From 4fb5f58e8d191f7c81637ad81284e4848afb4244 Mon Sep 17 00:00:00 2001 From: Zhenzhong Duan Date: Mon, 2 Jul 2018 23:49:54 -0700 Subject: [PATCH] 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 Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: "H. Peter Anvin" Link: http://lkml.kernel.org/r/b07b6ae9-4b57-4b40-b9bc-50c2c67f1d91@default Signed-off-by: Ingo Molnar --- arch/x86/kernel/smpboot.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index c2f7d1d2a5c3..db9656e13ea0 100644 --- 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(); -- 2.11.0