diff options
| author | Wanpeng Li <wanpeng.li@hotmail.com> | 2017-05-20 20:32:32 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-04-13 19:48:07 +0200 |
| commit | 5ea0519a77de6d34204012b7223ba72d0ef607dd (patch) | |
| tree | db0d8ae962478e373ec6730e18acda0edde198a4 /arch/x86/kvm/lapic.c | |
| parent | 6391346223496fdf4ac510ad4fae161daba23f80 (diff) | |
KVM: X86: Fix preempt the preemption timer cancel
[ Upstream commit 5acc1ca4fb15f00bfa3d4046e35ca381bc25d580 ]
Preemption can occur during cancel preemption timer, and there will be
inconsistent status in lapic, vmx and vmcs field.
CPU0 CPU1
preemption timer vmexit
handle_preemption_timer(vCPU0)
kvm_lapic_expired_hv_timer
vmx_cancel_hv_timer
vmx->hv_deadline_tsc = -1
vmcs_clear_bits
/* hv_timer_in_use still true */
sched_out
sched_in
kvm_arch_vcpu_load
vmx_set_hv_timer
write vmx->hv_deadline_tsc
vmcs_set_bits
/* back in kvm_lapic_expired_hv_timer */
hv_timer_in_use = false
...
vmx_vcpu_run
vmx_arm_hv_run
write preemption timer deadline
spurious preemption timer vmexit
handle_preemption_timer(vCPU0)
kvm_lapic_expired_hv_timer
WARN_ON(!apic->lapic_timer.hv_timer_in_use);
This can be reproduced sporadically during boot of L2 on a
preemptible L1, causing a splat on L1.
WARNING: CPU: 3 PID: 1952 at arch/x86/kvm/lapic.c:1529 kvm_lapic_expired_hv_timer+0xb5/0xd0 [kvm]
CPU: 3 PID: 1952 Comm: qemu-system-x86 Not tainted 4.12.0-rc1+ #24 RIP: 0010:kvm_lapic_expired_hv_timer+0xb5/0xd0 [kvm]
Call Trace:
handle_preemption_timer+0xe/0x20 [kvm_intel]
vmx_handle_exit+0xc9/0x15f0 [kvm_intel]
? lock_acquire+0xdb/0x250
? lock_acquire+0xdb/0x250
? kvm_arch_vcpu_ioctl_run+0xdf3/0x1ce0 [kvm]
kvm_arch_vcpu_ioctl_run+0xe55/0x1ce0 [kvm]
kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
? kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
? __fget+0xf3/0x210
do_vfs_ioctl+0xa4/0x700
? __fget+0x114/0x210
SyS_ioctl+0x79/0x90
do_syscall_64+0x8f/0x750
? trace_hardirqs_on_thunk+0x1a/0x1c
entry_SYSCALL64_slow_path+0x25/0x25
This patch fixes it by disabling preemption while cancelling
preemption timer. This way cancel_hv_timer is atomic with
respect to kvm_arch_vcpu_load.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/kvm/lapic.c')
| -rw-r--r-- | arch/x86/kvm/lapic.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index b24b3c6d686e..5c3d416fff17 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -1363,8 +1363,10 @@ EXPORT_SYMBOL_GPL(kvm_lapic_hv_timer_in_use); static void cancel_hv_tscdeadline(struct kvm_lapic *apic) { + preempt_disable(); kvm_x86_ops->cancel_hv_timer(apic->vcpu); apic->lapic_timer.hv_timer_in_use = false; + preempt_enable(); } void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu) |