Re: [PATCH v9 01/41] KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings

[Sean Christopherson]

On Fri, Jul 31, 2026, Xiaoyao Li wrote:
> On 7/29/2026 8:35 AM, Ackerley Tng via B4 Relay wrote:
> > From: Sean Christopherson<seanjc@xxxxxxxxxx>
> > 
> > Start plumbing in guest_memfd support for in-place private<=>shared
> > conversions by tracking attributes via a maple tree.  KVM currently tracks
> > private vs. shared attributes on a per-VM basis, which made sense when a
> > guest_memfd_only_ supported private memory, but tracking per-VM simply
> > can't work for in-place conversions as the shared/private status of a given
> > page needs to be per-gmem_inode, not per-VM.
> > 
> > Use the filemap invalidation lock to protect the maple tree, as taking the
> > lock for read when faulting in memory (for userspace or the guest) isn't
> > expected to result in meaningful contention, and using a separate lock
> > would add significant complexity (avoiding deadlock is quite difficult).
> > 
> > Co-developed-by: Vishal Annapurve<vannapurve@xxxxxxxxxx>
> > Signed-off-by: Vishal Annapurve<vannapurve@xxxxxxxxxx>
> > Co-developed-by: Fuad Tabba<tabba@xxxxxxxxxx>
> > Signed-off-by: Fuad Tabba<tabba@xxxxxxxxxx>
> > Signed-off-by: Sean Christopherson<seanjc@xxxxxxxxxx>
> > Tested-by: Shivank Garg<shivankg@xxxxxxx>
> > Co-developed-by: Ackerley Tng<ackerleytng@xxxxxxxxxx>
> > Signed-off-by: Ackerley Tng<ackerleytng@xxxxxxxxxx>
> 
> Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> 
> <...>
> 
> >   static __always_inline struct gmem_inode *GMEM_I(struct inode *inode)
> > @@ -60,9 +68,25 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn)
> >   	return gfn - slot->base_gfn + slot->gmem.pgoff;
> >   }
> > +static u64 kvm_gmem_interpret_entry(struct inode *inode, void *entry)
> 
> Ummm, I'm not sure on the name. It doesn't look like KVM's style?
> 
> Maybe, just kvm_gmem_get_attributes()?

+1000, "interpret_entry" is extremely vague.