Re: VMs freezing when host is running 4.14

[Liran Alon]

On 23/11/17 17:59, Radim KrÄmÃÅ wrote:
> 2017-11-23 16:20+0100, Marc Haber:
> > On Wed, Nov 22, 2017 at 05:43:13PM +0100, Radim KrÄmÃÅ wrote:
> > > 2017-11-22 16:52+0100, Marc Haber:
> > > > On Wed, Nov 22, 2017 at 04:04:42PM +0100, çéæ wrote:
> > > > > So all guest kernels are 4.14, or also other older kernel?
> > > >
> > > > Guest kernels are also 4.14, but the issue disappears when the host is
> > > > downgraded to an older kernel. I therefore reckoned that the guest
> > > > kernel doesn't matter, but that was before I saw the trace in the log.
> > >
> > > The two most suspicious patches since 4.13 (which I assume works) are
> > >
> > >    664f8e26b00c ("KVM: X86: Fix loss of exception which has not yet been
> > >    injected")
> >
> > That one does not revert cleanly, the line in questions seems to have
> > been removed a bit later.
> >
> > Reject is:
> > 141 [24/5001]mh@fan:~/linux/git/linux ((v4.14.1) %) $ cat arch/x86/kvm/vmx.c.rej--- arch/x86/kvm/vmx.c
> > +++ arch/x86/kvm/vmx.c
> > @@ -2516,7 +2516,7 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu)
> >          struct vcpu_vmx *vmx = to_vmx(vcpu);
> >          unsigned nr = vcpu->arch.exception.nr;
> >          bool has_error_code = vcpu->arch.exception.has_error_code;
> > -       bool reinject = vcpu->arch.exception.injected;
> > +       bool reinject = vcpu->arch.exception.reinject;
> >          u32 error_code = vcpu->arch.exception.error_code;
> >          u32 intr_info = nr | INTR_INFO_VALID_MASK;
>
> This line one can be deleted as reinject isn't used in the function.
>
> Btw. there have been already many fixes from Liran Alon for that patch
> and your case could be the one adressed in
> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.spinics.net_lists_kvm_msg159158.html&d=DwIDaQ&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=Jk6Q8nNzkQ6LJ6g42qARkg6ryIDGQr-yKXPNGZbpTx0&m=206jU1rQdk3xs1DYWbQPz1gR7Iim02XOjwn458rwgIo&s=fz1JeZiSQBwqYpkmeX8OJukyC4M8BeXSuIOKwuVaeHg&e=
>
> The patch is incorrect, but you might be able to see only its benefits.

Actually I would first attempt to check this patch of mine:
https://www.spinics.net/lists/kvm/msg159062.html
It fixes a bug of a L2 exception accidentally being delivered into L1.

Regards,
-Liran
> > > and
> > >
> > >    9a6e7c39810e ("KVM: async_pf: Fix #DF due to inject "Page not Present"
> > >    and "Page Ready" exceptions simultaneously")
> > >
> > > please try reverting them to see if it helps,
> >
> > That one reverted cleanly. I am now running the new kernel on the
> > affected machine, and I think that a second machine has joined the
> > market of being affected.
>
> That one had much lower chances of being the culprit.
>
> > Would this matter on the host only or on the guests as well?
>
> Only on the host.
>
> Thanks.