On Fri, Jun 26, 2026, Yan Zhao wrote:

On Thu, Jun 25, 2026 at 07:36:28AM -0700, Sean Christopherson wrote:

quoted

On Thu, Jun 25, 2026, Yan Zhao wrote:
And I'm not remotely convinced that prepending allow_ to the param will help
end users diagnose "unexpected" memory consumption, in quotes because anyone that
is deploying a stack that utilizes out-of-place conversion absolutely needs to
understand and plan for the additional memory consumption.  I.e. if the memory
consumption is "unexpected" to the end user, they likely have far bigger problems.

My first impression of gmem_in_place_conversion=true was that it enforces gmem
in-place conversion. However, it actually only enforces per-gmem private/shared
attribute.
My worry was that people might think it's a kernel bug if userspace can still
have shared memory from other sources after they configured
gmem_in_place_conversion=true.

Ah, I see where you're coming from.  FWIW, truly enforcing in-place conversion
is flat out impossible.  E.g. userspace can simply replace the memslot, at which
point the memory effectively reverts to shared.

However, I have no strong opinion if you think gmem_in_place_conversion is good,
and with the above documentation. :)

Ya, I think this largely a documentation problem.  I agree that a param name
like gmem_private_memory_attributes would be more precise, but I think it'd be
far less informative for the vast majority of users that only care whether or
not KVM can do in-place conversion, and don't care about how that is done.