Re: [Xen-devel] [PATCH v3 5/6] xen: record physmap changes to xenstore

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 25 Jan 2012, Avi Kivity wrote:
> On 01/19/2012 04:16 PM, Stefano Stabellini wrote:
> > > 
> > > If you are migrating to a newer qemu then the <original-addr> could in
> > > principal change, I think.
> >
> > Not unless the implementation of qemu_ram_alloc_from_ptr or
> > find_ram_offset change, but these are core qemu functions.
> 
> Both of these functions will be removed.  There will no longer be a
> qemu-internal address space for physical memory; instead memory will be
> addressed using a (MemoryRegion, offset) pair.
> 
> We can/will hook memory_region_init_ram() to call xen_ram_alloc() which
> can then generate those old addresses, but those (like qemu_ram_alloc())
> are dependent on allocation order and you shouldn't depend on them
> returning stable values.
> 
> > Or the device starts allocating more memory of course, but it wouldn't
> > be the same device anymore.
> > In any case, if we also match on the MemoryRegion name we cannot go
> > wrong.
> 
> Match on just the MemoryRegion (and match on the object itself, not the
> name; see xen_register_framebuffer()).

I agree that would be ideal, but how can that work across save/restore?
Unless we introduce some other kind of identifier for MemoryRegion, the
best we have is the name right now, correct?

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