kern/58639: qemufwcfg(4), mount_qemufwcfg(8): writes are not supported

[campbell+netbsd%mumble.net@localhost]

>Number:         58639
>Category:       kern
>Synopsis:       qemufwcfg(4), mount_qemufwcfg(8): writes are not supported
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Aug 25 14:05:00 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current, 10, 9
>Organization:
The NetQemuFwrite Configuration
>Environment:
>Description:
Writes to the qemu firmware configuration device or file system are not supported, even though qemu allows them for some nodes:

https://www.qemu.org/docs/master/specs/fw_cfg.html
>How-To-Repeat:
try to write to a qemu fw cfg node
>Fix:
Yes, please!

Need to implement the DMA interface.