From f77084d96355f5fba8e2c1fb3a51a393b1570de7 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Wed, 17 Oct 2018 12:34:32 +0200 Subject: [PATCH] x86/mm/pat: Disable preemption around __flush_tlb_all() 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 Signed-off-by: Thomas Gleixner Cc: Andy Lutomirski Cc: Dave Hansen Cc: Peter Zijlstra Cc: Borislav Petkov Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181017103432.zgv46nlu3hc7k4rq@linutronix.de --- arch/x86/include/asm/tlbflush.h | 6 ++++++ arch/x86/mm/pageattr.c | 6 +++++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index 323a313947e0..d760611cfc35 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -453,6 +453,12 @@ static inline void __native_flush_tlb_one_user(unsigned long addr) */ 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 { diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 62bb30b4bd2a..a1004dec98ea 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -2309,9 +2309,13 @@ void __kernel_map_pages(struct page *page, int numpages, int enable) /* * 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(); }