Commit 08529078 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Thomas Gleixner
Browse files

x86/boot/compressed/64: Detect and handle 5-level paging at boot-time 



Prerequisite for fixing the current problem of instantaneous reboots when a
5-level paging kernel is booted on 4-level paging hardware.

At the same time this change prepares the decompression code to boot-time
switching between 4- and 5-level paging.

[ tglx: Folded the GCC < 5 fix. ]

Fixes: 77ef56e4 ("x86: Enable 5-level paging support via CONFIG_X86_5LEVEL=y")
Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: stable@vger.kernel.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: linux-mm@kvack.org
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20171204124059.63515-2-kirill.shutemov@linux.intel.com
parent 947134d9

arch/x86/boot/compressed/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -80,6 +80,7 @@ vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o 
ifdef CONFIG_X86_64

	vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/pagetable.o

	vmlinux-objs-y += $(obj)/mem_encrypt.o

	vmlinux-objs-y += $(obj)/pgtable_64.o

endif



$(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone

arch/x86/boot/compressed/head_64.S

+12 −4
Original line number Diff line number Diff line
@@ -305,10 +305,18 @@ ENTRY(startup_64) 
	leaq	boot_stack_end(%rbx), %rsp



#ifdef CONFIG_X86_5LEVEL

	/* Check if 5-level paging has already enabled */

	movq	%cr4, %rax

	testl	$X86_CR4_LA57, %eax

	jnz	lvl5

	/*

	 * Check if we need to enable 5-level paging.

	 * RSI holds real mode data and need to be preserved across

	 * a function call.

	 */

	pushq	%rsi

	call	l5_paging_required

	popq	%rsi



	/* If l5_paging_required() returned zero, we're done here. */

	cmpq	$0, %rax

	je	lvl5



	/*

	 * At this point we are in long mode with 4-level paging enabled,

arch/x86/boot/compressed/pgtable_64.c

0 → 100644
+28 −0
Original line number Diff line number Diff line 
#include <asm/processor.h>



/*

 * __force_order is used by special_insns.h asm code to force instruction

 * serialization.

 *

 * It is not referenced from the code, but GCC < 5 with -fPIE would fail

 * due to an undefined symbol. Define it to make these ancient GCCs work.

 */

unsigned long __force_order;



int l5_paging_required(void)

{

	/* Check if leaf 7 is supported. */



	if (native_cpuid_eax(0) < 7)

		return 0;



	/* Check if la57 is supported. */

	if (!(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31))))

		return 0;



	/* Check if 5-level paging has already been enabled. */

	if (native_read_cr4() & X86_CR4_LA57)

		return 0;



	return 1;

}

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