Re: [Qemu-devel] vga slow with -enable-kvm

[Anthony Liguori]

Gerd Hoffmann wrote:
>   Hi,
>
> The vga display is very slow when using latest svn with kvm enabled.
> Just try to boot any linux kernel with vesafb enabled (vga=0x314 for
> address@hidden), enjoy watching the boot messages scroll.  Booting without
> kvm enabled is *faster*.
>   

Yeah, this is why we need the VGA optimization.  A tight MMIO loop in 
QEMU is actually pretty efficient.  No code translation is needed so it 
ends up being a pretty straight forward set of calls to the MMIO handler 
function.

It's hugely expensive in KVM though because you have to take a huge 
number of vmexits and they're pretty expensive.  Anyway, the VGA 
optimization will fix this nicely.

Regards,

Anthony Liguori