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

[Xiaoyao Li]

On 11/20/2023 5:30 PM, David Hildenbrand wrote:
> 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".

sure!

> Apart from that LGTM.