On Tue, Jan 24, 2023 at 01:27:50AM +0000, Sean Christopherson wrote:

On Thu, Jan 19, 2023, Isaku Yamahata wrote:

quoted

On Thu, Jan 19, 2023 at 03:25:08PM +0000,
Sean Christopherson [off-list ref] wrote:

quoted

On Thu, Jan 19, 2023, Isaku Yamahata wrote:

quoted

On Sat, Jan 14, 2023 at 12:37:59AM +0000,
Sean Christopherson [off-list ref] wrote:

quoted

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.

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?

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.

Although I'm still debuging with TDX KVM, I needed the following.
kvm_faultin_pfn() is called without mmu_lock held.  the race to change
private/shared is handled by mmu_seq.  Maybe dedicated function only for
kvm_faultin_pfn().

Gah, you're not on the other thread where this was discussed[*].  Simply deleting
the lockdep assertion is safe, for guest types that rely on the attributes to
define shared vs. private, KVM rechecks the attributes under the protection of
mmu_seq.

I'll get a fixed version pushed out today.

[*] https://lore.kernel.org/all/Y8gpl+LwSuSgBFks@google.com (local)

Now I have tdx kvm working. I've uploaded at the followings.
It's rebased to v6.2-rc3.
        git@github.com:yamahata/linux.git tdx/upm
        git@github.com:yamahata/qemu.git tdx/upm

And I finally got a working, building version updated and pushed out (again to):

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

Took longer than expected to get the memslot restrictions sussed out.  I'm done
working on the code for now, my plan is to come back to it+TDX+SNP in 2-3 weeks
to resolves any remaining todos (that no one else tackles) and to do the whole
"merge the world" excersise.

quoted

kvm_mmu_do_page_fault() needs the following change.
kvm_mem_is_private() queries mem_attr_array.  kvm_faultin_pfn() also uses
kvm_mem_is_private(). So the shared-private check in kvm_faultin_pfn() doesn't
make sense. This change would belong to TDX KVM patches, though.

Yeah, SNP needs similar treatment.  Sorting that out is high up on the todo list.

Hi Sean,

We've rebased the SEV+SNP support onto your updated UPM base support
tree and things seem to be working okay, but we needed some fixups on
top of the base support get things working, along with 1 workaround
for an issue that hasn't been root-caused yet:

  https://github.com/mdroth/linux/commits/upmv10b-host-snp-v8-wip

  *stash (upm_base_support): mm: restrictedmem: Kirill's pinning implementation
  *workaround (use_base_support): mm: restrictedmem: loosen exclusivity check
  *fixup (upm_base_support): KVM: use inclusive ranges for restrictedmem binding/unbinding
  *fixup (upm_base_support): mm: restrictedmem: use inclusive ranges for issuing invalidations
  *fixup (upm_base_support): KVM: fix restrictedmem GFN range calculations
  *fixup (upm_base_support): KVM: selftests: CoCo compilation fixes

We plan to post an updated RFC for v8 soon, but also wanted to share
the staging tree in case you end up looking at the UPM integration aspects
before then.

-Mike