On Tue, 25 Jul 2017 09:43:15 +0200, Wanpeng Li wrote: > > From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > > Preempt can occur in the preemption timer expiration handler: > > CPU0 CPU1 > > preemption timer vmexit > handle_preemption_timer(vCPU0) > kvm_lapic_expired_hv_timer > hv_timer_is_use == true > sched_out > sched_in > kvm_arch_vcpu_load > kvm_lapic_restart_hv_timer > restart_apic_timer > start_hv_timer > already-expired timer or sw timer triggerd in the window > start_sw_timer > cancel_hv_timer > /* back in kvm_lapic_expired_hv_timer */ > cancel_hv_timer > WARN_ON(!apic->lapic_timer.hv_timer_in_use); ==> Oops > > This can be reproduced if CONFIG_PREEMPT is enabled. > > ------------[ cut here ]------------ > WARNING: CPU: 4 PID: 2972 at /home/kernel/linux/arch/x86/kvm//lapic.c:1563 kvm_lapic_expired_hv_timer+0x9e/0xb0 [kvm] > CPU: 4 PID: 2972 Comm: qemu-system-x86 Tainted: G OE 4.13.0-rc2+ #16 > RIP: 0010:kvm_lapic_expired_hv_timer+0x9e/0xb0 [kvm] > Call Trace: > handle_preemption_timer+0xe/0x20 [kvm_intel] > vmx_handle_exit+0xb8/0xd70 [kvm_intel] > kvm_arch_vcpu_ioctl_run+0xdd1/0x1be0 [kvm] > ? kvm_arch_vcpu_load+0x47/0x230 [kvm] > ? kvm_arch_vcpu_load+0x62/0x230 [kvm] > kvm_vcpu_ioctl+0x340/0x700 [kvm] > ? kvm_vcpu_ioctl+0x340/0x700 [kvm] > ? __fget+0xfc/0x210 > do_vfs_ioctl+0xa4/0x6a0 > ? __fget+0x11d/0x210 > SyS_ioctl+0x79/0x90 > do_syscall_64+0x81/0x220 > entry_SYSCALL64_slow_path+0x25/0x25 > ------------[ cut here ]------------ > WARNING: CPU: 4 PID: 2972 at /home/kernel/linux/arch/x86/kvm//lapic.c:1498 cancel_hv_timer.isra.40+0x4f/0x60 [kvm] > CPU: 4 PID: 2972 Comm: qemu-system-x86 Tainted: G W OE 4.13.0-rc2+ #16 > RIP: 0010:cancel_hv_timer.isra.40+0x4f/0x60 [kvm] > Call Trace: > kvm_lapic_expired_hv_timer+0x3e/0xb0 [kvm] > handle_preemption_timer+0xe/0x20 [kvm_intel] > vmx_handle_exit+0xb8/0xd70 [kvm_intel] > kvm_arch_vcpu_ioctl_run+0xdd1/0x1be0 [kvm] > ? kvm_arch_vcpu_load+0x47/0x230 [kvm] > ? kvm_arch_vcpu_load+0x62/0x230 [kvm] > kvm_vcpu_ioctl+0x340/0x700 [kvm] > ? kvm_vcpu_ioctl+0x340/0x700 [kvm] > ? __fget+0xfc/0x210 > do_vfs_ioctl+0xa4/0x6a0 > ? __fget+0x11d/0x210 > SyS_ioctl+0x79/0x90 > do_syscall_64+0x81/0x220 > entry_SYSCALL64_slow_path+0x25/0x25 > > This patch fixes it by making the caller of start_hv_timer and start_sw_timer > be in preemption-disabled regions, which trivially avoid any reentrancy > issue with preempt notifier. > > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> > Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> I've hit this warning today, and your patch seems fixing it. Tested-by: Takashi Iwai <tiwai@xxxxxxx> Thanks! Takashi
