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Message-Id: <20180917073449.20693-1-feng.tang@intel.com>
Date: Mon, 17 Sep 2018 15:34:49 +0800
From: Feng Tang <feng.tang@...el.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
H Peter Anvin <hpa@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Michal Hocko <mhocko@...nel.org>, x86@...nel.org,
linux-kernel@...r.kernel.org, Yinghai Lu <yinghai@...nel.org>,
Dave Hansen <dave.hansen@...el.com>,
Andi Kleen <ak@...ux.intel.com>
Cc: Feng Tang <feng.tang@...el.com>
Subject: [PATCH] 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 for future possible overflow so that
the macro could be increased accordingly.
Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Feng Tang <feng.tang@...el.com>
---
arch/x86/include/asm/fixmap.h | 3 +++
arch/x86/include/asm/pgtable_64.h | 3 ++-
arch/x86/kernel/head_64.S | 16 ++++++++++++----
arch/x86/mm/pgtable.c | 10 ++++++++++
arch/x86/xen/mmu_pv.c | 4 +++-
5 files changed, 30 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h
index e203169..ffaa0fa 100644
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -14,6 +14,9 @@
#ifndef _ASM_X86_FIXMAP_H
#define _ASM_X86_FIXMAP_H
+/* Put here to be accessble for assembly code like head_64.S */
+#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 ce2b590..9c85b54 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 15ebc2f..a3618cf 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 ae39455..a4052b1 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -637,6 +637,16 @@ void __native_set_fixmap(enum fixed_addresses idx, pte_t pte)
{
unsigned long address = __fix_to_virt(idx);
+#ifdef CONFIG_X86_64
+ /*
+ * In arch/x86/kernel/head_64.S, the static page table has
+ * been setup for fixmap. Add a sanity compiling check
+ * whether fixmap space has exceeded the capacity.
+ */
+ BUILD_BUG_ON(__end_of_permanent_fixed_addresses
+ > (FIXMAP_PMD_NUM * PTRS_PER_PMD));
+#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 2fe5c9b..19077f9 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1952,7 +1952,9 @@ 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 * 512, PAGE_KERNEL_RO);
/* Pin down new L4 */
pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,
--
2.7.4
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