Commit 4fb5f58e authored Jul 02, 2018 by Zhenzhong Duan Committed by Ingo Molnar Jul 03, 2018

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 <zhenzhong.duan@oracle.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: http://lkml.kernel.org/r/b07b6ae9-4b57-4b40-b9bc-50c2c67f1d91@default


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 021c9179

arch/x86/kernel/smpboot.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -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();