Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756834AbdLOQpF (ORCPT ); Fri, 15 Dec 2017 11:45:05 -0500 Received: from mail-wr0-f193.google.com ([209.85.128.193]:39686 "EHLO mail-wr0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756697AbdLOQpC (ORCPT ); Fri, 15 Dec 2017 11:45:02 -0500 X-Google-Smtp-Source: ACJfBosId1+mfDHjl2ki+MhD4hSp+9wzz6etlbjFjdyIBd4VIgbW6s46qyDkvWJp20IDeqyVJIxT4Q== Date: Fri, 15 Dec 2017 17:44:58 +0100 From: Ingo Molnar To: Andy Lutomirski Cc: Dmitry Vyukov , Wanpeng Li , David Hildenbrand , Linus Torvalds , Thomas Gleixner , syzbot , Borislav Petkov , Dmitry Safonov , Peter Anvin , Linux Kernel Mailing List , Kyle Huey , Ingo Molnar , syzkaller-bugs@googlegroups.com, the arch/x86 maintainers , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , KVM list , "Lan, Tianyu" , James Mattson Subject: Re: BUG: unable to handle kernel paging request in __switch_to Message-ID: <20171215164458.gyqzt2c5h3clpesc@gmail.com> References: <1036ed60-035c-70a0-0a5f-00efe8ebf4da@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2813 Lines: 79 * Andy Lutomirski wrote: > On Fri, Dec 15, 2017 at 2:02 AM, Dmitry Vyukov wrote: > > On Fri, Dec 15, 2017 at 10:58 AM, Wanpeng Li wrote: > >> 2017-12-15 17:51 GMT+08:00 David Hildenbrand : > >>> > >>>> int main() > >>>> { > >>>> int fd = open("/dev/kvm", 0x80102ul); > >>>> int vm = ioctl(fd, KVM_CREATE_VM, 0); > >>>> int cpu = ioctl(vm, KVM_CREATE_VCPU, 4); > >>> > >>> Not even a memory region :) So maybe the first memory access directly > >>> triggers a fault? > >>> > >>>> ioctl(cpu, KVM_RUN, 0); > >>>> return 0; > >>>> } > >>>> > >>>> And, yes, this in fact triggers instant reboot of kernel (running in qemu). > >>>> Am I missing something here? > >>>> > >>>> +kvm maintainers, you can see full thread here: > >>>> https://groups.google.com/forum/#!topic/syzkaller-bugs/_oveOKGm3jw > >> > >> I didn't see any issue after running the test. > > > > Yes, it's strange. But I can reproduce it. There must be something > > different in our setups. > > Here is how to build exact same kernel: > > https://groups.google.com/d/msg/syzkaller-bugs/_oveOKGm3jw/vc1tXvsbCgAJ > > > > Here is how I start qemu: > > > > qemu-system-x86_64 -hda wheezy.img -net > > user,host=10.0.2.10,hostfwd=tcp::10022-:22 -net nic -nographic -kernel > > arch/x86/boot/bzImage -append "kvm-intel.nested=1 > > kvm-intel.unrestricted_guest=1 kvm-intel.ept=1 > > kvm-intel.flexpriority=1 kvm-intel.vpid=1 > > kvm-intel.emulate_invalid_guest_state=1 kvm-intel.eptad=1 > > kvm-intel.enable_shadow_vmcs=1 kvm-intel.pml=1 > > kvm-intel.enable_apicv=1 console=ttyS0 root=/dev/sda > > earlyprintk=serial slub_debug=UZ vsyscall=native rodata=n oops=panic > > panic_on_warn=1 panic=86400" -enable-kvm -pidfile vm_pid -m 2G -smp 4 > > -cpu host -usb -usbdevice mouse -usbdevice tablet -soundhw all > > > > The image is here: > > https://github.com/google/syzkaller/blob/master/docs/syzbot.md#crash-does-not-reproduce > > > > Host cpu is Intel(R) Xeon(R) CPU E5-2690 v3 > > Looking more closely, you seem to be testing this: > > commit d127129e85a020879f334154300ddd3f7ec21c1e (HEAD, tag: next-20171129) > Author: Stephen Rothwell > Date: Wed Nov 29 14:09:56 2017 +1100 > Add linux-next specific files for 20171129 > > which is almost certainly missing this fix: > > https://lkml.kernel.org/r/bc7296f4c8d86af71c31a17588c79d89c0890edc.1512109321.git.luto@kernel.org > > on account of the fix being sent the day after the tag. > > The symptoms you're seeing are definitely consistent with a screwed up > TSS after VM exit. Note that this should all be fixed in WIP.x86/pti. If you have: 5ed1fcd523b9: x86/entry: Fix assumptions that the HW TSS is at the beginning of cpu_tss then you should be fine. Thanks, Ingo