4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Toshi Kani <toshi.k...@hpe.com>
commit f967db0b9ed44ec3057a28f3b28efc51df51b835 upstream.
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 <j...@8bytes.org>
Signed-off-by: Toshi Kani <toshi.k...@hpe.com>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: mho...@suse.com
Cc: a...@linux-foundation.org
Cc: h...@zytor.com
Cc: cpan...@codeaurora.org
Cc: linux...@kvack.org
Cc: linux-arm-ker...@lists.infradead.org
Cc: sta...@vger.kernel.org
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Michal Hocko <mho...@suse.com>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: <sta...@vger.kernel.org>
Link: https://lkml.kernel.org/r/20180627141348.21777-2-toshi.k...@hpe.com
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/x86/mm/pgtable.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -653,6 +653,7 @@ 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.
@@ -700,4 +701,22 @@ 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 */
