On 6/15/20 5:40 PM, Stephen John Smoogen wrote:

On Mon, 15 Jun 2020 at 09:42, Manuel Wolfshant <wolfy@nobugconsulting.ro mailto:wolfy@nobugconsulting.ro> wrote:

On 6/15/20 2:46 PM, Stephen John Smoogen wrote:

I got inspired by Adi's earlier suggestion and after reading
https://access.redhat.com/articles/3311301 I've tried today all
variants of disabling the spectre mitigations. Whatever I do,
immediately after a reboot, yum reinstall kernel does not take
less than 5 minutes :( It goes down to 2 min if I repeat the
operation afterwards so I guess some caching kicks in. I will try
later today the kernels from elrepo and maybe even xen.crc.id.au
<http://xen.crc.id.au> ( I kind of hate the "disable selinux"
recommendation from the install page so I postponed it in the hope
of other solution ).

If you can do a full reinstall, could you see if a KVM host/guest combo has the same problem? That would at least point the finger more firmly at VT, spectre or something else.

I finally managed to install a fresh KVM host / guest pair on an identical blade ( HS21XM, 64 GB ram, 2*E5450@ 3.00GHz ). Here are the results I see:

1. KVM host, stock instalation and fully updated, kernel 3.10.0-1127.10.1 #cd /sys/kernel/debug/x86/ #cat ibrs_enabled pti_enabled retp_enabled 0 1 1

#time yum -y reinstall kernel-3.10.0-1127.el7.x86_64 real    0m50.026s user    0m32.872s sys     0m23.312s

2. KVM guest on the same machine (virt-install --name guest1-rhel7 --memory 2048 --vcpus 2  --disk size=20 --network=bridge:br0 --pxe --os-variant rhel7 <=== copy/paste from https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/htm... ), stock installation and fully updated with absolutely no change towards the defaults including same ibrs_enabled pti_enabled retp_enabled as the host, , kernel 3.10.0-1127.10.1

#time yum -y reinstall kernel-3.10.0-1127.el7.x86_64 real    2m39.644s user    1m54.662s sys     1m32.496s

3. Xen Domu,  3.10.0-1127.8.2.el7.x86_6 ( but results are consistent across all kernels )

# cat ibrs_enabled pti_enabled retp_enabled 0 0 0

# time yum -y reinstall kernel-3.10.0-1127.el7.x86_64 real    5m44.030s user    2m9.931s sys     4m7.771s

4. Dom0, 4.9.215-36.el7.x86_64, , xen 4.12 from centos' repo

# time  yum -y reinstall kernel-3.10.0-1127.el7.x86_64 real    1m52.417s user    0m45.704s sys     1m32.167s