We have SLES 11 SP3 installed on a Blade server. In this OS we has also create KVM vm’s and more than 5 vm’s are installed and running. Now I would like to upgrade the Host OS from SLES 11 SP3 to SLES 11 SP4. I would like to do this either online or with SLES 11 SP4 CD and expect minimal issues with upgrade. Is this possible ?
Hi and welcome to the Forum 
If it’s just running virtual machines with KVM, I would not expect issues, aside from having the vm’s shutoff while doing the upgrade.
I suggest you first review the release notes and upgrade documentation first;
https://www.suse.com/releasenotes/x86_64/SUSE-SLES/11-SP4/
https://www.suse.com/documentation/sles11/book_sle_deployment/data/sec_update_sle11sp3.html
I would also snapshot/backup the vm’s, any system configuration changes and important data.