linux-kernel - Re: [PATCH v8] KVM: PPC: reserve a capability and ioctl numbers for realmode VFIO

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Date:	Wed, 28 Aug 2013 09:38:03 +0300
From:	Gleb Natapov <gleb@...hat.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	linuxppc-dev@...ts.ozlabs.org,
	David Gibson <david@...son.dropbear.id.au>,
	Paul Mackerras <paulus@...ba.org>, kvm@...r.kernel.org,
	Alexander Graf <agraf@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8] KVM: PPC: reserve a capability and ioctl numbers for
 realmode VFIO

On Wed, Aug 28, 2013 at 11:26:31AM +1000, Benjamin Herrenschmidt wrote:
> On Wed, 2013-08-28 at 10:51 +1000, Alexey Kardashevskiy wrote:
> > The ioctl I made up is basically a copy of KVM_CREATE_SPAPR_TCE which does
> > the same thing for emulated devices and it is there for quite a while but
> > it is not really extensible. And these two ioctls share some bits of code.
> > Now we will have 2 pieces of code which do almost the same thing but in a
> > different way. Kinda sucks :(
> 
> Right. Thus the question, Gleb, we can either:
> 
>  - Keep Alexey patch as-is allowing us to *finally* merge that stuff
> that's been around for monthes
> 
>  - Convert *both* existing TCE objects to the new 
> KVM_CREATE_DEVICE, and have some backward compat code for the old one.
> 
> I don't think it makes sense to have the "emulated TCE" and "IOMMU TCE"
> objects use a fundamentally different API and infrastructure.
> 
As a general rule we are not going to mandate converting old devices to
new API, but if it make sense to do here I would much prefer that over
adding another special ioctl

> > >> So my stuff is not going to upstream again. Heh. Ok. I'll implement it.
> > >>
> > > Thanks! Should I keep KVM_CAP_SPAPR_MULTITCE capability patch or can I
> > > drop it for now?
> > 
> > Please keep it, it is unrelated to the IOMMU-VFIO thing.
> 

--
			Gleb.
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