* [PATCH v2] x86/mm: Expand static page table for fixmap space
@ 2018-09-17 8:39 Feng Tang
2018-09-17 8:49 ` Juergen Gross
0 siblings, 1 reply; 2+ messages in thread
From: Feng Tang @ 2018-09-17 8:39 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, H Peter Anvin, Peter Zijlstra,
Michal Hocko, x86, linux-kernel, Yinghai Lu, Dave Hansen,
Andi Kleen, Juergen Gross
Cc: Feng Tang
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@linutronix.de>
Signed-off-by: Feng Tang <feng.tang@intel.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 | 7 +++++--
5 files changed, 32 insertions(+), 7 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..74c4e17 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[507, 508 - FIXMAP_PMD_NUM] -> level1_fixmap_pgt */
convert_pfn_mfn(level2_fixmap_pgt);
/* We get [511][511] and have Xen's version of level2_kernel_pgt */
@@ -1952,7 +1952,10 @@ 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,
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] x86/mm: Expand static page table for fixmap space
2018-09-17 8:39 [PATCH v2] x86/mm: Expand static page table for fixmap space Feng Tang
@ 2018-09-17 8:49 ` Juergen Gross
0 siblings, 0 replies; 2+ messages in thread
From: Juergen Gross @ 2018-09-17 8:49 UTC (permalink / raw)
To: Feng Tang, Thomas Gleixner, Ingo Molnar, H Peter Anvin,
Peter Zijlstra, Michal Hocko, x86, linux-kernel, Yinghai Lu,
Dave Hansen, Andi Kleen
On 17/09/18 10:39, Feng Tang wrote:
> 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@linutronix.de>
> Signed-off-by: Feng Tang <feng.tang@intel.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 | 7 +++++--
> 5 files changed, 32 insertions(+), 7 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..74c4e17 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[507, 508 - FIXMAP_PMD_NUM] -> level1_fixmap_pgt */
You messed up the comment. The [511] must not be dropped.
I would swap the "508 - FIXMAP_PMD_NUM" and "507" in order to start
with the lower index, and replace "," by "...":
+ /* L3_k[511][508-FIXMAP_PMD_NUM ... 507] -> level1_fixmap_pgt */
With that corrected you can have my:
Reviewed-by: Juergen Gross <jgross@suse.com> (Xen parts)
Juergen
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2018-09-17 8:49 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-09-17 8:39 [PATCH v2] x86/mm: Expand static page table for fixmap space Feng Tang
2018-09-17 8:49 ` Juergen Gross
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.