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

[Avi Kivity <avi@redhat.com>]

  On 08/03/2010 10:38 PM, Anthony Liguori wrote:
>> 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.
>
>
> Not quite.  The BIOS owns the option ROM space.  The way it works on 
> bare metal is that the PCI ROM BAR gets mapped to some location in 
> physical memory by the BIOS, the BIOS executes the initialization 
> vector, and after initialization, the ROM will reorganize itself into 
> something smaller.  It's nice and clean.
>
> But ISA is not nearly as clean. 

So far so good.

> Ultimately, to make this mix work in a reasonable way, we have to 
> provide a side channel interface to SeaBIOS such that we can deliver 
> ROMs outside of PCI and still let SeaBIOS decide how ROMs get organized.

I don't follow.  Why do we need this side channel?  What would a real 
ISA machine do?  Are there actually enough ISA devices for there to be a 
problem?

>
> It's additionally complicated by the fact that we didn't support PCI 
> ROM BAR until recently so to maintain compatibility with -M older, we 
> have to use a side channel to lay out option roms.

Again I don't follow.  We can just lay out the ROMs in memory like we 
did in the past?

-- 
I have a truly marvellous patch that fixes the bug which this
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