[PATCH 0/2] x86/mm: Fix 'no5lvl' handling in v4.18-rc1

[PATCH 0/2] x86/mm: Fix 'no5lvl' handling in v4.18-rc1

[Kirill A. Shutemov]

One of patches from 'no5lvl' patchset didn't get merged due collision with
other code and I screwed up bisectablity. As result 'no5lvl' is broken in
v4.18-rc1.

Fix the mess.

Kirill A. Shutemov (2):
  Revert "x86/mm: Mark __pgtable_l5_enabled __initdata"
  x86/mm: Fix 'no5lvl' handling

 arch/x86/kernel/cpu/common.c | 3 +++
 arch/x86/kernel/head64.c     | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

-- 
2.17.1

[PATCH 1/2] Revert "x86/mm: Mark __pgtable_l5_enabled __initdata"

[Kirill A. Shutemov]

This reverts commit e4e961e36f063484c48bed919013c106d178995d.

We need to use early version of pgtable_l5_enabled() in
early_identify_cpu() as this code runs before cpu_feature_enabled() is
usable.

But it leads to section mismatch:

cpu_init()
  load_mm_ldt()
    ldt_slot_va()
      LDT_BASE_ADDR
        LDT_PGD_ENTRY
	  pgtable_l5_enabled()
	    __pgtable_l5_enabled

__pgtable_l5_enabled marked as __initdata, but cpu_init() is not __init.

It's fixable: early code can be isolated into a separate translation
unit, but such change collides with other work in the area.
That's too much hassle to save 4 bytes of memory.

Return __pgtable_l5_enabled back to be __ro_after_init.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/kernel/head64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index a21d6ace648e..8047379e575a 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -44,7 +44,7 @@ static unsigned int __initdata next_early_pgt;
 pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
 
 #ifdef CONFIG_X86_5LEVEL
-unsigned int __pgtable_l5_enabled __initdata;
+unsigned int __pgtable_l5_enabled __ro_after_init;
 unsigned int pgdir_shift __ro_after_init = 39;
 EXPORT_SYMBOL(pgdir_shift);
 unsigned int ptrs_per_p4d __ro_after_init = 1;
-- 
2.17.1

[tip:x86/urgent] Revert "x86/mm: Mark __pgtable_l5_enabled __initdata"

[tip-bot for Kirill A. Shutemov]

Commit-ID:  51be1335151771075dcb19f3464ca9f331134285
Gitweb:     https://git.kernel.org/tip/51be1335151771075dcb19f3464ca9f331134285
Author:     Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
AuthorDate: Sat, 23 Jun 2018 01:08:40 +0300
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sat, 23 Jun 2018 14:20:37 +0200

Revert "x86/mm: Mark __pgtable_l5_enabled __initdata"

This reverts commit e4e961e36f063484c48bed919013c106d178995d.

We need to use early version of pgtable_l5_enabled() in
early_identify_cpu() as this code runs before cpu_feature_enabled() is
usable.

But it leads to section mismatch:

cpu_init()
  load_mm_ldt()
    ldt_slot_va()
      LDT_BASE_ADDR
        LDT_PGD_ENTRY
	  pgtable_l5_enabled()
	    __pgtable_l5_enabled

__pgtable_l5_enabled marked as __initdata, but cpu_init() is not __init.

It's fixable: early code can be isolated into a separate translation unit,
but such change collides with other work in the area.  That's too much
hassle to save 4 bytes of memory.

Return __pgtable_l5_enabled back to be __ro_after_init.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20180622220841.54135-2-kirill.shutemov@linux.intel.com

---
 arch/x86/kernel/head64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index a21d6ace648e..8047379e575a 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -44,7 +44,7 @@ static unsigned int __initdata next_early_pgt;
 pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
 
 #ifdef CONFIG_X86_5LEVEL
-unsigned int __pgtable_l5_enabled __initdata;
+unsigned int __pgtable_l5_enabled __ro_after_init;
 unsigned int pgdir_shift __ro_after_init = 39;
 EXPORT_SYMBOL(pgdir_shift);
 unsigned int ptrs_per_p4d __ro_after_init = 1;

[PATCH 2/2] x86/mm: Fix 'no5lvl' handling

[Kirill A. Shutemov]

early_identify_cpu() has to use early version of pgtable_l5_enabled()
that doesn't rely on cpu_feature_enabled().

Defining USE_EARLY_PGTABLE_L5 before all includes does the trick.

I lost the define in one of reworks of the original patch.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Fixes: 372fddf70904 ("x86/mm: Introduce the 'no5lvl' kernel parameter")
---
 arch/x86/kernel/cpu/common.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 0df7151cfef4..eb4cb3efd20e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1,3 +1,6 @@
+/* cpu_feature_enabled() cannot be used this early */
+#define USE_EARLY_PGTABLE_L5
+
 #include <linux/bootmem.h>
 #include <linux/linkage.h>
 #include <linux/bitops.h>
-- 
2.17.1

[tip:x86/urgent] x86/mm: Fix 'no5lvl' handling

[tip-bot for Kirill A. Shutemov]

Commit-ID:  2458e53ff74cd1063ed3e00459da1d35c559d369
Gitweb:     https://git.kernel.org/tip/2458e53ff74cd1063ed3e00459da1d35c559d369
Author:     Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
AuthorDate: Sat, 23 Jun 2018 01:08:41 +0300
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sat, 23 Jun 2018 14:20:37 +0200

x86/mm: Fix 'no5lvl' handling

early_identify_cpu() has to use early version of pgtable_l5_enabled()
that doesn't rely on cpu_feature_enabled().

Defining USE_EARLY_PGTABLE_L5 before all includes does the trick.

I lost the define in one of reworks of the original patch.

Fixes: 372fddf70904 ("x86/mm: Introduce the 'no5lvl' kernel parameter")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20180622220841.54135-3-kirill.shutemov@linux.intel.com

---
 arch/x86/kernel/cpu/common.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 0df7151cfef4..eb4cb3efd20e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1,3 +1,6 @@
+/* cpu_feature_enabled() cannot be used this early */
+#define USE_EARLY_PGTABLE_L5
+
 #include <linux/bootmem.h>
 #include <linux/linkage.h>
 #include <linux/bitops.h>