This is a note to let you know that I've just added the patch titled

x86/boot/32: Defer resyncing initial_page_table until per-cpu is set up

to the 4.9-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-32-defer-resyncing-initial_page_table-until-per-cpu-is-set-up.patch and it can be found in the queue-4.9 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 foo@baz Sun Mar 18 16:55:33 CET 2018

From: Andy Lutomirski luto@kernel.org Date: Wed, 22 Mar 2017 14:32:32 -0700 Subject: x86/boot/32: Defer resyncing initial_page_table until per-cpu is set up

From: Andy Lutomirski luto@kernel.org

[ Upstream commit 23b2a4ddebdd17fad265b4bb77256c2e4ec37dee ]

The x86 smpboot trampoline expects initial_page_table to have the GDT mapped. If the GDT ends up in a virtually mapped per-cpu page, then it won't be in the page tables at all until perc-pu areas are set up. The result will be a triple fault the first time that the CPU attempts to access the GDT after LGDT loads the perc-pu GDT.

This appears to be an old bug, but somehow the GDT fixmap rework is triggering it. This seems to have something to do with the memory layout.

Signed-off-by: Andy Lutomirski luto@kernel.org Cc: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Borislav Petkov bp@alien8.de Cc: Brian Gerst brgerst@gmail.com Cc: Denys Vlasenko dvlasenk@redhat.com Cc: H. Peter Anvin hpa@zytor.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Juergen Gross jgross@suse.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Matt Fleming matt@codeblueprint.co.uk Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Garnier thgarnie@google.com Cc: Thomas Gleixner tglx@linutronix.de Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/a553264a5972c6a86f9b5caac237470a0c74a720.1490218061... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/setup.c | 15 --------------- arch/x86/kernel/setup_percpu.c | 21 +++++++++++++++++++++ 2 files changed, 21 insertions(+), 15 deletions(-)

--- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1200,21 +1200,6 @@ void __init setup_arch(char **cmdline_p)

kasan_init();

-#ifdef CONFIG_X86_32 - /* sync back kernel address range */ - clone_pgd_range(initial_page_table + KERNEL_PGD_BOUNDARY, - swapper_pg_dir + KERNEL_PGD_BOUNDARY, - KERNEL_PGD_PTRS); - - /* - * sync back low identity map too. It is used for example - * in the 32-bit EFI stub. - */ - clone_pgd_range(initial_page_table, - swapper_pg_dir + KERNEL_PGD_BOUNDARY, - min(KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY)); -#endif - tboot_probe();

map_vsyscall(); --- a/arch/x86/kernel/setup_percpu.c +++ b/arch/x86/kernel/setup_percpu.c @@ -287,4 +287,25 @@ void __init setup_per_cpu_areas(void)

/* Setup cpu initialized, callin, callout masks */ setup_cpu_local_masks(); + +#ifdef CONFIG_X86_32 + /* + * Sync back kernel address range. We want to make sure that + * all kernel mappings, including percpu mappings, are available + * in the smpboot asm. We can't reliably pick up percpu + * mappings using vmalloc_fault(), because exception dispatch + * needs percpu data. + */ + clone_pgd_range(initial_page_table + KERNEL_PGD_BOUNDARY, + swapper_pg_dir + KERNEL_PGD_BOUNDARY, + KERNEL_PGD_PTRS); + + /* + * sync back low identity map too. It is used for example + * in the 32-bit EFI stub. + */ + clone_pgd_range(initial_page_table, + swapper_pg_dir + KERNEL_PGD_BOUNDARY, + min(KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY)); +#endif }

Patches currently in stable-queue which might be from luto@kernel.org are

queue-4.9/perf-tools-make-perf_event__synthesize_mmap_events-scale.patch queue-4.9/x86-mm-make-mmap-map_32bit-work-correctly.patch queue-4.9/x86-boot-32-defer-resyncing-initial_page_table-until-per-cpu-is-set-up.patch