Re: [PATCH 0/8] *** RFC: ARM KVM dirty tracking device ***

Oliver Upton
2024-09-19T09:12:01Z

Hi Lilit,

+cc kvmarm mailing list, get_maintainer is your friend :)

On Wed, Sep 18, 2024 at 03:27:59PM +0000, Lilit Janpoladyan wrote:
> An example of a device that tracks accesses to stage-2 translations and will
> implement page_tracking_device interface is AWS Graviton Page Tracking Agent
> (PTA). We'll be posting code for the Graviton PTA device driver in a separate
> series of patches.

In order to actually review these patches, we need to see an
implementation of such a page tracking device. Otherwise it's hard to
tell that the interface accomplishes the right abstractions.

Beyond that, I have some reservations about maintaining support for
features that cannot actually be tested outside of your own environment.

> When ARM architectural solution (FEAT_HDBSS feature) is available, we intend to
> use it via the same interface most likely with adaptations.

Will the PTA stuff eventually get retired once you get support for FEAT_HDBSS
in hardware?

I think the best way forward here is to implement the architecture, and
hopefully after that your legacy driver can be made to fit the
interface. The FVP implements FEAT_HDBSS, so there's some (slow)
reference hardware to test against.

This is a very interesting feature, so hopefully we can move towards
something workable.

--
Thanks,
Oliver