kvm: WARNING In kvm_apic_accept_events

[Dmitry Vyukov]

Hello,

The following program triggers WARNING in kvm_apic_accept_events:
https://gist.githubusercontent.com/dvyukov/95b845a2e637485568ea1ef181a72370/raw/d90717dd67128b21715c5e794568a1600f613d97/gistfile1.txt

On commit 015ed9433be2b476ec7e2e6a9a411a56e3b5b035 (Nov 11).


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WARNING: CPU: 1 PID: 23523 at arch/x86/kvm/lapic.c:2330
kvm_apic_accept_events+0x3f6/0x460
Modules linked in:[   55.632648] CPU: 1 PID: 2812 Comm: a.out Not
tainted 4.9.0-rc4+ #41
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 ffff88006be77978 ffffffff81c2f79b 0000000000000000 0000000000000000
 ffffffff8322d6a0 ffffffff81127426 ffff88006be779c0 ffffffff8123ffef
 ffffffff811acc46 ffffffff0000091a ffffffff8322d6a0 000000000000091a
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff81c2f79b>] dump_stack+0xb3/0x118 lib/dump_stack.c:51
 [<ffffffff8123ffef>] __warn+0x19f/0x1e0 kernel/panic.c:550
 [<ffffffff812401fc>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff81127426>] kvm_apic_accept_events+0x3f6/0x460
arch/x86/kvm/lapic.c:2330
 [<     inline     >] vcpu_block arch/x86/kvm/x86.c:6793
 [<     inline     >] vcpu_run arch/x86/kvm/x86.c:6828
 [<ffffffff810b8f20>] kvm_arch_vcpu_ioctl_run+0x1580/0x5a90
arch/x86/kvm/x86.c:6984
 [<ffffffff8106091e>] kvm_vcpu_ioctl+0x61e/0xdd0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:2557
 [<     inline     >] vfs_ioctl fs/ioctl.c:43
 [<ffffffff816b16fc>] do_vfs_ioctl+0x18c/0x1040 fs/ioctl.c:679
 [<     inline     >] SYSC_ioctl fs/ioctl.c:694
 [<ffffffff816b263f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff831ebd01>] entry_SYSCALL_64_fastpath+0x1f/0xc2
arch/x86/entry/entry_64.S:209
---[ end trace b2415ddd1b26dce6 ]---