x86/mm/32: Initialize the CR4 shadow before __flush_tlb_all()

On 32-bit kernels, __flush_tlb_all() may have read the CR4 shadow before the
initialization of CR4 shadow in cpu_init().

Fix it by adding an explicit cr4_init_shadow() call into start_secondary()
which is the first function called on non-boot SMP CPUs - ahead of the
__flush_tlb_all() call.

( This is somewhat of a layering violation, but start_secondary() does
  CR4 bootstrap in the PCID case anyway. )

Signed-off-by: Zhenzhong Duan <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Link: http://lkml.kernel.org/r/b07b6ae9-4b57-4b40-b9bc-50c2c67f1d91@default
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index c2f7d1d2a5c36fca041809b727bde36afb347c34..db9656e13ea0418dbf9e619f183bd2176e2d94d6 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -221,6 +221,11 @@ static void notrace start_secondary(void *unused)
 #ifdef CONFIG_X86_32
        /* switch away from the initial page table */
        load_cr3(swapper_pg_dir);
+       /*
+        * Initialize the CR4 shadow before doing anything that could
+        * try to read it.
+        */
+       cr4_init_shadow();
        __flush_tlb_all();
 #endif
        load_current_idt();