linux-kernel - Re: [PATCH 3/4] KVM: PPC: Add support for IOMMU in-kernel handling

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Message-ID: <1371943693.3944.104.camel@pasglop>
Date:	Sun, 23 Jun 2013 09:28:13 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Gibson <david@...son.dropbear.id.au>
Cc:	Alex Williamson <alex.williamson@...hat.com>,
	Alexey Kardashevskiy <aik@...abs.ru>,
	Alexander Graf <agraf@...e.de>, linuxppc-dev@...ts.ozlabs.org,
	Paul Mackerras <paulus@...ba.org>,
	"kvm@...r.kernel.org mailing list" <kvm@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	kvm-ppc@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>,
	Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH 3/4] KVM: PPC: Add support for IOMMU in-kernel handling

On Sat, 2013-06-22 at 22:03 +1000, David Gibson wrote:
> I think the interface should not take the group fd, but the container
> fd.  Holding a reference to *that* would keep the necessary things
> around.  But more to the point, it's the right thing semantically:
> 
> The container is essentially the handle on a host iommu address space,
> and so that's what should be bound by the KVM call to a particular
> guest iommu address space.  e.g. it would make no sense to bind two
> different groups to different guest iommu address spaces, if they were
> in the same container - the guest thinks they are different spaces,
> but if they're in the same container they must be the same space.

Interestingly, how are we going to extend that when/if we implement
DDW ?

DDW means an API by which the guest can request the creation of
additional iommus for a given device (typically, in addition to the
default smallish 32-bit one using 4k pages, the guest can request
a larger window in 64-bit space using a larger page size).

Cheers,
Ben.


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