kvm: WARNING in rtc_status_pending_eoi_check_valid

[Dmitry Vyukov]

Hello,

The following program triggers WARNING in rtc_status_pending_eoi_check_valid:
https://gist.githubusercontent.com/dvyukov/1bd04c1b36a0c2da13c6da386e1e8c08/raw/c22c7dfa28604bd2920e1c135cfff2cb2acf8bed/gistfile1.txt

On commit a25f0944ba9b1d8a6813fd6f1a86f1bd59ac25a6 (Nov 13)


Disabled LAPIC found during irq injection
------------[ cut here ]------------
WARNING: CPU: 1 PID: 6812 at arch/x86/kvm/ioapic.c:104[<        none
     >] rtc_status_pending_eoi_check_valid+0x5e/0x80
arch/x86/kvm/ioapic.c:104
Modules linked in:[ 1566.655501] CPU: 1 PID: 6812 Comm: a.out Tainted:
G        W       4.9.0-rc5+ #28
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 ffff880038367128 ffffffff834c2959 ffffffff00000001 1ffff1000706cdb8
 ffffed000706cdb0 0000000041b58ab3 ffffffff89575430 ffffffff834c266b
 ffffffff815efeb7 ffff88003db8cc58 0000000000000082 ffff88003db8cc60
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff834c2959>] dump_stack+0x2ee/0x3f5 lib/dump_stack.c:51
 [<ffffffff813fc8f4>] __warn+0x1a4/0x1e0 kernel/panic.c:550
 [<ffffffff813fcb81>] warn_slowpath_null+0x31/0x40 kernel/panic.c:585
 [<ffffffff8117fefe>] rtc_status_pending_eoi_check_valid+0x5e/0x80
arch/x86/kvm/ioapic.c:104
 [<ffffffff81180205>] __rtc_irq_eoi_tracking_restore_one+0x2e5/0x350
arch/x86/kvm/ioapic.c:135
 [<ffffffff81181cbb>] kvm_rtc_eoi_tracking_restore_one+0x6b/0x90
arch/x86/kvm/ioapic.c:144
 [<ffffffff811791ae>] kvm_apic_set_state+0x97e/0xdc0 arch/x86/kvm/lapic.c:2091
 [<     inline     >] kvm_vcpu_ioctl_set_lapic arch/x86/kvm/x86.c:2836
 [<ffffffff810db663>] kvm_arch_vcpu_ioctl+0x1ae3/0x44a0 arch/x86/kvm/x86.c:3339
 [<ffffffff8107aee7>] kvm_vcpu_ioctl+0x237/0x11c0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:2708
 [<     inline     >] vfs_ioctl fs/ioctl.c:43
 [<ffffffff81abcb44>] do_vfs_ioctl+0x1c4/0x1630 fs/ioctl.c:679
 [<     inline     >] SYSC_ioctl fs/ioctl.c:694
 [<ffffffff81abe044>] SyS_ioctl+0x94/0xc0 fs/ioctl.c:685
 [<ffffffff88143885>] entry_SYSCALL_64_fastpath+0x23/0xc6
arch/x86/entry/entry_64.S:209
---[ end trace f9208bd27a680718 ]---