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

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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.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2017-03-22 14:32:32 -07:00 • committed by Ingo Molnar
parent 3fa1cabbc3
commit 23b2a4ddeb
2 changed files with 21 additions and 15 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

15
arch/x86/kernel/setup.c
View file

@ -1226,21 +1226,6 @@ void __init setup_arch(char **cmdline_p)
kasan_init(); 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(); tboot_probe();
map_vsyscall(); map_vsyscall();

21
arch/x86/kernel/setup_percpu.c
View file

@ -288,4 +288,25 @@ void __init setup_per_cpu_areas(void)
/* Setup cpu initialized, callin, callout masks */ /* Setup cpu initialized, callin, callout masks */
setup_cpu_local_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
} }