[elrepo] AMD EPYC Support

[nick at ramnode.com]

So we’ve discovered two issues during testing so far:

 

1.	With AES-NI enabled in BIOS and kernel-ml el6 installed (whether booted into or not), KVM guest template installs take exactly 10 minutes. libguestfs-test-tool takes 3 minutes after hanging at the section in the attached output.

With AES-NI disabled, installs take the regular time (<1 min) and libguestfs-test-tool completes in about 10 seconds.

 

2.	With the host running kernel-ml el6, new KVM guests with CPU passthrough enabled display CPU cores incorrectly after installing the OS, running yum/apt-get update, and rebooting.

 

# lscpu

Architecture:          x86_64

CPU op-mode(s):        32-bit, 64-bit

Byte Order:            Little Endian

CPU(s):                2

On-line CPU(s) list:   0

Off-line CPU(s) list:  1

 

All cores show online after another reboot. This happens whether the OS is installed via template or ISO. It happens regardless of AES being enabled or disabled. It does not happen with CPU passthrough disabled.

 

 

Has anyone seen anything like this or have any idea what additional troubleshooting steps we should take?

Regards,

Nick 

 

From: Dave Chiluk <dchiluk at indeed.com> 
Sent: Thursday, August 16, 2018 3:39 PM
To: nick at ramnode.com
Cc: EL Repo General Mailing List <elrepo at lists.elrepo.org>
Subject: Re: [elrepo] AMD EPYC Support

 

The packages for centos 6 exist, I'm curious to hear how it goes.  Considering you'll be running KVM on top of that, I'd guess there is probably some performance loss by running old version of KVM.

 

-- Change is hard --

 

Dave.

 

 

 

On Thu, Aug 16, 2018 at 2:02 PM <nick at ramnode.com <mailto:nick at ramnode.com> > wrote:

Thanks Dave. What do you think about trying kernel-ml on CentOS 6? We’re trying to do a direct swap of Intel for AMD without disrupting the existing systems (CentOS 6/kernel-lt el6 running KVM). Hoping to keep changes down to just reconfiguring networking.

 

Regards,

Nick 

 

From: elrepo-bounces at lists.elrepo.org <mailto:elrepo-bounces at lists.elrepo.org>  <elrepo-bounces at lists.elrepo.org <mailto:elrepo-bounces at lists.elrepo.org> > On Behalf Of Dave Chiluk via elrepo
Sent: Thursday, August 16, 2018 10:24 AM
To: EL Repo General Mailing List <elrepo at lists.elrepo.org <mailto:elrepo at lists.elrepo.org> >
Subject: Re: [elrepo] AMD EPYC Support

 

As hardware support is accomplished primarily through the kernel, and you've likely replaced it with an elrepo kernel the Redhat documentation would not apply.  Additionally since Epyc is such a new processor you might have better luck running the kernel-ml instead of the kernel-lt as large driver backports are typically not accepted according to the linux-stable rules.

 

If I were you and intent on running an Epyc machine I'd move up to cent 7 + the kernel-ml, or move to Ubuntu Bionic which has a 4.15 kernel where they may have attempted to backport some of the Epyc enablement.

 

Good luck,

Dave.

 

On Wed, Aug 15, 2018 at 7:15 PM <nick at ramnode.com <mailto:nick at ramnode.com> > wrote:

Hello,

 

Has anyone tried running kernel-lt 4.4 (el6) on AMD EPYC processors? RedHat documentation seems to indicate that RHEL/CentOS 6 is not supported on the EPYC lineup, but AMD’s documentation is unclear.

 

Regards,

Nick

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