WARNING in __switch_to (2)

[syzbot]

Hello,

syzkaller hit the following crash on
37759fa6d0fa9e4d6036d19ac12f555bfc0aeafd
git://git.cmpxchg.org/linux-mmots.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1d7d9c...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for
details.
If you forward the report, please keep this part and the footer.

WARNING: CPU: 0 PID: 3192 at ./arch/x86/include/asm/fpu/internal.h:340
paravirt_write_msr arch/x86/include/asm/paravirt.h:21 [inline]
WARNING: CPU: 0 PID: 3192 at ./arch/x86/include/asm/fpu/internal.h:340
wrmsrl arch/x86/include/asm/paravirt.h:149 [inline]
WARNING: CPU: 0 PID: 3192 at ./arch/x86/include/asm/fpu/internal.h:340
load_seg_legacy arch/x86/kernel/process_64.c:255 [inline]
WARNING: CPU: 0 PID: 3192 at ./arch/x86/include/asm/fpu/internal.h:340
__switch_to+0x10bd/0x13c0 arch/x86/kernel/process_64.c:455
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 3192 Comm: syzkaller835319 Not tainted 4.15.0-rc4-mm1+ #49
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
Shutting down cpus with NMI
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user [me m
or41y .3ac65ce0s98s
]
Rebooting in 86400 seconds..
---[ end trace 2d2aa5997809e25d ]---


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzk...@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is
merged
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#syz fix: exact-commit-title
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If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug
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[Eric Biggers]

For some reason I'm not able to reproduce this crash with the reproducer and
commit given -- even after making sure I had set kvm_intel.nested=1 on the host
since the reproducer uses KVM. And syzbot only hit this from Jan 1 through
Jan 3. So I'll assume it was introduced and fixed by the x86 changes around
that time, and I'll invalidate the bug for syzbot; it will send a new report if
this crash happens again...

#syz invalid

- Eric