https://github.com/torvalds/linux
Revision 1d518c6820daf4e00d29adfba980aee05f605f0f authored by Wanpeng Li on 25 July 2017, 07:43:15 UTC, committed by Paolo Bonzini on 26 July 2017, 17:04:53 UTC
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 cancel_hv_timer, 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@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
[Add more WARNs. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 parent 67fbcd6
Tip revision: 1d518c6820daf4e00d29adfba980aee05f605f0f authored by Wanpeng Li on 25 July 2017, 07:43:15 UTC
KVM: LAPIC: Fix reentrancy issues with preempt notifiers
KVM: LAPIC: Fix reentrancy issues with preempt notifiers
Tip revision: 1d518c6
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| .cocciconfig | -rw-r--r-- | 59 bytes |
| .get_maintainer.ignore | -rw-r--r-- | 31 bytes |
| .gitattributes | -rw-r--r-- | 30 bytes |
| .gitignore | -rw-r--r-- | 1.3 KB |
| .mailmap | -rw-r--r-- | 8.1 KB |
| COPYING | -rw-r--r-- | 18.3 KB |
| CREDITS | -rw-r--r-- | 96.2 KB |
| Kbuild | -rw-r--r-- | 2.2 KB |
| Kconfig | -rw-r--r-- | 252 bytes |
| MAINTAINERS | -rw-r--r-- | 410.5 KB |
| Makefile | -rw-r--r-- | 58.8 KB |
| README | -rw-r--r-- | 722 bytes |
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