This is a note to let you know that I've just added the patch titled x86/mm/pat: Disable preemption around __flush_tlb_all() to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-mm-pat-disable-preemption-around-__flush_tlb_all.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From f77084d96355f5fba8e2c1fb3a51a393b1570de7 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Date: Wed, 17 Oct 2018 12:34:32 +0200 Subject: x86/mm/pat: Disable preemption around __flush_tlb_all() From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> commit f77084d96355f5fba8e2c1fb3a51a393b1570de7 upstream. The WARN_ON_ONCE(__read_cr3() != build_cr3()) in switch_mm_irqs_off() triggers every once in a while during a snapshotted system upgrade. The warning triggers since commit decab0888e6e ("x86/mm: Remove preempt_disable/enable() from __native_flush_tlb()"). The callchain is: get_page_from_freelist() -> post_alloc_hook() -> __kernel_map_pages() with CONFIG_DEBUG_PAGEALLOC enabled. Disable preemption during CR3 reset / __flush_tlb_all() and add a comment why preemption has to be disabled so it won't be removed accidentaly. Add another preemptible() check in __flush_tlb_all() to catch callers with enabled preemption when PGE is enabled, because PGE enabled does not trigger the warning in __native_flush_tlb(). Suggested by Andy Lutomirski. Fixes: decab0888e6e ("x86/mm: Remove preempt_disable/enable() from __native_flush_tlb()") Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20181017103432.zgv46nlu3hc7k4rq@xxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/include/asm/tlbflush.h | 6 ++++++ arch/x86/mm/pageattr.c | 6 +++++- 2 files changed, 11 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -466,6 +466,12 @@ static inline void __native_flush_tlb_on */ static inline void __flush_tlb_all(void) { + /* + * This is to catch users with enabled preemption and the PGE feature + * and don't trigger the warning in __native_flush_tlb(). + */ + VM_WARN_ON_ONCE(preemptible()); + if (boot_cpu_has(X86_FEATURE_PGE)) { __flush_tlb_global(); } else { --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -2037,9 +2037,13 @@ void __kernel_map_pages(struct page *pag /* * We should perform an IPI and flush all tlbs, - * but that can deadlock->flush only current cpu: + * but that can deadlock->flush only current cpu. + * Preemption needs to be disabled around __flush_tlb_all() due to + * CR3 reload in __native_flush_tlb(). */ + preempt_disable(); __flush_tlb_all(); + preempt_enable(); arch_flush_lazy_mmu_mode(); } Patches currently in stable-queue which might be from bigeasy@xxxxxxxxxxxxx are queue-4.14/x86-mm-pat-disable-preemption-around-__flush_tlb_all.patch