Re: [Qemu-devel] Slow kernel/initrd loading via fw_cfg; Was Re: Hack integrating SeaBios / LinuxBoot option rom with QEMU trace backends

[Anthony Liguori <anthony@codemonkey.ws>]

On 10/11/2011 08:23 AM, Avi Kivity wrote:
> On 10/11/2011 03:19 PM, Anthony Liguori wrote:
>>> No, DMA has a lot bigger granularities in kvm/user interaction. We
>>> can easily DMA a 50MB region with a single kvm/user exit. For PIO we
>>> can at most do page granularity.
>>
>>
>> So make a proper PCI device for kernel loading.  It's a much more
>> natural approach and let's use alias -kernel/-initrd/-append to
>> -device kernel-pci,kernel=PATH,initrd=PATH
>
> This is overkill.  First let's optimize rep/movs before introducing any
> more interfaces.  If that doesn't work, then we can have a dma interface
> for fwcfg.  But a new pci device?

This is how it would work on bare metal.  Why is a PCI device overkill compared 
to a dma interface for fwcfg?

If we're adding dma to fwcfg, then fwcfg has become far too complex for it's 
intended purpose.

Regards,

Anthony Liguori

>