x86/boot/32: Fix UP boot on Quark and possibly other platforms

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>

2 files changed, 20 insertions, 5 deletions

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 603a1669a2ec..0b4d3c686b1e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1225,6 +1225,21 @@ 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();
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index bb1e8cc0bc84..10edd1e69a68 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -291,11 +291,11 @@ 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,