Ok. We've fixed the issue.
For those who wants to know the reason for both issues (hang on EFI and seeing no root partition).
The reason of those two issues that kernel can't read required module from disk (module to work with AHCI disks).
There are two possible solutions here:
1. Compile kernel with https://cateee.net/lkddb/web-lkddb/SATA_AHCI_PLATFORM.html enabled to Y
2. Updated your genkernel.conf as per attached mine example:
Code:
RAMDISKMODULES="yes"
# Add additional modules to the initramfs using the module groups defined
# in /usr/share/genkernel/defaults/modules_load (see this file for
# more details). This would be used if, for example, you
# required an additional crypto module or network device at boot
# time and did not want to statically compile these in the kernel.
# Options take the form AMODULES_{group} where {group} is one of
# the groups in modules_load (which are in the form MODULES_{group}).
# Use this with caution.
AMODULES_group="ahci_platform"
