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

Avi Kivity
2008-12-22T19:46:27Z

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.