From: "Kirill A. Shutemov" Date: Mon, 4 Dec 2017 15:40:56 +0300 Subject: x86/boot/compressed/64: Print error if 5-level paging is not supported Git-commit: 6d7e0ba2d2be9e50cccba213baf07e0e183c1b24 Patch-mainline: v4.15-rc4 References: bsc#1110006 If the machine does not support the paging mode for which the kernel was compiled, the boot process cannot continue. It's not possible to let the kernel detect the mismatch as it does not even reach the point where cpu features can be evaluted due to a triple fault in the KASLR setup. Instead of instantaneous silent reboot, emit an error message which gives the user the information why the boot fails. Fixes: 77ef56e4f0fb ("x86: Enable 5-level paging support via CONFIG_X86_5LEVEL=y") Reported-by: Borislav Petkov Signed-off-by: Kirill A. Shutemov Signed-off-by: Thomas Gleixner Tested-by: Borislav Petkov Cc: Andi Kleen Cc: stable@vger.kernel.org Cc: Andy Lutomirski Cc: linux-mm@kvack.org Cc: Cyrill Gorcunov Cc: Linus Torvalds Link: https://lkml.kernel.org/r/20171204124059.63515-3-kirill.shutemov@linux.intel.com Acked-by: Joerg Roedel --- arch/x86/boot/compressed/misc.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index b50c42455e25..98761a1576ce 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -169,6 +169,16 @@ void __puthex(unsigned long value) } } +static bool l5_supported(void) +{ + /* Check if leaf 7 is supported. */ + if (native_cpuid_eax(0) < 7) + return 0; + + /* Check if la57 is supported. */ + return native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31)); +} + #if CONFIG_X86_NEED_RELOCS static void handle_relocations(void *output, unsigned long output_len, unsigned long virt_addr) @@ -362,6 +372,12 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, console_init(); debug_putstr("early console in extract_kernel\n"); + if (IS_ENABLED(CONFIG_X86_5LEVEL) && !l5_supported()) { + error("This linux kernel as configured requires 5-level paging\n" + "This CPU does not support the required 'cr4.la57' feature\n" + "Unable to boot - please use a kernel appropriate for your CPU\n"); + } + free_mem_ptr = heap; /* Heap */ free_mem_end_ptr = heap + BOOT_HEAP_SIZE;