Re: [Qemu-devel] enabling bus-master IDE driver

[Juergen Keil]

> Quoting zitu <address@hidden>:
> > >
> > > Does that mean that the patch doesn't work?  Do I have to do something 
else
> > > to make dma work?
> >
> > I think this patch is almost complete for linux and solaris guests. Some
> > more work/init is needed inside XP/NT/2K. Anyone around with this
> > knowledge ?
> 
> answering to myself... :)
> 
> WIN_WRITEDMA_EXT & WIN_READDMA_EXT cases are not defined in hw/ide.c

Aha, and Windows uses these commands, on small HDDs <= 128GB ?


> I have no idea where to start to write a patch for these... :(
> 
> Until these and the atapi_dma are set/defined, no dma should work IMHO.
> And this seems not to be OS dependant.
> 
> Which means the linux figures I got were wrong ???

The *_EXT versions are apparently for HDDs with capacities >128GB, these
need 48-bit LBA addresses to access the HDD space over the 128GB mark.

I guess that Solaris/Linux uses the commands with the smaller 28-bit
LBA disk addresses for small disks with capacities <= 128GB.

An interesting experiment would be to setup a QEMU HDD image > 128GB,
then try Solaris x86/Linux with such a big disk and check if it still
works.  Probably not.