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Subject[PATCH 4.9 211/241] x86/boot/32: Fix UP boot on Quark and possibly other platforms
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Lutomirski <luto@kernel.org>

commit d2b6dc61a8dd3c429609b993778cb54e75a5c5f0 upstream.

This partially reverts commit:

23b2a4ddebdd17f ("x86/boot/32: Defer resyncing initial_page_table until per-cpu is set up")

That commit had one definite bug and one potential bug. The
definite bug is that setup_per_cpu_areas() uses a differnet generic
implementation on UP kernels, so initial_page_table never got
resynced. This was fine for access to percpu data (it's in the
identity map on UP), but it breaks other users of
initial_page_table. The potential bug is that helpers like
efi_init() would be called before the tables were synced.

Avoid both problems by just syncing the page tables in setup_arch()
*and* setup_per_cpu_areas().

Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
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: 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
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kernel/setup.c | 15 +++++++++++++++
arch/x86/kernel/setup_percpu.c | 10 +++++-----
2 files changed, 20 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1200,6 +1200,21 @@ 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
@@ -290,11 +290,11 @@ void __init setup_per_cpu_areas(void)

#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.
+ * Sync back kernel address range again. We already did this in
+ * setup_arch(), but percpu data also needs to be 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,

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