kvm: WARNING in kvm_arch_vcpu_ioctl_run

[Dmitry Vyukov]

Hello,

The following program triggers WARNING in kvm_arch_vcpu_ioctl_run in
run in parallel loop:
https://gist.githubusercontent.com/dvyukov/08091eee6f38548ff9e6905c5e0eaaee/raw/8cae95f2e88eeb98c4ddc06d227670c1e248222f/gistfile1.txt

On commit e234832afb623fe5c7d1d5703d6619494d8d703f (Nov 13)

WARNING: CPU: 3 PID: 11141 at arch/x86/kvm/x86.c:6984
kvm_arch_vcpu_ioctl_run+0x1f0/0x4f50
CPU: 3 PID: 11141 Comm: syz-executor Not tainted 4.9.0-rc5+ #24
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 ffff880039cef698 ffffffff834c3959 ffffffff00000003 1ffff1000739de66
 ffffed000739de5e 0000000041b58ab3 ffffffff89576450 ffffffff834c366b
 0000000041b58ab3 ffffffff894d2830 ffffffff81590020 ffffffff810d90f0
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff834c3959>] dump_stack+0x2ee/0x3f5 lib/dump_stack.c:51
 [<ffffffff81849908>] panic+0x200/0x425 kernel/panic.c:179
 [<ffffffff813fd919>] __warn+0x1c9/0x1e0 kernel/panic.c:542
 [<ffffffff813fdb81>] warn_slowpath_null+0x31/0x40 kernel/panic.c:585
 [<ffffffff810ee930>] kvm_arch_vcpu_ioctl_run+0x1f0/0x4f50
arch/x86/kvm/x86.c:6984
 [<ffffffff8107b328>] kvm_vcpu_ioctl+0x678/0x11c0
arch/x86/kvm/../../../virt/kvm/kvm_main.c:2557
 [<     inline     >] vfs_ioctl fs/ioctl.c:43
 [<ffffffff81abdb44>] do_vfs_ioctl+0x1c4/0x1630 fs/ioctl.c:679
 [<     inline     >] SYSC_ioctl fs/ioctl.c:694
 [<ffffffff81abf044>] SyS_ioctl+0x94/0xc0 fs/ioctl.c:685
 [<ffffffff88144885>] entry_SYSCALL_64_fastpath+0x23/0xc6