Re: [PATCH v13 16/35] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory

[Sean Christopherson]

On Thu, Nov 02, 2023, Fuad Tabba wrote:
> On Wed, Nov 1, 2023 at 9:55 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> > E.g. a misbehaving userspace could prematurely delete a memslot.  And the more
> > fun example is intrahost migration, where the plan is to allow pointing multiple
> > guest_memfd files at a single guest_memfd inode:
> > https://lore.kernel.org/all/cover.1691446946.git.ackerleytng@xxxxxxxxxx
> >
> > There was a lot of discussion for this, but it's scattered all over the place.
> > The TL;DR is is that the inode will represent physical memory, and a file will
> > represent a given "struct kvm" instance's view of that memory.  And so the memory
> > isn't reclaimed until the inode is truncated/punched.
> >
> > I _think_ this reflects the most recent plan from the guest_memfd side:
> > https://lore.kernel.org/all/1233d749211c08d51f9ca5d427938d47f008af1f.1689893403.git.isaku.yamahata@xxxxxxxxx

Doh, sitting in my TODO folder...

https://lore.kernel.org/all/20231016115028.996656-1-michael.roth@xxxxxxx

> Thanks for pointing that out. I think this might be the way to go.
> I'll have a closer look at this and see how to get it to work with
> pKVM.