Re: [PATCH 4/6] kvm-userland.git mmu notifier compat

Avi Kivity
2008-07-29T13:30:44Z

Andrea Arcangeli wrote:
> On Tue, Jul 29, 2008 at 03:49:08PM +0300, Avi Kivity wrote:
>
>> Applied; thanks. I think page pinning can be worked around by pinning all
>> pages on memslot registration (and unpinning on memslot removal); this will
>> slow down virtual machine startup, but is at least simple.
>>
>
> This has the benefit that will also fix the tlb issues, but if we go
> this way if a sles/rhel user takes the next kvm release, all ram will
> be pinned and it won't swap anything for him, like with my patch that
> added VM_LOCKED. Said that swap wasn't a reliable feature before so
> nobody should have depended on that.
>

A 64-bit guest would pin all pages anyway as soon as it touched them the
first time, through the direct map.

> If we really go this memslot-wide-pinning way I could submit to rhel
> and sles a mmu notifier backport so the rhel/sles users won't have to
> wait to get their kernel upgraded to 2.6.27 to get full kvm-paging.
>

I really doubt they would take it; Red Hat will want to point people at
ovirt and Novel at Xen.

It's not a simple patch.

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