This is a note to let you know that I've just added the patch titled
x86/boot/compressed/64: Detect and handle 5-level paging at boot-time
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: x86-boot-compressed-64-detect-and-handle-5-level-paging-at-boot-time.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 08529078d8d9adf689bf39cc38d53979a0869970 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Date: Mon, 4 Dec 2017 15:40:55 +0300 Subject: x86/boot/compressed/64: Detect and handle 5-level paging at boot-time
From: Kirill A. Shutemov kirill.shutemov@linux.intel.com
commit 08529078d8d9adf689bf39cc38d53979a0869970 upstream.
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: 77ef56e4f0fb ("x86: Enable 5-level paging support via CONFIG_X86_5LEVEL=y") Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: Andi Kleen ak@linux.intel.com 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... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/boot/compressed/Makefile | 1 + arch/x86/boot/compressed/head_64.S | 16 ++++++++++++---- arch/x86/boot/compressed/pgtable_64.c | 28 ++++++++++++++++++++++++++++ 3 files changed, 41 insertions(+), 4 deletions(-)
--- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -78,6 +78,7 @@ vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $ vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o ifdef CONFIG_X86_64 vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/pagetable.o + vmlinux-objs-y += $(obj)/pgtable_64.o endif
$(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -289,10 +289,18 @@ 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, --- /dev/null +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -0,0 +1,28 @@ +#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; +}
Patches currently in stable-queue which might be from kirill.shutemov@linux.intel.com are
queue-4.14/x86-boot-compressed-64-print-error-if-5-level-paging-is-not-supported.patch queue-4.14/x86-boot-compressed-64-detect-and-handle-5-level-paging-at-boot-time.patch