Re: [Qemu-devel] Use of flash for x86 BIOS (was: [PATCH 0/2] Implement migration support for pflash_cfi01)

[Jordan Justen]

On Thu, Mar 21, 2013 at 12:45 AM, Markus Armbruster <address@hidden> wrote:
> x86 maintainers may wish to *switch it off* until it's done fully and
> properly, by setting "pc-sysfw" property "rom_only" to 1.

This would completely disable the flash support. At the time this
feature was added, I think it was well understood that kvm would not
support the flash mode, while plain qemu could. If it was not a
show-stopper to integrating the feature originally, what has changed?

rom_only was added as part of the flash support enabling. I guess in a
way it would be amusing to use it to disabled that same feature.

> 1. The "pc-sysfw" device is mostly harmless.

Indeed, and it's only marginally of interest until kvm supports it.

Admittedly, I've been completely ineffectual in resolving the kvm
portion. More recently I tried to make use of KVM_MEM_READONLY to
address this. I was able to get an VM exit on writes to flash, but not
able to get the memory region to convert to full device mode so VM
exits would occur on reads as well. I am once again stalled...

-Jordan