Re: [Qemu-devel] Question about qemu firmware configuration (fw_cfg) device

[Alexander Graf]

On 17.07.2010, at 11:53, Richard W.M. Jones wrote:

> On Sat, Jul 17, 2010 at 10:50:59AM +0100, Richard W.M. Jones wrote:
>> I understand from the git logs that fw_cfg was added because the old
>> way was to load kernel & initrd into RAM directly, but this didn't
>> work because SeaBIOS would clear the RAM, clobbering kernel & initrd.
>> Could we change to loading these directly into RAM, and instead
>> provide some indication to SeaBIOS so it doesn't clobber the RAM?  I'm
>> quite prepared to do the work, just wondering if there's something
>> else I'm not getting about this.
> 
> Or thinking around the subject:
> 
> Change fw_cfg so that you send a command + a physical address, and
> fw_cfg memcpy's the kernel / initrd / etc to that physical address.
> Then linuxboot.bin doesn't have to do the manual copying.
> 
> Or just change linuxboot.bin so it does 32 bit inl instructions, which
> might at least be a bit faster ...

I don't see why it would be slow. ins should be emulated using coalesced mmio, 
no?

Alex