path: root/arch
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authorWanpeng Li <wanpeng.li@hotmail.com>2017-08-01 05:20:03 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-08-11 09:08:47 -0700
commitbbccdb1e442be9b705564479d8b0c55b9b202dad (patch)
tree9adb72ae59275a5d16326cbc7eda0f23147247c3 /arch
parent7de8d0c06e566c8c2625577fc9edea2ddd0ca16f (diff)
KVM: async_pf: make rcu irq exit if not triggered from idle task
commit 337c017ccdf2653d0040099433fc1a2b1beb5926 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 9b132fbe5419 (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: Wanpeng Li <wanpeng.li@hotmail.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index cec49ecf5f31..32187f8a49b4 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -151,6 +151,8 @@ void kvm_async_pf_task_wait(u32 token)
if (hlist_unhashed(&n.link))
+ rcu_irq_exit();
if (!n.halted) {
@@ -159,11 +161,11 @@ void kvm_async_pf_task_wait(u32 token)
* We cannot reschedule. So halt.
- rcu_irq_exit();
- rcu_irq_enter();
+ rcu_irq_enter();
if (!n.halted)
finish_wait(&n.wq, &wait);