On Wed, Jul 20, 2022 at 04:08:10PM -0700, Vishal Annapurve wrote:

quoted

quoted

Hmm, so a new slot->arch.page_attr array shouldn't be necessary, KVM can instead
update slot->arch.lpage_info on shared<->private conversions.  Detecting whether
a given range is partially mapped could get nasty if KVM defers tracking to the
backing store, but if KVM itself does the tracking as was previously suggested[*],
then updating lpage_info should be relatively straightfoward, e.g. use
xa_for_each_range() to see if a given 2mb/1gb range is completely covered (fully
shared) or not covered at all (fully private).

[*] https://lore.kernel.org/all/YofeZps9YXgtP3f1@google.com (local)

Yes, slot->arch.page_attr was introduced to help identify whether a page
is completely shared/private at given level. It seems XARRAY can serve
the same purpose, though I know nothing about it. Looking forward to
seeing the patch of using XARRAY.

yes, update slot->arch.lpage_info is good to utilize the existing logic
and Isaku has applied it to slot->arch.lpage_info for 2MB support patches.

Chao, are you planning to implement these changes to ensure proper
handling of hugepages partially mapped as private/shared in subsequent
versions of this series?
Or is this something left to be handled by the architecture specific code?

Ah, the topic gets moved to a different place. I should update here.
There were more discussions under TDX KVM patch series and I actually
just sent out the draft code for this:

https://lkml.org/lkml/2022/7/20/610

That patch is based on UPM v7 here. If I can get more feedbacks there
then I will include an udpated version in UPM v8.

If you have bandwdith, you can also play with that patch, any feedback
is welcome.

Chao

Regards,
Vishal