Re: [PATCH v3 04/70] HostMem: Add mechanism to opt in kvm guest memfd via MachineState

[David Hildenbrand]

On 16.11.23 03:53, Xiaoyao Li wrote:
> On 11/16/2023 2:14 AM, David Hildenbrand wrote:
> > On 15.11.23 08:14, Xiaoyao Li wrote:
> > > Add a new member "require_guest_memfd" to memory backends. When it's set
> > > to true, it enables RAM_GUEST_MEMFD in ram_flags, thus private kvm
> > > guest_memfd will be allocated during RAMBlock allocation.
> > >
> > > Memory backend's @require_guest_memfd is wired with @require_guest_memfd
> > > field of MachineState. MachineState::require_guest_memfd is supposed to
> > > be set by any VMs that requires KVM guest memfd as private memory, e.g.,
> > > TDX VM.
> > >
> > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> >
> > I'm confused, why do we need this if it's going to be the same for all
> > memory backends right now?
>
> I want to provide a elegant (in my sense) way to configure "the need of
> guest memfd" instead of checking x86machinestate->vm_type in physmem.c

It's suboptimal right now, but I guess you want to avoid looking up the 
machine e.g., in ram_backend_memory_alloc().

I'd suggest s/require_guest_memfd/guest_memfd/gc in "struct 
HostMemoryBackend".

Apart from that LGTM.

--
Cheers,

David / dhildenb