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

[Anthony Liguori <anthony@codemonkey.ws>]

On 08/04/2010 08:07 AM, Gleb Natapov wrote:
> On Wed, Aug 04, 2010 at 08:04:09AM -0500, Anthony Liguori wrote:
>    
>> On 08/04/2010 03:17 AM, Avi Kivity wrote:
>>      
>>> For playing games, there are three options:
>>> - existing fwcfg
>>> - fwcfg+dma
>>> - put roms in 4GB-2MB (or whatever we decide the flash size is)
>>> and have the BIOS copy them
>>>
>>> Existing fwcfg is the least amount of work and probably
>>> satisfactory for isapc.  fwcfg+dma is IMO going off a tangent.
>>> High memory flash is the most hardware-like solution, pretty easy
>>>        
>> >from a qemu point of view but requires more work.
>>
>> The only trouble I see is that high memory isn't always available.
>> If it's a 32-bit PC and you've exhausted RAM space, then you're only
>> left with the PCI hole and it's not clear to me if you can really
>> pull out 100mb of space there as an option ROM without breaking
>> something.
>>
>>      
> We can map it on demand. Guest tells qemu to map rom "A" to address X by
> writing into some io port. Guest copies rom. Guest tells qemu to unmap
> it. Better then DMA interface IMHO.
>    

That's what I thought too, but in a 32-bit guest using ~3.5GB of RAM, 
where can you safely get 100MB of memory to full map the ROM?  If you're 
going to map chunks at a time, you are basically doing DMA.

And what's the upper limit on ROM size that we impose?  100MB is already 
at the ridiculously large size.

Regards,

Anthony Liguori

> --
> 			Gleb.
>