Re: [Qemu-devel] Re: [PATCH] qemu/virtio: move features to an inline function

[Avi Kivity <avi@redhat.com>]

On 08/13/2009 09:15 AM, Michael S. Tsirkin wrote:
>
>> I wonder though if mmu notifiers can be used to make it transparent...
>>      
>
> Maybe they can, but that decision belongs to KVM.
> Avi, what do you think?
>
>    

I don't see how mmu notifiers help.  You can use mmu notifiers to sync 
an external mmu to the linux pagetables, but that's not the case here.

I see the following options:

- mprotect() guest memory, trap faults, mprotect() back

Will work, but exceedingly slowly and wastefully

- add a generic user visible dirty bit tracking based on linux ptes

A lot of work, not sure if useful beyond kvm

- implement vhost dirty bit tracking

Not too difficult; not sure if it's worth the effort though

- reuse the kvm dirty bitmap

Not too difficult but introduces tight coupling between vhost and kvm 
which might slow down development

- drop to userspace for live migration

Reuse qemu code, lose some performance

-- 
error compiling committee.c: too many arguments to function