From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 12/13] kvm/powerpc: Accelerate H_PUT_TCE by
 implementing it in real mode
Date: Tue, 17 May 2011 19:11:50 +1000
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Cc: Paul Mackerras <paulus@samba.org>, linuxppc-dev@ozlabs.org,
	kvm@vger.kernel.org
To: Alexander Graf <agraf@suse.de>
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On Tue, 2011-05-17 at 10:01 +0200, Alexander Graf wrote:
> I'm not sure I fully understand how this is supposed to work. If the
> tables are kept inside the kernel, how does userspace get to know
> where to DMA to?

The guest gets a dma range from the device-tree which is the range of
device-side dma addresses it can use that correspond to the table.

The guest kernel uses the normal linux iommu space allocator to allocate
space in that region and uses H_PUT_TCE to populate the corresponding
table entries.

This is the same interface that is used for "real" iommu's with PCI
devices btw.

Cheers,
Ben.