Re: [PATCH 1/2] arm: msm: Add System MMU support.

From: Stepan Moskovchenko
Date: Tue Aug 03 2010 - 14:43:55 EST

On 8/3/2010 2:23 AM, Roedel, Joerg wrote:
On Mon, Aug 02, 2010 at 04:29:38PM -0400, Zach Pfeffer wrote:
On Mon, Aug 02, 2010 at 09:58:02AM +0200, Roedel, Joerg wrote:
In the means of the IOMMU-API the domain is the abstraction of an
address space (in other words a page table). The IOMMU(s) which this domain
is later assigned to are determined by the iommu_attach_device calls.
I think the right way to go here is to create the concept of a
device-context in the IOMMU-API and add functions like

iommu_attach_context(struct iommu_domain *domain,
struct iommu_context *ctxt);
iommu_detach_context(struct iommu_context *ctxt);

This would work if you can determine in your iommu-driver which iommu
you need to program for which device. What do you think?

Joerg, I'd like to make sure I understand this. A domain is an address
space separate from the actual page-tables that may be part of an
iommu_context, correct? After I iommu_attach_context the ctxt will
reflect the address space of the domain, correct?
A domain is defined by a single page-table which can be modified using
the iommu_map/iommu_unmap function calls. I am not completly sure what
you mean by an iommu_context. Can you describe what it means in your


I think with some rework, all my use cases can be handled by your existing iommu API. If the domain is treated basically a page table, there will be some changes, but I think it can be done. I will push a new version of my driver in a few days.

One thing that may be helpful for the future, however, is maybe something like adding iommu_tlb_flush to the ops. I suppose this would either have to take a device, or the domain would need to keep a list of devices it had been attached to (so that their TLBs can be invalidated). But I suppose on the other hand, iommu_map/unmap may be able to just implicitly invalidate the TLB also, since TLB invalidation often follows map/unmap. What are your thoughts?

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