linux-kernel - Re: [PATCH 8/8] KVM: PPC: Add hugepage support for IOMMU in-kernel handling

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Date:	Thu, 11 Jul 2013 22:37:13 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Alexander Graf <agraf@...e.de>
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	linuxppc-dev@...ts.ozlabs.org,
	David Gibson <david@...son.dropbear.id.au>,
	Paul Mackerras <paulus@...ba.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	kvm-ppc@...r.kernel.org
Subject: Re: [PATCH 8/8] KVM: PPC: Add hugepage support for IOMMU in-kernel
 handling

On Thu, 2013-07-11 at 11:52 +0200, Alexander Graf wrote:
> > Where exactly (it is rather SPAPR_TCE_IOMMU but does not really
> matter)?
> > Select it on KVM_BOOK3S_64? CONFIG_KVM_BOOK3S_64_HV?
> > CONFIG_KVM_BOOK3S_64_PR? PPC_BOOK3S_64?
> 
> I'd say the most logical choice would be to check the Makefile and see
> when it gets compiled. For those cases we want it enabled.

What *what* gets compiled ? You know our Makefile, it's crap :-)

We enable built-in things when CONFIG_KVM=m (which means you cannot take
a kernel build with CONFIG_KVM not set, enable CONFIG_KVM=m, and just
build the module, it won't work).

We could use KVM_BOOK3S_64 maybe ?

> > I am trying to imagine a configuration where we really do not want
> > IOMMU_API. Ben mentioned PPC32 and embedded PPC64 and that's it so
> any of
> > BOOK3S (KVM_BOOK3S_64 is the best) should be fine, no?
> 
> book3s_32 doesn't want this, but any book3s_64 implementation could
> potentially use it, yes. That's pretty much what the Makefile tells
> you too :).

Not really no. But that would do. You could have give a more useful
answer in the first place though rather than stringing him along.

Cheers,
Ben.


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