Re: [Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO

[Avi Kivity]

Ian Jackson wrote:
> Avi Kivity writes ("[Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct 
> IO"):
>   
> > Newer Xen shouldn't have this problem though; it runs qemu in kernel 
> > mode in a dedicated 64-bit domain.
> >     
>
> I think there is continued value in being able to emulate a guest
> whose physical address space exceeds the virtual address space in the
> host.  The whole assumption that all guest accessible RAM is mapped at
> once, contiguously, is I think wrong.
>   

I agree that we shouldn't expect memory to be contiguous, in order to 
properly support hotplug.  But I see zero value in trying to support 
large memory configurations on 32-bit in 2008.  This is what 64-bit 
systems are for!  If Xen has a problem with 64-bit hosts, we can try to 
accommodate it, but to have 32-bit qemu/tcg or qemu/kvm support large 
address spaces is pointless IMO.

--
Do not meddle in the internals of kernels, for they are subtle and quick to 
panic.