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authorRadim Krčmář <rkrcmar@redhat.com>2014-10-30 15:06:45 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2014-11-03 12:07:31 +0100
commite462755cae2bf8297a663278935ad4d59812d2f3 (patch)
tree5ab71b8f6bf93fab7ab1afa2cb84f3f8f498e540 /arch/x86/kvm/lapic.h
parent02d5d55b7e39b63feb71bc49a75f58d342527d16 (diff)
downloadlinux-e462755cae2bf8297a663278935ad4d59812d2f3.tar.bz2
KVM: x86: detect SPIV changes under APICv
APIC-write VM exits are "trap-like": they save CS:RIP values for the instruction after the write, and more importantly, the handler will already see the new value in the virtual-APIC page. This caused a bug if you used KVM_SET_IRQCHIP to set the SW-enabled bit in the SPIV register. The chain of events is as follows: * When the irqchip is added to the destination VM, the apic_sw_disabled static key is incremented (1) * When the KVM_SET_IRQCHIP ioctl is invoked, it is decremented (0) * When the guest disables the bit in the SPIV register, e.g. as part of shutdown, apic_set_spiv does not notice the change and the static key is _not_ incremented. * When the guest is destroyed, the static key is decremented (-1), resulting in this trace: WARNING: at kernel/jump_label.c:81 __static_key_slow_dec+0xa6/0xb0() jump label: negative count! [<ffffffff816bf898>] dump_stack+0x19/0x1b [<ffffffff8107c6f1>] warn_slowpath_common+0x61/0x80 [<ffffffff8107c76c>] warn_slowpath_fmt+0x5c/0x80 [<ffffffff811931e6>] __static_key_slow_dec+0xa6/0xb0 [<ffffffff81193226>] static_key_slow_dec_deferred+0x16/0x20 [<ffffffffa0637698>] kvm_free_lapic+0x88/0xa0 [kvm] [<ffffffffa061c63e>] kvm_arch_vcpu_uninit+0x2e/0xe0 [kvm] [<ffffffffa05ff301>] kvm_vcpu_uninit+0x21/0x40 [kvm] [<ffffffffa067cec7>] vmx_free_vcpu+0x47/0x70 [kvm_intel] [<ffffffffa061bc50>] kvm_arch_vcpu_free+0x50/0x60 [kvm] [<ffffffffa061ca22>] kvm_arch_destroy_vm+0x102/0x260 [kvm] [<ffffffff810b68fd>] ? synchronize_srcu+0x1d/0x20 [<ffffffffa06030d1>] kvm_put_kvm+0xe1/0x1c0 [kvm] [<ffffffffa06036f8>] kvm_vcpu_release+0x18/0x20 [kvm] [<ffffffff81215c62>] __fput+0x102/0x310 [<ffffffff81215f4e>] ____fput+0xe/0x10 [<ffffffff810ab664>] task_work_run+0xb4/0xe0 [<ffffffff81083944>] do_exit+0x304/0xc60 [<ffffffff816c8dfc>] ? _raw_spin_unlock_irq+0x2c/0x50 [<ffffffff810fd22d>] ? trace_hardirqs_on_caller+0xfd/0x1c0 [<ffffffff8108432c>] do_group_exit+0x4c/0xc0 [<ffffffff810843b4>] SyS_exit_group+0x14/0x20 [<ffffffff816d33a9>] system_call_fastpath+0x16/0x1b Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/lapic.h')
-rw-r--r--arch/x86/kvm/lapic.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 3fd6c22d187d..87e0fae1f4c6 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -22,6 +22,7 @@ struct kvm_lapic {
struct kvm_timer lapic_timer;
u32 divide_count;
struct kvm_vcpu *vcpu;
+ bool sw_enabled;
bool irr_pending;
/* Number of bits set in ISR. */
s16 isr_count;