Re: [Qemu-devel] [RFC PATCH v2 00/12] Guest startup time optimization

[Chao Peng]

> > > 1) qboot optimizations: adopt the fw_cfg DMA interface instead of
> > > the
> > > cbfs flash hack (so that -kernel works), drop PCI bridge
> > > initialization,
> > > copy less than 64K of memory from ROM to 0xf0000;
> > 
> > I can do the evaluation on qboot. Also adding Amnon Ilan, to see if
> > there is some thing we can do for SeaBios.
> 
> AFAIK latest seabios already supports DMA.
> It's easy to add more config options for seabios
> if you are so inclined.

Yes, I tried that, the fw_cfg overhead in SeaBios/linuxboot optrom is
already not a big issue for us. However, there are still some other
code in SeaBIOS needs to be investigated.
> 
> > 
> > > 
> > > 
> > > 2) Linux optimizations: using an uncompressed image to avoid the
> > > cost
> > > of
> > > copying and decompressing.  QEMU can already load the image at
> > > the
> > > right
> > > place and the real mode stub can do little more than GDT/IDT
> > > setup.
> > 
> > This works surely. I actually followed your suggestion in v1 to
> > make
> > kernel multiboot-compatible and then load that kernel in QEMU
> > directly
> > (Also skipped firmware but some changes in patch 11 would move from
> > QEMU to guest kernel). This way we also gain benefit of doing mmap
> > kernel as you talked below. Not sure if this is something you can
> > accpet.
> 
> I'm not sure I understand the question here. Accept what?
> 

I mean loading a multiboot kernel without the need for firmaware.

Thanks,
Chao