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

[Gleb Natapov]

On Tue, Oct 11, 2011 at 03:14:52PM +0200, Alexander Graf wrote:
> > rep/ins is effectively equivalent to DMA except in how it's handled within 
> > QEMU.
> 
> 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.
> 
Not only granularity, but double copy too. May be Anthony is referring
to real HW in which case I also do not see how it can be true since one
operation is synchronous and another is not.

--
                        Gleb.