Re: [PATCH v6 5/9] KVM: guest_memfd: Add helpers to query SHARED vs. PRIVATE for a given page

[Fuad Tabba]

On Thu, 23 Jul 2026 at 22:08, Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Add helpers to check if a given page in a guest_memfd instance is PRIVATE
> versus SHARED, and use the "is shared" helper instead of an open-coded
> equivalent in the user pagefault handler.  In addition to the immediate
> usage, providing an "is private" helper will allow cleaning up the so
> called prepare() code, and eventually will be heavily used once in-place
> conversion support comes along.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Reviewed-by: Fuad Tabba <fuad.tabba@xxxxxxxxx>

Cheers,
/fuad

> ---
>  virt/kvm/guest_memfd.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 2effff582f50..e9d61410e5fb 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -60,6 +60,16 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn)
>         return gfn - slot->base_gfn + slot->gmem.pgoff;
>  }
>
> +static bool kvm_gmem_is_private_mem(struct inode *inode, pgoff_t index)
> +{
> +       return !(GMEM_I(inode)->flags & GUEST_MEMFD_FLAG_INIT_SHARED);
> +}
> +
> +static bool kvm_gmem_is_shared_mem(struct inode *inode, pgoff_t index)
> +{
> +       return !kvm_gmem_is_private_mem(inode, index);
> +}
> +
>  static int __kvm_gmem_prepare_folio(struct kvm *kvm, struct kvm_memory_slot *slot,
>                                     pgoff_t index, struct folio *folio)
>  {
> @@ -397,7 +407,7 @@ static vm_fault_t kvm_gmem_fault_user_mapping(struct vm_fault *vmf)
>         if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
>                 return VM_FAULT_SIGBUS;
>
> -       if (!(GMEM_I(inode)->flags & GUEST_MEMFD_FLAG_INIT_SHARED))
> +       if (!kvm_gmem_is_shared_mem(inode, vmf->pgoff))
>                 return VM_FAULT_SIGBUS;
>
>         folio = kvm_gmem_get_folio(inode, vmf->pgoff);
> --
> 2.55.0.229.g6434b31f56-goog
>