4.14-stable review patch. If anyone has any objections, please let me know.
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From: Zhenzhong Duan zhenzhong.duan@oracle.com
[ Upstream commit 4fb5f58e8d191f7c81637ad81284e4848afb4244 ]
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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/smpboot.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -223,6 +223,11 @@ static void notrace start_secondary(void #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();