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Hi Jean-Louis,

Thanks for sharing this info.

If I look at my set of servers then we also have CentOS 6 servers which used to crash after 3 or 4 weeks.

However with the 4.9.112-32.el6.x86_64 kernel and Xen 4.8.4-1.el6 it looks to be more stable with 65+ days of uptime on six servers running that particular setup.

I still think that the 4.8.4-pre Xen package for Debian is the stable version, so if you think of upgrading to 4.8.5-pre I would not recommend it yet.

Best regards,

		Roalt Zijlstra
		Teamleader Infra & Deliverability

		roalt.zijlstra@xxxxxxxxxxx
		+31 342 423 262
		roalt.zijlstra
		https://www.webpower-group.com

Op di 30 okt. 2018 om 12:12 schreef Jean-Louis Dupond <jean-louis@xxxxxxxxx>:

Hi Roalt,

We are running Xen 4.6 on 4.9.x kernel and CentOS 6, and are having the same issues.
But not that frequent as you state. Only like once every month.

The systems (Dell R630) also crashes/resets without any message. So nothing is logged unfortunately :(

The crashes were not observed on Xen 4.4.

We configured the servers to print kernel logs to SOL (Serial Over LAN via iDRAC), and we log those.
But since then no crashed servers anymore, so we don't know yet if this will give us some more details.

Thanks
Jean-Louis

On 29/10/18 12:57, Roalt Zijlstra | webpower wrote:
Hi there,

Ever since all the Meltdown and Spectre kernel updates and possibly also Xen 4.8 updates, we experience crashes of the Dom0 just out of the blue. Sometimes after 1 day, sometimes after a few days or even 14 days, completely random.

We have two Dell P730 servers and two Dell P720 servers with this behaviour. One thing is that we updated these machine to the latest available firmware, because that is the most secure way. Then we installed Debian Stretch with Xen 4.8 support

We have done serveral installs and 4 servers seem to crash pretty fast and other don't. In the end we think that we can lead it back to the xen-4.8.4-pre version being stable and the xen-4.8.5-pre being unstable. This was kinda independent of the kernel that we were using 4.14 or 4.9.0-8-amd64. This is off course all Debian package numbering.

As last resort we updated on one server all DomU kernels of our Jessie servers on this Dom0 to 4.9.0 from backports instead of the 3.16 kernel. For now that seems to work, but the crashes are random so it could happen any time again. The idea is that these kernels are completely spectre& meltdown unaware and might cause trouble in Xen kernel support. I am not sure if this is true at all, but we are pretty lost what the actual cause is.

We also tested with CentOS and we also had these crashes there with certain combinations of kernel/Xen. The most recent updates seem to be more stable tough. The most frustrating part is the there is absolutely no logs to be found. No kernel oops or what.. the server just resets and boots again.

Are there others experiencing problems like this? Do you see more frequent server/kernel crashes on production servers?

Best regards,

Roalt Zijlstra
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Re: [Xen-users] Dom0 crashes without logging lately on Debian Stretch with Xen 4.8