Re: [Qemu-devel] [PATCH v2] vl.c: disallow command line fw cfg without opt/

[Paolo Bonzini <pbonzini@redhat.com>]

I frankly think it's overengineered, but it's already much better and if
it helps converging to a compromise why not.

Alternatives to your proposals follow:

On 17/03/2016 14:13, Michael S. Tsirkin wrote:
> 
> QEMU command line:
> 	A. -fw-cfg RFQDN/PATH prepends usr/. So users will not get conflicts
> 	   with QEMU hardware

Alternative: no need to prepend usr/, I think.

> 	B. -fw-cfg org.qemu/unsupported/XXX as a hack, removes
> 		org.qemu/unsupported/ and leaves just XXX,
> 		for people who want to break^?^?^?^?^?debug QEMU hardware

Alternative: fail on:

- a blacklist of etc/* files including etc/system-states,
etc/smbios/smbios-tables, etc/smbios/smbios-anchor,
etc/reserved-memory-end, etc/pvpanic-port, etc/e820, and possibly
etc/boot-menu-wait

- on all org.qemu/* files

- iff etc/boot-menu-wait is blacklisted, fail on
org.seabios/boot-menu-wait too.

Everything else is passed through.  No hacks required.

> 	C. -fw-cfg opt/FOO accepts any path, for backwards compatibility

Implicit in my proposed alternative to A.

> 	D. any other use fails

Replaced by my alternative to B.  RFQDN is just a best practice, and it
is not enforced except as proposed in B.  For the same reason, no
changes are required in the Linux driver.

> OVMF:
> 	Can use the compatible opt/ovmf/ for now. [snip]
> 	Long term: Gradually transition OVMF to look up paths in usr/org.uefi/:
> 	if nothing is found there, look up in opt/ovmf/ for backwards
> 	compatibility.

Agreed except it would be org.tianocore.edk2.ovmf/ rather than usr/org.uefi.

Likewise SeaBIOS would switch from etc/ to an org.seabios/ prefix (for
stuff usable from both Coreboot and QEMU, e.g.
org.seabios/bootsplash.bmp) or org.qemu/ (for stuff that is specific to
QEMU).

Files that could be moved from etc/ to org.qemu/ correspond to the ones
that are blacklisted in (B), e.g. etc/system-states ->
org.qemu/system-states.

Paolo