• Wanpeng Li's avatar
    KVM: async_pf: make rcu irq exit if not triggered from idle task · bbccdb1e
    Wanpeng Li authored
    commit 337c017c upstream.
    
     WARNING: CPU: 5 PID: 1242 at kernel/rcu/tree_plugin.h:323 rcu_note_context_switch+0x207/0x6b0
     CPU: 5 PID: 1242 Comm: unity-settings- Not tainted 4.13.0-rc2+ #1
     RIP: 0010:rcu_note_context_switch+0x207/0x6b0
     Call Trace:
      __schedule+0xda/0xba0
      ? kvm_async_pf_task_wait+0x1b2/0x270
      schedule+0x40/0x90
      kvm_async_pf_task_wait+0x1cc/0x270
      ? prepare_to_swait+0x22/0x70
      do_async_page_fault+0x77/0xb0
      ? do_async_page_fault+0x77/0xb0
      async_page_fault+0x28/0x30
     RIP: 0010:__d_lookup_rcu+0x90/0x1e0
    
    I encounter this when trying to stress the async page fault in L1 guest w/
    L2 guests running.
    
    Commit 9b132fbe (Add rcu user eqs exception hooks for async page
    fault) adds rcu_irq_enter/exit() to kvm_async_pf_task_wait() to exit cpu
    idle eqs when needed, to protect the code that needs use rcu.  However,
    we need to call the pair even if the function calls schedule(), as seen
    from the above backtrace.
    
    This patch fixes it by informing the RCU subsystem exit/enter the irq
    towards/away from idle for both n.halted and !n.halted.
    
    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Cc: Radim Krčmář <rkrcmar@redhat.com>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Signed-off-by: default avatarWanpeng Li <wanpeng.li@hotmail.com>
    Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    bbccdb1e
kvm.c 19.9 KB