Enable direct iSCSI support via net-libs/libiscsi instead of indirectly via the Linux block layer that sys-block/open-iscsi does.

Packages describing “iscsi” as local USE flag

Package “iscsi” Flag Description
app-emulation/qemu Enable direct iSCSI support via net-libs/libiscsi instead of indirectly via the Linux block layer that sys-block/open-iscsi does.
app-emulation/libvirt Allow using an iSCSI remote storage server as pool for disk image storage
sys-cluster/cinder Allow using an iSCSI remote storage server as pool for disk image storage
sys-cluster/nova Installs iscsi helper udev scripts

All packages providing a “iscsi” USE flag (2)