Re: [RFC PATCH v4 01/13] iommu: Introduce dirty log tracking framework

[Lu Baolu]

Hi keqian,

On 5/12/21 4:44 PM, Keqian Zhu wrote:
> On 2021/5/12 11:20, Lu Baolu wrote:
> > On 5/11/21 3:40 PM, Keqian Zhu wrote:
> > > > For upper layers, before starting page tracking, they check the
> > > > dirty_page_trackable attribution of the domain and start it only it's
> > > > capable. Once the page tracking is switched on the vendor iommu driver
> > > > (or iommu core) should block further device attach/detach operations
> > > > until page tracking is stopped.
> > > But when a domain becomes capable after detaching a device, the upper layer
> > > still needs to query it and enable dirty log for it...
> > >
> > > To make things coordinated, maybe the upper layer can register a notifier,
> > > when the domain's capability change, the upper layer do not need to query, instead
> > > they just need to realize a callback, and do their specific policy in the callback.
> > > What do you think?
> >
> > That might be an option. But why not checking domain's attribution every
> > time a new tracking period is about to start?
> Hi Baolu,
>
> I'll add an attribution in iommu_domain, and the vendor iommu driver will update
> the attribution when attach/detach devices.
>
> The attribute should be protected by a lock, so the upper layer shouldn't access
> the attribute directly. Then the iommu_domain_support_dirty_log() still should be
> retained. Does this design looks good to you?

Yes, that's what I was thinking of. But I am not sure whether it worth
of a lock here. It seems not to be a valid behavior for upper layer to
attach or detach any device while doing the dirty page tracking.

Best regards,
baolu