This is a note to let you know that I've just added the patch titled
x86/pti/efi: broken conversion from efi to kernel page table
to the 4.9-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-pti-efi-broken-conversion-from-efi-to-kernel-page-table.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From pasha.tatashin@xxxxxxxxxx Sat Jan 13 14:16:28 2018
From: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Date: Thu, 11 Jan 2018 16:58:20 -0500
Subject: x86/pti/efi: broken conversion from efi to kernel page table
To: steven.sistare@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, tglx@xxxxxxxxxxxxx, mingo@xxxxxxxxxx, hpa@xxxxxxxxx, x86@xxxxxxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx, jkosina@xxxxxxx, hughd@xxxxxxxxxx, dave.hansen@xxxxxxxxxxxxxxx, luto@xxxxxxxxxx, torvalds@xxxxxxxxxxxxxxxxxxxx
Message-ID: <20180111215820.29736-1-pasha.tatashin@xxxxxxxxxx>
From: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
The page table order must be increased for EFI table in order to avoid a
bug where NMI tries to change the page table to kernel page table, while
efi page table is active.
For more disccussion about this bug, see this thread:
http://lkml.iu.edu/hypermail/linux/kernel/1801.1/00951.html
Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Reviewed-by: Steven Sistare <steven.sistare@xxxxxxxxxx>
Acked-by: Jiri Kosina <jkosina@xxxxxxx>
---
arch/x86/include/asm/pgalloc.h | 11 +++++++++++
arch/x86/platform/efi/efi_64.c | 2 +-
2 files changed, 12 insertions(+), 1 deletion(-)
--- a/arch/x86/include/asm/pgalloc.h
+++ b/arch/x86/include/asm/pgalloc.h
@@ -27,6 +27,17 @@ static inline void paravirt_release_pud(
*/
extern gfp_t __userpte_alloc_gfp;
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+/*
+ * Instead of one PGD, we acquire two PGDs. Being order-1, it is
+ * both 8k in size and 8k-aligned. That lets us just flip bit 12
+ * in a pointer to swap between the two 4k halves.
+ */
+#define PGD_ALLOCATION_ORDER 1
+#else
+#define PGD_ALLOCATION_ORDER 0
+#endif
+
/*
* Allocate and free page tables.
*/
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -142,7 +142,7 @@ int __init efi_alloc_page_tables(void)
return 0;
gfp_mask = GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO;
- efi_pgd = (pgd_t *)__get_free_page(gfp_mask);
+ efi_pgd = (pgd_t *)__get_free_pages(gfp_mask, PGD_ALLOCATION_ORDER);
if (!efi_pgd)
return -ENOMEM;
Patches currently in stable-queue which might be from pasha.tatashin@xxxxxxxxxx are
queue-4.9/x86-pti-efi-broken-conversion-from-efi-to-kernel-page-table.patch