queue/x86-pti-efi-broken-conversion-from-efi-to-kernel-page-table.patch

From pasha.tatashin@oracle.com  Mon Jan 15 18:48:49 2018
From: Pavel Tatashin <pasha.tatashin@oracle.com>
Date: Mon, 15 Jan 2018 11:44:14 -0500
Subject: x86/pti/efi: broken conversion from efi to kernel page table
To: steven.sistare@oracle.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, gregkh@linuxfoundation.org, jkosina@suse.cz, hughd@google.com, dave.hansen@linux.intel.com, luto@kernel.org, stable@vger.kernel.org
Message-ID: <20180115164414.19778-1-pasha.tatashin@oracle.com>

From: Pavel Tatashin <pasha.tatashin@oracle.com>

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@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/include/asm/pgalloc.h |   11 +++++++++++
 arch/x86/mm/pgtable.c          |    7 -------
 arch/x86/platform/efi/efi_64.c |    2 +-
 3 files changed, 12 insertions(+), 8 deletions(-)

Changelog:
	v1 - v2: Fixed compiling warning

--- 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/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -345,13 +345,6 @@ static inline void _pgd_free(pgd_t *pgd)
 }
 #else
 
-/*
- * Instead of one pgd, Kaiser acquires 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	kaiser_enabled
-
 static inline pgd_t *_pgd_alloc(void)
 {
 	return (pgd_t *)__get_free_pages(PGALLOC_GFP, PGD_ALLOCATION_ORDER);
--- 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;