Hi Patrick, On Tue, Jul 9, 2024 at 2:21 PM Patrick Roy <roypat@xxxxxxxxxxxx> wrote: > > Allow mapping guest_memfd into userspace. Since AS_INACCESSIBLE is set > on the underlying address_space struct, no GUP of guest_memfd will be > possible. This patch allows mapping guest_memfd() unconditionally. Even if it's not guppable, there are other reasons why you wouldn't want to allow this. Maybe a config flag to gate it? e.g., https://lore.kernel.org/all/20240222161047.402609-4-tabba@xxxxxxxxxx/ > > Signed-off-by: Patrick Roy <roypat@xxxxxxxxxxxx> > --- > virt/kvm/guest_memfd.c | 31 ++++++++++++++++++++++++++++++- > 1 file changed, 30 insertions(+), 1 deletion(-) > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index dc9b0c2d0b0e..101ec2b248bf 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -319,7 +319,37 @@ static inline struct file *kvm_gmem_get_file(struct kvm_memory_slot *slot) > return get_file_active(&slot->gmem.file); > } > > +static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf) > +{ > + struct folio *folio; > + > + folio = kvm_gmem_get_folio(file_inode(vmf->vma->vm_file), vmf->pgoff, true); > + > + if (!folio) > + return VM_FAULT_SIGBUS; > + > + vmf->page = folio_file_page(folio, vmf->pgoff); > + > + return VM_FAULT_LOCKED; > +} > + > +static const struct vm_operations_struct kvm_gmem_vm_ops = { > + .fault = kvm_gmem_fault > +}; > + > +static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) > +{ > + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) > + return -EINVAL; > + > + vm_flags_set(vma, VM_DONTDUMP); > + vma->vm_ops = &kvm_gmem_vm_ops; > + > + return 0; > +} > + > static struct file_operations kvm_gmem_fops = { > + .mmap = kvm_gmem_mmap, > .open = generic_file_open, > .release = kvm_gmem_release, > .fallocate = kvm_gmem_fallocate, > @@ -594,7 +624,6 @@ static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot, > return -EFAULT; > } > > - gmem = file->private_data; Is this intentional? Cheers, /fuad > if (xa_load(&gmem->bindings, index) != slot) { > WARN_ON_ONCE(xa_load(&gmem->bindings, index)); > return -EIO; > -- > 2.45.2 >
