lkml.org 
[lkml]   [2018]   [Oct]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 1/3] x86/mm/pat: Disable preemption around __flush_tlb_all()
    Date
    I've seen the WARN_ON_ONCE(__read_cr3() != build_cr3()) in
    switch_mm_irqs_off() every once in a while during a snapshotted system
    upgrade.
    I also saw the warning early during which was introduced in 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.

    Turns out, once I disable preemption around __flush_tlb_all() both
    warnings do not appear.

    Disable preemption during CR3 reset / __flush_tlb_all().

    Fixes: decab0888e6e ("x86/mm: Remove preempt_disable/enable() from __native_flush_tlb()")
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    ---
    arch/x86/mm/pageattr.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
    index 51a5a69ecac9f..fe6b21f0a6631 100644
    --- a/arch/x86/mm/pageattr.c
    +++ b/arch/x86/mm/pageattr.c
    @@ -2088,7 +2088,9 @@ 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:
    */
    + preempt_disable();
    __flush_tlb_all();
    + preempt_enable();

    arch_flush_lazy_mmu_mode();
    }
    --
    2.19.1
    \
     
     \ /
      Last update: 2018-10-16 22:26    [W:4.603 / U:0.152 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site