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Date: Fri, 20 May 2011 12:28:44 +0300
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] [RFC v1] Add declarations for hierarchical memory
	region API
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org

On 05/20/2011 12:11 AM, Stefan Hajnoczi wrote:
> On Thu, May 19, 2011 at 3:12 PM, Avi Kivity<avi@redhat.com>  wrote:
> >  +struct MemoryRegion {
> >  +    /* All fields are private - violators will be prosecuted */
> >  +    const MemoryRegionOps *ops;
> >  +    MemoryRegion *parent;
>
> In the case where a region is aliased (mapped twice into the address
> space at different addresses) I need two MemoryRegions?

Yes.

> The
> MemoryRegion describes an actual mapping in the<parent, addr,
> ram_addr>  tuple, not just the attributes of the region (ops, size,
> ...).

Correct.  The region is not just a read-only descriptor.  
memory_region_add_subregion() can be used only once on a region (unless 
you _del_subregion() in between).

(it also follows from the fact that there is no separate opaque for 
registration, and from the fact that RAM is owned by the region, not 
provided as part of registration).

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.