Re: [Xen-devel] [PATCH v8 for-4.9 1/5] hvm/dmop: Box dmop_args rather than passing multiple parameters around

[Julien Grall <julien.grall@xxxxxxx>]

On 21/04/17 15:44, Jennifer Herbert wrote:
> Hi Julien,
Hello Jenny,

> This is extending an existing feature.
> Once 4.9 is released, the existing feature will be frozen, and the only
> way to later get the
> extra functionality would be to created a completely new dm_op, which
> does something very similar
> to an existing one.  Although not the end of the world, this wouldnt
> look so nice.
>
> The benefits of the feature are that a VM can request multiple extents
> to be marked as modified at once,
> without having to loop though them, calling the existing call many many
> times.  This will be more efficient and faster.
> As an extra, additional accessors have been created for dm_op
> operations, which new dm_ops can take advantage of.
>
> The benefits of introducing the feature for 4.9 as opposed to later is
> that we wont' have to support the same feature, with multiple dm_opts
> with varying parameters - which as well as looking less good, also
> unnesseserily bloats the code.
>
> I think risks are low, with a minor, affecting dm_op operations only.
> The core change, in 5/5 will only affect the modified memory call, which
> has been tested.  The remaining patches are to tidy up and fix existing
> behaviour.
It would have been useful to have a cover letter explaining that.

Anyway, I think I agree it would be better to get the DM OP ABI in shape 
for continuability before it gets stable. Although, it would be nice if 
we can get that done in early RCs.
Release-acked-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,

--
Julien Grall

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