linux-kernel - [PATCH 2/9] x86/mm: Initialize pgdir_shift and ptrs_per

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Date:   Wed, 14 Feb 2018 21:25:35 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...e.de>, Andi Kleen <ak@...ux.intel.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 2/9] x86/mm: Initialize pgdir_shift and ptrs_per_p4d at boot-time

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.shutemov@...ux.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