From 08529078d8d9adf689bf39cc38d53979a0869970 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Mon, 4 Dec 2017 15:40:55 +0300 Subject: [PATCH] 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: 77ef56e4f0fb ("x86: Enable 5-level paging support via CONFIG_X86_5LEVEL=y") Signed-off-by: Kirill A. Shutemov Signed-off-by: Thomas Gleixner Cc: Andi Kleen Cc: stable@vger.kernel.org Cc: Andy Lutomirski Cc: linux-mm@kvack.org Cc: Cyrill Gorcunov Cc: Borislav Petkov Cc: Linus Torvalds Link: https://lkml.kernel.org/r/20171204124059.63515-2-kirill.shutemov@linux.intel.com --- 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(-) create mode 100644 arch/x86/boot/compressed/pgtable_64.c diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 1e9c322e973a..f25e1530e064 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -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 diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 20919b4f3133..fc313e29fe2c 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -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, diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c new file mode 100644 index 000000000000..b4469a37e9a1 --- /dev/null +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -0,0 +1,28 @@ +#include + +/* + * __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; +} -- 2.45.2