On Thu, Nov 2, 2017 at 11:25 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > On 02/11/2017 19:17, Andy Lutomirski wrote: >> >> >>> On Nov 2, 2017, at 6:57 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >>> >>>> On 02/11/2017 18:56, Nadav Amit wrote: >>>> Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >>>> >>>>>> On 02/11/2017 12:27, Ilya Lesokhin wrote: >>>>>> Hi, >>>>>> Just in case anyone is interested, I've hit a WARN_ON that shouldn't happen: >>>>>> http://elixir.free-electrons.com/linux/v4.13.10/source/arch/x86/kernel/traps.c#L788 >>>>>> >>>>>> I was single stepping in GDB connected to a QEMU target >>>>>> and got the trace below inside the VM. >>>>>> >>>>>> I'm not sure If it's a kernel bug or a KVM bug and I did try to reproduce or debug it. >>>>>> >>>>>> Hypervisor was running 3.10.0-514.21.1.el7.x86_64. >>>>>> VM was running a modified 4.13.0. >>>>> >>>>> It's a KVM bug, though I'm not sure if it's easily fixable. >>>> >>>> What’s wrong with MTF? That’s what I used for debugging the Intel tests. >>> >>> Nothing, but I haven't checked if you might get the same failure on >>> AMD---which doesn't have it. >> >> Is this that old SYSCALL CVE? > > No, he's just using QEMU's gdb server and bits of DR6 sometimes sneak > into a guest that is e.g. using watchpoints. > If you have a good description of the symptoms from the guest's perspective, I can try to fix up the entry code to handle it more gracefully and to at least say something like "congrats! you just hit a QEMU bug.".
