[PATCH 2/9] x86/mm: Initialize pgdir_shift and ptrs_per_p4d at boot-time

[Kirill A. Shutemov]

Switching between paging modes requires folding p4d page table level.
It means we need to adjust pgdir_shift and ptrs_per_p4d during early
boot according to paging mode.

Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
---
 arch/x86/boot/compressed/kaslr.c | 6 ++++--
 arch/x86/kernel/head64.c         | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index d02a838c0ce4..66e42a098d70 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -48,8 +48,8 @@
 
 #ifdef CONFIG_X86_5LEVEL
 unsigned int pgtable_l5_enabled __ro_after_init;
-unsigned int pgdir_shift __ro_after_init = 48;
-unsigned int ptrs_per_p4d __ro_after_init = 512;
+unsigned int pgdir_shift __ro_after_init = 39;
+unsigned int ptrs_per_p4d __ro_after_init = 1;
 #endif
 
 extern unsigned long get_cmd_line_ptr(void);
@@ -732,6 +732,8 @@ void choose_random_location(unsigned long input,
 #ifdef CONFIG_X86_5LEVEL
        if (__read_cr4() & X86_CR4_LA57) {
                pgtable_l5_enabled = 1;
+               pgdir_shift = 48;
+               ptrs_per_p4d = 512;
        }
 #endif
 
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index ffb31c50d515..8a0a485524da 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -42,9 +42,9 @@ pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & 
~(_PAGE_GLOBAL | _PAGE_NX);
 #ifdef CONFIG_X86_5LEVEL
 unsigned int pgtable_l5_enabled __ro_after_init;
 EXPORT_SYMBOL(pgtable_l5_enabled);
-unsigned int pgdir_shift __ro_after_init = 48;
+unsigned int pgdir_shift __ro_after_init = 39;
 EXPORT_SYMBOL(pgdir_shift);
-unsigned int ptrs_per_p4d __ro_after_init = 512;
+unsigned int ptrs_per_p4d __ro_after_init = 1;
 EXPORT_SYMBOL(ptrs_per_p4d);
 #endif
 
@@ -79,6 +79,8 @@ static void __head check_la57_support(unsigned long physaddr)
                return;
 
        *fixup_int(&pgtable_l5_enabled, physaddr) = 1;
+       *fixup_int(&pgdir_shift, physaddr) = 48;
+       *fixup_int(&ptrs_per_p4d, physaddr) = 512;
 }
 #else
 static void __head check_la57_support(unsigned long physaddr) {}
-- 
2.15.1