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authorWanpeng Li <wanpeng.li@hotmail.com>2017-07-25 00:43:15 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2017-07-26 19:04:53 +0200
commit1d518c6820daf4e00d29adfba980aee05f605f0f (patch)
tree333338fc418884c9707abaaf5fea5f21b6580087 /arch
parent67fbcd62f54d4503e3dc63b68af1c6757b74e050 (diff)
KVM: LAPIC: Fix reentrancy issues with preempt notifiers
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/lapic.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 2819d4c123eb..589dcc117086 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1495,11 +1495,10 @@ EXPORT_SYMBOL_GPL(kvm_lapic_hv_timer_in_use);
static void cancel_hv_timer(struct kvm_lapic *apic)
{
+ WARN_ON(preemptible());
WARN_ON(!apic->lapic_timer.hv_timer_in_use);
- preempt_disable();
kvm_x86_ops->cancel_hv_timer(apic->vcpu);
apic->lapic_timer.hv_timer_in_use = false;
- preempt_enable();
}
static bool start_hv_timer(struct kvm_lapic *apic)
@@ -1507,6 +1506,7 @@ static bool start_hv_timer(struct kvm_lapic *apic)
struct kvm_timer *ktimer = &apic->lapic_timer;
int r;
+ WARN_ON(preemptible());
if (!kvm_x86_ops->set_hv_timer)
return false;
@@ -1538,6 +1538,8 @@ static bool start_hv_timer(struct kvm_lapic *apic)
static void start_sw_timer(struct kvm_lapic *apic)
{
struct kvm_timer *ktimer = &apic->lapic_timer;
+
+ WARN_ON(preemptible());
if (apic->lapic_timer.hv_timer_in_use)
cancel_hv_timer(apic);
if (!apic_lvtt_period(apic) && atomic_read(&ktimer->pending))
@@ -1552,15 +1554,20 @@ static void start_sw_timer(struct kvm_lapic *apic)
static void restart_apic_timer(struct kvm_lapic *apic)
{
+ preempt_disable();
if (!start_hv_timer(apic))
start_sw_timer(apic);
+ preempt_enable();
}
void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
{
struct kvm_lapic *apic = vcpu->arch.apic;
- WARN_ON(!apic->lapic_timer.hv_timer_in_use);
+ preempt_disable();
+ /* If the preempt notifier has already run, it also called apic_timer_expired */
+ if (!apic->lapic_timer.hv_timer_in_use)
+ goto out;
WARN_ON(swait_active(&vcpu->wq));
cancel_hv_timer(apic);
apic_timer_expired(apic);
@@ -1569,6 +1576,8 @@ void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
advance_periodic_target_expiration(apic);
restart_apic_timer(apic);
}
+out:
+ preempt_enable();
}
EXPORT_SYMBOL_GPL(kvm_lapic_expired_hv_timer);
@@ -1582,9 +1591,11 @@ void kvm_lapic_switch_to_sw_timer(struct kvm_vcpu *vcpu)
{
struct kvm_lapic *apic = vcpu->arch.apic;
+ preempt_disable();
/* Possibly the TSC deadline timer is not enabled yet */
if (apic->lapic_timer.hv_timer_in_use)
start_sw_timer(apic);
+ preempt_enable();
}
EXPORT_SYMBOL_GPL(kvm_lapic_switch_to_sw_timer);