path: root/arch/x86/kernel/setup_percpu.c
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authorAndy Lutomirski <luto@kernel.org>2017-03-22 14:32:32 -0700
committerIngo Molnar <mingo@kernel.org>2017-03-23 08:25:08 +0100
commit23b2a4ddebdd17fad265b4bb77256c2e4ec37dee (patch)
tree85f136c21db6fad958224eca963c5ad45a8083ad /arch/x86/kernel/setup_percpu.c
parent3fa1cabbc3b61224ef33d3ca4a1a96998529bc68 (diff)
x86/boot/32: Defer resyncing initial_page_table until per-cpu is set up
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>
Diffstat (limited to 'arch/x86/kernel/setup_percpu.c')
1 files changed, 21 insertions, 0 deletions
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 11338b0b3ad2..bb1e8cc0bc84 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -288,4 +288,25 @@ void __init setup_per_cpu_areas(void)
/* Setup cpu initialized, callin, callout 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,
+ /*
+ * 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,