Re: [Xen-users] CentOS 7 and PV HVM

[Mark Pryor <tlviewer@xxxxxxxxx>]

https://bugs.centos.org/view.php?id=13763

hello,

when C7.4 was released in early August 2017. The above bug report was

where I learned about the pv domU kernel limitation.

The CentosPlus kernel was patched soon after and that gave us a workaround. Most frustrating to me was the flaw in 7.4 bootable media and also the pxeboot images. This meant we couldn't boot into a xen pv install using the `official` media ISO's.

I went ahead to build a new pxeboot pair based on the CentosPlus repaired kernel and then I remastered the minimal ISO using those tools. Below I show my fixed pxeboot pair.

results]$ ls -al images/pxeboot/

total 110972
drwxr-xr-x 2 root root     4096 Sep 21 19:12 .
drwxr-xr-x 3 root root     4096 Sep 21 19:12 ..
-rw-r--r-- 2 root root 50955588 Sep 21 19:10 initrd.img
-rw-r--r-- 2 root root 56606612 Sep 21 19:12 upgrade.img
-rwxr-xr-x 2 root root  5928336 Sep 12  2017 vmlinuz
[mockbuild@c7min:~/results]$ file images/pxeboot/vmlinuz

images/pxeboot/vmlinuz: Linux kernel x86 boot executable bzImage, version 3.10.0-693.2.2.el7.centos.plus.x86_64 (mockbuild@xxxxxxxxxxxxxx, RO-rootFS, swap_dev 0x5, Normal VGA

Good news for us/you is this pv kernel limitation is a singular problem limited to the default C7.4 kernel and you have many options to workaround. Not only the CentosPlus kernel works to boot your domU, but also the elrepo kernel-LT and kernel-ML.

PryMar56

##xen-packaging on Freenode

On Sunday, March 18, 2018 11:48 PM, Steffan A. Cline <steffan@xxxxxxxxx> wrote:

With the changes in CentOS 7 not allowing for PV anymore, unless they fix it as the Red Hat log indicates they may, in reading I’m hearing that PVHVM is the way to go offering more advantages.

I tried using the configuration file shown on https://wiki.xen.org/wiki/Xen_Linux_PV_on_HVM_drivers but the errors returned are not very clear.

Currently I am using the kernel Linux h1.hldns.com 4.9.75-29.el7.x86_64 #1 SMP Fri Jan 5 19:42:28 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux and the Xen 4.6.6-10.el7 packages

Does anyone have a working config file for CentOS 7 I can try?

Steffan A. Cline

steffan@xxxxxxxxx

602-793-0014

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