Exposing -fw_cfg?

List, QEMU has capability to inject various blobs into firmware that configure how firmware configures itself. However, it can be also used to passthrough a specific file into the guest. For instance: -fw_cfg value=name=opt/com.example,file=/tmp/ign will make the /tmp/ign file accessible in the guest under: /sys/firmware/qemu_fw_cfg/by_name/opt/com.example/raw the @name is important here as it defines what knob is touched. For instance, /opt/ovmf tweaks OVMF, /bootorder changes the boot order, and so on. But, if the @name is in /opt/reverse.fully.qualified.domain form than this is a blob that is exposed into the guest and does not affect ACPI, SMBIOS, ... And IMO this is what makes the interface horrible. While I definitely would not expose the FW configuration knobs (we already provide a way to configure things like bootroder), the file passthrough is actually used. So far I have found out that RHCOS uses it to give the guest so called ignition file (for the sake of argument we can assume it's like a kickstart that the OS reads on the first boot and configures itself up), but there are some other potential users (for users it looks intriguing, it's a simple API that makes a file show up at well defined location inside the guest). Therefore I vouch for exposing the file passthorugh (and definitely do not mention firmware in the element or docs in any way, to not encourage users to use FW tweaking mode). However, before I design something, I'd like to hear your opinion. Michal