Re: [PATCH 2/6] i915/gvt/kvm: a NULL ->mm does not mean a thread is a kthread

[Christoph Hellwig]

On Mon, Apr 06, 2020 at 11:08:46PM -0400, Yan Zhao wrote:
> hi
> we were removing this code. see
> https://lore.kernel.org/kvm/20200313031109.7989-1-yan.y.zhao@xxxxxxxxx/

This didn't make 5.7-rc1.

> The implementation of vfio_dma_rw() has been in vfio next tree.
> https://github.com/awilliam/linux-vfio/commit/8d46c0cca5f4dc0538173d62cd36b1119b5105bc


This made 5.7-rc1, so I'll update the series to take it into account.

T
> in vfio_dma_rw(),  we still use
> bool kthread = current->mm == NULL.
> because if current->mm != NULL and current->flags & PF_KTHREAD, instead
> of calling use_mm(), we first check if (current->mm == mm) and allow copy_to_user() if it's true.
> 
> Do you think it's all right?

I can't think of another way for a kernel thread to have a mm indeed.