This is a note to let you know that I've just added the patch titled
x86/mm: Disable ioremap free page handling on x86-PAE
to the 4.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-mm-disable-ioremap-free-page-handling-on-x86-pae.patch
and it can be found in the queue-4.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f967db0b9ed44ec3057a28f3b28efc51df51b835 Mon Sep 17 00:00:00 2001
From: Toshi Kani <toshi.kani@xxxxxxx>
Date: Wed, 27 Jun 2018 08:13:46 -0600
Subject: x86/mm: Disable ioremap free page handling on x86-PAE
From: Toshi Kani <toshi.kani@xxxxxxx>
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 <joro@xxxxxxxxxx>
Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: mhocko@xxxxxxxx
Cc: akpm@xxxxxxxxxxxxxxxxxxxx
Cc: hpa@xxxxxxxxx
Cc: cpandya@xxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20180627141348.21777-2-toshi.kani@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/pgtable.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -719,6 +719,7 @@ 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.
@@ -766,4 +767,22 @@ 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 */
Patches currently in stable-queue which might be from toshi.kani@xxxxxxx are
queue-4.18/x86-mm-disable-ioremap-free-page-handling-on-x86-pae.patch
