Re: [PATCH v3 00/16] KVM: arm64: GICv3 ITS emulation

[Christoffer Dall <christoffer.dall@linaro.org>]

On Mon, Mar 14, 2016 at 05:29:44PM +0000, Peter Maydell wrote:
> On 14 March 2016 at 11:13, Andre Przywara <andre.przywara@arm.com> wrote:
> > So I see two ways to fix this:
> > 1.) we find a KVM specific way of letting userland save and restore the
> > ITS tables directly
> > 2.) we implement the BASER<n> registers, but still use our "cache" for
> > normal operations. On demand we would serialize KVM's virtual ITS data
> > structures and put them into the guest's memory, so they could be
> > saved/restored from there.
> 
> I feel like we're rehashing a bunch of design choices we talked
> through way back in the last-but-one Connect. I don't suppose
> anybody wrote down our rationales from back then?

Someone (not me) had the task to write it down, I don't recall if that
happened or not :)

> 
> (In particular I forget whether we decided the ITS tables were
> large enough to need to allow some sort of before-the-VM-stops
> migration of the data, which would be relatively doable with
> option 2 but painful under option 1.)

I think we concluded that it's not so much data that applying dirty
bitmaps stuff on there is strictly necessary, but that being able to do
this was probably a plus, and not very hard to do.

I am quite sure that we dismissed option 1, and were decided on option 2
though.

-Christoffer