4.18-stable review patch. If anyone has any objections, please let me know.
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From: Sebastian Andrzej Siewior bigeasy@linutronix.de
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@linutronix.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: Andy Lutomirski luto@kernel.org Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Peter Zijlstra peterz@infradead.org Cc: Borislav Petkov bp@alien8.de Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181017103432.zgv46nlu3hc7k4rq@linutronix.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 @@ -469,6 +469,12 @@ 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 @@ -2063,9 +2063,13 @@ 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(); }