On Sat, Jan 14, 2023 at 12:37:59AM +0000, Sean Christopherson wrote:

On Fri, Dec 02, 2022, Chao Peng wrote:

quoted

This patch series implements KVM guest private memory for confidential
computing scenarios like Intel TDX[1]. If a TDX host accesses
TDX-protected guest memory, machine check can happen which can further
crash the running host system, this is terrible for multi-tenant
configurations. The host accesses include those from KVM userspace like
QEMU. This series addresses KVM userspace induced crash by introducing
new mm and KVM interfaces so KVM userspace can still manage guest memory
via a fd-based approach, but it can never access the guest memory
content.

The patch series touches both core mm and KVM code. I appreciate
Andrew/Hugh and Paolo/Sean can review and pick these patches. Any other
reviews are always welcome.
  - 01: mm change, target for mm tree
  - 02-09: KVM change, target for KVM tree

A version with all of my feedback, plus reworked versions of Vishal's selftest,
is available here:

  git@github.com:sean-jc/linux.git x86/upm_base_support

It compiles and passes the selftest, but it's otherwise barely tested.  There are
a few todos (2 I think?) and many of the commits need changelogs, i.e. it's still
a WIP.

Thanks very much for doing this. Almost all of your comments are well
received, except for two cases that need more discussions which have
replied individually.

As for next steps, can you (handwaving all of the TDX folks) take a look at what
I pushed and see if there's anything horrifically broken, and that it still works
for TDX?

I have integrated this into my local TDX repo, with some changes (as I
replied individually), the new code basically still works with TDX.

I have also asked other TDX folks to take a look.

Fuad (and pKVM folks) same ask for you with respect to pKVM.  Absolutely no rush
(and I mean that).

On my side, the two things on my mind are (a) tests and (b) downstream dependencies
(SEV and TDX).  For tests, I want to build a lists of tests that are required for
merging so that the criteria for merging are clear, and so that if the list is large
(haven't thought much yet), the work of writing and running tests can be distributed.

Regarding downstream dependencies, before this lands, I want to pull in all the
TDX and SNP series and see how everything fits together.  Specifically, I want to
make sure that we don't end up with a uAPI that necessitates ugly code, and that we
don't miss an opportunity to make things simpler.  The patches in the SNP series to
add "legacy" SEV support for UPM in particular made me slightly rethink some minor
details.  Nothing remotely major, but something that needs attention since it'll
be uAPI.

I'm off Monday, so it'll be at least Tuesday before I make any more progress on
my side.

Appreciate your effort. As for the next steps, if you see something we
can do parallel, feel free to let me know.

Thanks,
Chao