On Wed, Nov 29, 2017 at 05:48:51PM +0000, Borislav Petkov wrote: > On Wed, Nov 29, 2017 at 08:08:31PM +0300, Kirill A. Shutemov wrote: > > We're really early in the boot -- startup_64 in decompression code -- and > > I don't know a way print a message there. Is there a way? > > > > no_longmode handled by just hanging the machine. Is it enough for no_la57 > > case too? > > Patch pls.
The patch below on top of patch 2/4 from this patch would do the trick. Please give it a shot. >From 95b5489d1f4ea03c6226d13eb6797825234489d6 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <[email protected]> Date: Thu, 30 Nov 2017 10:23:53 +0300 Subject: [PATCH] x86/boot/compressed/64: Print error if 5-level paging is not supported We cannot proceed booting if the machine doesn't support the paging mode kernel was compiled for. Getting error the usual way -- via validate_cpu() -- is not going to work. We need to enable appropriate paging mode before that, otherwise kernel would triple-fault during KASLR setup. This code will go away once we get support for boot-time switching between paging modes. Signed-off-by: Kirill A. Shutemov <[email protected]> --- arch/x86/boot/compressed/misc.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index b50c42455e25..5205e848dc33 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -40,6 +40,8 @@ /* Functions used by the included decompressor code below. */ void *memmove(void *dest, const void *src, size_t n); +int l5_paging_required(void); + /* * This is set up by the setup-routine at boot-time */ @@ -362,6 +364,13 @@ 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_paging_required()) { + error("The kernel is compiled with 5-level paging enabled, " + "but the CPU doesn't support la57\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; -- Kirill A. Shutemov
