *pud)
+{
+ return pud_none(*pud);
+}
+
+/*
+ * Disable free page handling on x86-PAE. This assures that ioremap()
+ * does not update sync'd pmd entries. See vmalloc_sync_one().
+ */
+int pmd_free_pte_page(pmd_t *pmd)
+{
+ return pmd_none(*pmd);
+}
+
+#endif /* CONFIG_X86_64 */
#endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */
