On Wed, Feb 25, 2015 at 10:40:34PM +0000, Matt Fleming wrote: > > Right, I was thinking about this in the context of configuring the BIOS > (OVMF in my case) with runtime tunable knobs instead of having to > recompile the BIOS image from scratch. > > I'll carve out some time to review your patches Gabriel.
Thanks ! Although the more I think about it, the more I like the idea of simply adding a generic named blob to fw_cfg from the host side (rather than adding a dedicated "-guestenv 'foo=bar'" option. If I make sure the generic "-fwcfg name='blob-name',file=./blob_file" is processed *after* everything else is already inserted into fw_cfg, and that we throw an error if 'blob-name' collides with anything already added during qemu setup, there's no reason I can't pass a blob named 'etc/guest-info'. So I'll send out a v2 attempting to do that, which should take care of both of our needs on the host side. On the guest side, you should be taken care of -- read whatever you need to read from fw_cfg using the BIOS's existing mechanisms. For myself, I'm tempted to write a kernel driver to allow me to simply "cat /sys/firmware/fw_cfg/etc/guestinfo | grep '^key_name='" when I need to retrieve a guest environment variable. However, I'd first need to figure out how to do the equivalent thing on Windows, and whether the requirement to add a kernel module is worth it when my main purpose is making it easy to recycle VMWare VMs which use "vmware-tools --cmd info-get guestinfo.key_name" :) Maybe it's better to stick with accessing the fw_cfg io ports from guest-side userspace, so patch 2/2 should stand as is (modulo Daniel's suggestion to make it a separate binary from "qemu-ga", of course). Thanks, --Gabriel
