On Mon, 6 Jul 2020 16:04:13 +0200 Markus Elfring wrote: > > Can another design approach make sense here? > > + bool thread_use_mm = ((current->flags & PF_KTHREAD) && !current->mm); > + if (thread_use_mm)
Good. See below. > > > > kthread_use_mm(mm); --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -2798,7 +2798,7 @@ static int vfio_iommu_type1_dma_rw_chunk struct mm_struct *mm; unsigned long vaddr; struct vfio_dma *dma; - bool kthread = current->mm == NULL; + bool kthread_load_mm; size_t offset; *copied = 0; @@ -2812,11 +2812,12 @@ static int vfio_iommu_type1_dma_rw_chunk return -EPERM; mm = get_task_mm(dma->task); - if (!mm) return -EPERM; - if (kthread) + kthread_load_mm = current->flags & PF_KTHREAD && + current->mm == NULL; + if (kthread_load_mm) kthread_use_mm(mm); else if (current->mm != mm) goto out; @@ -2843,7 +2844,7 @@ static int vfio_iommu_type1_dma_rw_chunk } else *copied = copy_from_user(data, (void __user *)vaddr, count) ? 0 : count; - if (kthread) + if (kthread_load_mm) kthread_unuse_mm(mm); out: mmput(mm); _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu