Re: [PATCH 0/3] KVM: Kconfig fixes for the VM-wide private memory attribute

[Sean Christopherson]

On Tue, Oct 20, 2026, Paolo Bonzini wrote:
> A late review of the guest_memfd attributes changes...
> 
> With Linux 7.4 the "private" memory attribute was moved from the VM
> to the individual guest_memfd file descriptor.  The old semantics are
> available for backwards compatibility via CONFIG_KVM_VM_MEMORY_ATTRIBUTES,
> and disabled by default.
> 
> This change has two problems: first, it ties support for VM memory
> attributes entirely to a backwards compatibility symbol for distros.
> Second, it is incompatible with all released versions of QEMU (and
> perhaps most other VMMs?), thus the default is arguably not the
> right one.

I was hoping we could go with a stick approach, but given how painful double-allocating
is, hopefully a carrot will work too. :-)