Re: [nVMX] With 3.20.0-0.rc0.git5.1 on L0, booting L2 guest results in L1 *rebooting*

From: Bandan Das <bsd@redhat.com>
To: Kashyap Chamarthy <kchamart@redhat.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>,
	kvm@vger.kernel.org, dgilbert@redhat.com
Subject: Re: [nVMX] With 3.20.0-0.rc0.git5.1 on L0, booting L2 guest results in L1 *rebooting*
Date: Tue, 17 Feb 2015 13:00:36 -0500	[thread overview]
Message-ID: <jpg4mqko1tn.fsf@redhat.com> (raw)
In-Reply-To: <20150217112426.GL21838@tesla.redhat.com> (Kashyap Chamarthy's message of "Tue, 17 Feb 2015 12:24:26 +0100")

Kashyap Chamarthy <kchamart@redhat.com> writes:
..
>> 
>> Does enable_apicv make a difference?
>
> Actually, I did perform a test (on Paolo's suggestion on IRC) with
> enable_apicv=0 on physical host, and it didn't make any difference:
>
> $ cat /proc/cmdline 
> BOOT_IMAGE=/vmlinuz-3.20.0-0.rc0.git5.1.fc23.x86_64 root=/dev/mapper/fedora--server_dell--per910--02-root ro console=ttyS1,115200n81 rd.lvm.lv=fedora-server_dell-per910-02/swap rd.lvm.lv=fedora-server_dell-per910-02/root LANG=en_US.UTF-8 enable_apicv=0

I am not sure if this works ? enable_apicv is a kvm_intel module parameter

>> Is this a regression caused by the commit, or do you only see it with
>> very recent kvm.git?
>
> Afraid, I didn't bisect it, but I just wanted to note that the above
> specific WARN was introduced in the above commit.

You could try an upstream kernel before the recent MSR load/store changes
to narrow down the problem.

Bandan

> I'm sure this Kernel (on L0) does not exhibit the problem:
> kernel-3.17.4-301.fc21.x86_64. But, if I had either of these two Kernels
> on the physical host, then the said problem manifests (L1 reboots):
> 3.19.0-1.fc22 or kernel-3.20.0-0.rc0.git5.1.fc23