[Xen-devel] Re: save/restore dev in HV

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 22/1/07 2:44 am, "Zhai, Edwin" <edwin.zhai@xxxxxxxxx> wrote:

> 1. it put more responsibility on developer to maintain the format/alignment of
> hw status struct.

This is true. We now have anough script support for CONFIG_COMPAT that we
could probably check all save structs for 32-on-64 compatibility
automatically.

> 2. compatibility issue. e.g. adding a new field in middle of the hw struct
> would break restoring an old image.

We wouldn't do this -- we'd define a new structure, or add new fields at the
end in a backward compatible way.

The code as it is is *not* finished by the way, and so gives a slightly poor
impression of this approach. The aim is to have some of the structures
broken down into more chunks: so for example the hvm_irq structure will move
back to where it came from (a private header file) and instead we will have
descriptor chunks for PCI INTx wire state, ISA IRQ wire state, and PCI-ISA
link state -- note that each of these will effectively be an array which
will be easily extended (or shrunk) if e.g., we add another PCI bus.

This is the hard bit -- auditing every chunk, deciding if it contains
redundant info, or info that is only an artefact of the crrent device-model
implementation, or whether the chunk needs to be broken into more pieces to
maintain better logical grouping and extensibility.

 -- Keir



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