Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?

[Avi Kivity <avi@redhat.com>]

  On 08/04/2010 12:20 AM, Gerd Hoffmann wrote:
>   Hi,
>
>>> We're already doing bulk data transfer over fw_cfg as we need to do it
>>> to transfer roms and potentially a boot splash.
>>
>> Why do we need to transfer roms? These are devices on the memory bus or
>> pci bus, it just needs to be there at the right address.
>
> Indeed.  We do that in most cases.  The exceptions are:
>
>   (1) -M somethingold.  PCI devices don't have a pci rom bar then by
>       default because they didn't not have one in older qemu versions,
>       so we need some other way to pass the option rom to seabios.

What did we do back then?  before we had the fwcfg interface?

>   (2) vgabios.bin.  vgabios needs patches to make loading via pci rom
>       bar work (vgabios-cirrus.bin works fine already).  I have patches
>       in the queue to do that.

So not an issue.

>   (3) roms not associated with a PCI device:  multiboot, extboot,
>       -option-rom command line switch, vgabios for -M isapc.

We could lay those out in high memory (4GB-512MB) and have the bios copy 
them from there.  I believe that's what real hardware does - the flash 
chip is mapped there (the reset vector is at 4GB-16) and shadowed at the 
end of the 1MB 8086 range.


-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.