linux-kernel - Re: KVM Nested L2 guest startup problems

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Message-ID: <CAESbUUzDm0REihDHinZ+fmQL8MWqn4kYCY8mQaVEnmVr4hh7NA@mail.gmail.com>
Date:	Sun, 4 May 2014 17:57:58 +0300
From:	Abel Gordon <abel@...atoscale.com>
To:	Hu Yaohui <loki2441@...il.com>
Cc:	Bandan Das <bsd@...hat.com>, Paolo Bonzini <pbonzini@...hat.com>,
	kvm <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Muli Ben-Yehuda <muli@...atoscale.com>
Subject: Re: KVM Nested L2 guest startup problems

On Fri, May 2, 2014 at 11:11 PM, Hu Yaohui <loki2441@...il.com> wrote:
>
> On Fri, May 2, 2014 at 2:39 PM, Bandan Das <bsd@...hat.com> wrote:
> > Hu Yaohui <loki2441@...il.com> writes:
> >
> >> On Fri, May 2, 2014 at 11:52 AM, Paolo Bonzini <pbonzini@...hat.com> wrote:
> >>> Il 02/05/2014 17:17, Hu Yaohui ha scritto:
> >>>
> >>>> Hi Paolo,
> >>>> I have tried L0 with linux kernel 3.14.2 and L1 with linux kernel 3.14.2
> >>>> L1 QEMU qemu-1.7.0
> >>>> L2 QEMU qemu-1.7.0.
> >>>
> >>>
> >>> Do you mean L0 and L1?
> >> Yes.
> >>>
> >>> What is your QEMU command line, and what is the processor?  Also, what guest
> >>> you are running?
> >>>
> >> L0 host
> >> - Debian 7 with linux kernel 3.14.2
> >> - 24 pCPU, 120G pMEM
> >> - cpu mode: Intel(R) Xeon(R) CPU E5-2620 v2 @ 2.10GHz
> >
> > Ivy Bridge-EP ? Looks similar to
> > https://bugzilla.kernel.org/show_bug.cgi?id=73331
> >
> > Just out of curiosity, any difference if you run with ept=0 ?
> I have tried it. The same error with L0 kvm ept=1 and L1 kvm ept=0
> Do you have any idea how the Ivy Bridge-EP problem is solved?

I experienced a similar problem that was related to nested code
having some bugs related to apicv and other new vmx features.

For example, the code enabled posted interrupts to run L2 even when the
feature was not exposed to L1 and L1 didn't use it.

Try changing prepare_vmcs02  to force disabling posted_interrupts,
code should looks like:

....
....
exec_control = vmcs12->pin_based_vm_exec_control;
exec_control |= vmcs_config.pin_based_exec_ctrl;
exec_control &= ~(PIN_BASED_VMX_PREEMPTION_TIMER|PIN_BASED_POSTED_INTR);
vmcs_write32(PIN_BASED_VM_EXEC_CONTROL, exec_control);
....
...

and also

...
...
exec_control &= ~(SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
     SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
     SECONDARY_EXEC_APIC_REGISTER_VIRT |
     SECONDARY_EXEC_PAUSE_LOOP_EXITING);
...
...


We also experienced issues using apicv for L1 while running a L2 guest
with no apicv, so also load kvm_intel with enable_apicv=0


Hope this solves your problem...
You are welcome to upstream the changes if it does :)

> >
> >> - QEMU command line of L1
> >> $ sudo qemu-system-x86_64 -machine accel=kvm -drive
> >> file=vdisk.img,if=virtio -m 4096 -smp 10 -net
> >> nic,model=virtio,macaddr=52:54:00:12:34:80 -cpu kvm64,+vmx -net
> >> tap,ifname=qtap0,script=no,downscript=no -vnc :2
> >>
> >> L1 guest
> >> - Ubuntu 10.04 with linux kernel 3.14.2
> >> - QEMU command line of L2
> >> $qemu-system-x86_64  -machine accel=kvm -smp 2 -boot c -drive
> >> file=/home/nested/vmdisks/vdisk1-virtnet.img,if=virtio -m 2048 -vnc :4
> >> -net nic,model=virtio,macaddr=52:54:00:12:34:90 -net
> >> tap,ifname=qtap0,script=no,downscript=no
> >>
> >> L2 guest
> >> - Ubuntu 10.04 with linux kernel 2.6.32
> >>> Paolo
> >>>
> >>>
> >>>> I still get the same error when running qemu in L1 guest.
> >>>
> >>>
> >> --
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