On Tue, Jan 17, 2023, Chao Peng wrote:

On Tue, Jan 17, 2023 at 11:21:10AM +0800, Binbin Wu wrote:

quoted

On 12/2/2022 2:13 PM, Chao Peng wrote:

quoted

In confidential computing usages, whether a page is private or shared is
necessary information for KVM to perform operations like page fault
handling, page zapping etc. There are other potential use cases for
per-page memory attributes, e.g. to make memory read-only (or no-exec,
or exec-only, etc.) without having to modify memslots.

Introduce two ioctls (advertised by KVM_CAP_MEMORY_ATTRIBUTES) to allow
userspace to operate on the per-page memory attributes.
   - KVM_SET_MEMORY_ATTRIBUTES to set the per-page memory attributes to
     a guest memory range.
   - KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES to return the KVM supported
     memory attributes.

KVM internally uses xarray to store the per-page memory attributes.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Chao Peng <redacted>
Link: https://lore.kernel.org/all/Y2WB48kD0J4VGynX@google.com/ (local)
---
  Documentation/virt/kvm/api.rst | 63 ++++++++++++++++++++++++++++
  arch/x86/kvm/Kconfig           |  1 +
  include/linux/kvm_host.h       |  3 ++
  include/uapi/linux/kvm.h       | 17 ++++++++

Should the changes introduced in this file also need to be added in
tools/include/uapi/linux/kvm.h ?

Yes I think.

I'm not sure how Paolo or others feel, but my preference is to never update KVM's
uapi headers in tools/ in KVM's tree.  Nothing KVM-related in tools/ actually
relies on the headers being copied into tools/, e.g. KVM selftests pulls KVM's
headers from the .../usr/include/ directory that's populated by `make headers_install`.

Perf's tooling is what actually "needs" the headers to be copied into tools/, so
my preference is to let the tools/perf maintainers deal with the headache of keeping
everything up-to-date.

But I'm hesitate to include in this patch or not. I see many commits sync
kernel kvm.h to tools's copy. Looks that is done periodically and with a
'pull' model.