On Wed, Aug 04, 2010 at 08:52:44AM -0500, Anthony Liguori wrote: > On 08/04/2010 08:34 AM, Gleb Natapov wrote: > >On Wed, Aug 04, 2010 at 08:15:04AM -0500, Anthony Liguori wrote: > >>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. > >> > >This is not like DMA event if done in chunks and chunks can be pretty > >big. The code that dials with copying may temporary unmap some pci > >devices to have more space there. > > That's a bit complicated because SeaBIOS is managing the PCI devices > whereas the kernel code is running as an option rom. I don't know > the BIOS PCI interfaces well so I don't know how doable this is. > Unmapping device and mapping it at the same place is easy. Enumerating pci devices from multiboot.bin looks like unneeded churn though. > Maybe we're just being too fancy here. > > We could rewrite -kernel/-append/-initrd to just generate a floppy > image in RAM, and just boot from floppy. > May be. Can floppy be 100M? -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
