[tip:x86/urgent] x86/mm: Expand static page table for fixmap space
From: tip-bot for Feng Tang
Date: Tue Sep 18 2018 - 18:13:44 EST
Commit-ID: 31217900acbaf66249b8befd06c975aa897b4deb
Gitweb: https://git.kernel.org/tip/31217900acbaf66249b8befd06c975aa897b4deb
Author: Feng Tang <feng.tang@xxxxxxxxx>
AuthorDate: Mon, 17 Sep 2018 17:14:23 +0800
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 19 Sep 2018 00:09:10 +0200
x86/mm: Expand static page table for fixmap space
We met a kernel panic when enabling earlycon, which is due to the fixmap
address of earlycon is not statically setup.
Currently the static fixmap setup in head_64.S only covers 2M virtual
address space, while it acutually could be in 4M space with different
kernel configurations.
So increase the static space to 4M for now by defining FIXMAP_PMD_NUM to 2,
and add a build time check to ensure that the fixmap is covered by the
intial static page tables.
[ tglx: s/PTRS_PER_PMD/PTRS_PER_PTE/ and add the missing brackets ]
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx> (Xen parts)
Cc: H Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20180917091423.16069-1-feng.tang@xxxxxxxxx
---
arch/x86/include/asm/fixmap.h | 8 ++++++++
arch/x86/include/asm/pgtable_64.h | 3 ++-
arch/x86/kernel/head_64.S | 16 ++++++++++++----
arch/x86/mm/pgtable.c | 9 +++++++++
arch/x86/xen/mmu_pv.c | 8 ++++++--
5 files changed, 37 insertions(+), 7 deletions(-)
diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
index e203169931c7..01e8da740293 100644
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -14,6 +14,14 @@
#ifndef _ASM_X86_FIXMAP_H
#define _ASM_X86_FIXMAP_H
+/*
+ * Exposed to assembly code for setting up initial page tables. Cannot be
+ * calculated in assembly code (fixmap entries are an enum), but is sanity
+ * checked in the actual fixmap C code to make sure that the fixmap is
+ * covered fully.
+ */
+#define FIXMAP_PMD_NUM 2
+
#ifndef __ASSEMBLY__
#include <linux/kernel.h>
#include <asm/acpi.h>
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index ce2b59047cb8..9c85b54bf03c 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -14,6 +14,7 @@
#include <asm/processor.h>
#include <linux/bitops.h>
#include <linux/threads.h>
+#include <asm/fixmap.h>
extern p4d_t level4_kernel_pgt[512];
extern p4d_t level4_ident_pgt[512];
@@ -22,7 +23,7 @@ extern pud_t level3_ident_pgt[512];
extern pmd_t level2_kernel_pgt[512];
extern pmd_t level2_fixmap_pgt[512];
extern pmd_t level2_ident_pgt[512];
-extern pte_t level1_fixmap_pgt[512];
+extern pte_t level1_fixmap_pgt[512 * FIXMAP_PMD_NUM];
extern pgd_t init_top_pgt[];
#define swapper_pg_dir init_top_pgt
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 15ebc2fc166e..a3618cf04cf6 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -24,6 +24,7 @@
#include "../entry/calling.h"
#include <asm/export.h>
#include <asm/nospec-branch.h>
+#include <asm/fixmap.h>
#ifdef CONFIG_PARAVIRT
#include <asm/asm-offsets.h>
@@ -445,13 +446,20 @@ NEXT_PAGE(level2_kernel_pgt)
KERNEL_IMAGE_SIZE/PMD_SIZE)
NEXT_PAGE(level2_fixmap_pgt)
- .fill 506,8,0
- .quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
- /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
- .fill 5,8,0
+ .fill (512 - 4 - FIXMAP_PMD_NUM),8,0
+ pgtno = 0
+ .rept (FIXMAP_PMD_NUM)
+ .quad level1_fixmap_pgt + (pgtno << PAGE_SHIFT) - __START_KERNEL_map \
+ + _PAGE_TABLE_NOENC;
+ pgtno = pgtno + 1
+ .endr
+ /* 6 MB reserved space + a 2MB hole */
+ .fill 4,8,0
NEXT_PAGE(level1_fixmap_pgt)
+ .rept (FIXMAP_PMD_NUM)
.fill 512,8,0
+ .endr
#undef PMDS
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index ae394552fb94..089e78c4effd 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -637,6 +637,15 @@ void __native_set_fixmap(enum fixed_addresses idx, pte_t pte)
{
unsigned long address = __fix_to_virt(idx);
+#ifdef CONFIG_X86_64
+ /*
+ * Ensure that the static initial page tables are covering the
+ * fixmap completely.
+ */
+ BUILD_BUG_ON(__end_of_permanent_fixed_addresses >
+ (FIXMAP_PMD_NUM * PTRS_PER_PTE));
+#endif
+
if (idx >= __end_of_fixed_addresses) {
BUG();
return;
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 2fe5c9b1816b..dd461c0167ef 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1907,7 +1907,7 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
/* L3_k[511] -> level2_fixmap_pgt */
convert_pfn_mfn(level3_kernel_pgt);
- /* L3_k[511][506] -> level1_fixmap_pgt */
+ /* L3_k[511][508-FIXMAP_PMD_NUM ... 507] -> level1_fixmap_pgt */
convert_pfn_mfn(level2_fixmap_pgt);
/* We get [511][511] and have Xen's version of level2_kernel_pgt */
@@ -1952,7 +1952,11 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
set_page_prot(level2_ident_pgt, PAGE_KERNEL_RO);
set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
- set_page_prot(level1_fixmap_pgt, PAGE_KERNEL_RO);
+
+ for (i = 0; i < FIXMAP_PMD_NUM; i++) {
+ set_page_prot(level1_fixmap_pgt + i * PTRS_PER_PTE,
+ PAGE_KERNEL_RO);
+ }
/* Pin down new L4 */
pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,