Add kvm->file as a no-reference back-pointer to the VM file in struct kvm. The pointer is set at VM creation time and cleared under WRITE_ONCE() in kvm_vm_release() before the file is freed. Callers storing the file must take their own reference. Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson Signed-off-by: Steffen Eiden --- include/linux/kvm_host.h | 6 ++++++ virt/kvm/kvm_main.c | 4 ++++ 2 files changed, 10 insertions(+) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index a1bf6d4a8f46..2b56fb4e8555 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -784,6 +784,12 @@ struct kvm { * kvm_swap_active_memslots(). */ struct mutex slots_arch_lock; + /* + * Back-reference to the VM file for subsystems (e.g., VFIO). Holds no + * reference to avoid pinning the VM. Callers storing the file must + * take their own reference. + */ + struct file *file; struct mm_struct *mm; /* userspace tied to this vm */ unsigned long nr_memslot_pages; /* The two memslot sets - active and inactive (per address space) */ diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 0172ca94f82e..bab71d398236 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1352,6 +1352,8 @@ static int kvm_vm_release(struct inode *inode, struct file *filp) kvm_irqfd_release(kvm); + WRITE_ONCE(kvm->file, NULL); + kvm_put_kvm(kvm); return 0; } @@ -5532,6 +5534,8 @@ static int kvm_dev_ioctl_create_vm(unsigned long type) goto put_kvm; } + kvm->file = file; + /* * Don't call kvm_put_kvm anymore at this point; file->f_op is * already set, with ->release() being kvm_vm_release(). In error -- 2.53.0