Howdy,
I recently went through a frustrating experience trying to get Xen 4 running on a CentOS 7 system. After a fresh install, fully updating the system, rebooting, then trying to install Xen4CentOS it would fail to boot into the 4.9 kernel, sitting there with a blinking cursor indefinitely.
I thought it was a failure with grub, but it turns out this was set in the grub config:
GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT="console=hvc0 ..."
So the kernel was loading successfully, but it was failing boot properly (hanging because it couldn't find the / file system, but that's a different story). Boot messages were not being displayed on my console because of the console=hvc0 setting, hampering the troubleshooting process.
What is the purpose of setting console=hvc0? I removed it so I could trouble shoot this problem, but I didn't re-add it and the system booted fine, Xen is working. Is there something that depends on this?
I always disable "rhgb quiet" on a fresh install because I don't like boot messages being hidden from me, and now this other thing does it. I like details, I need the details, don't hide them from me.
Thanks, Jerry