[Intel-gfx] [PATCH v1 1/5] iommufd: Create access in vfio_iommufd_emulated_bind()

[Nicolin Chen]

On Thu, Mar 16, 2023 at 05:38:41AM +0000, Tian, Kevin wrote:
> External email: Use caution opening links or attachments
> 
> 
> > From: Nicolin Chen <nicolinc at nvidia.com>
> > Sent: Thursday, March 16, 2023 1:33 PM
> >
> > Hi Kevin,
> >
> > I've fixed the other two commits. Here is the one that I am
> > not sure about:
> >
> > On Thu, Mar 16, 2023 at 02:53:50AM +0000, Tian, Kevin wrote:
> >
> > > > [2] This adds iommufd_access_detach() in the cdev series:
> > > >     "iommufd/device: Add iommufd_access_detach() API"
> > > >
> > > >
> > https://github.com/nicolinc/iommufd/commit/4110522146ca1fc0d5321c04a
> > > > 097e2c9d9e26af4
> > >
> > > also add a check if old_ioas exists it must equal to the new_ioas in attach.
> >
> > This is the commit adding detach(). And there's a check in it:
> >       if (WARN_ON(!access->ioas))
> >
> > Do you mean having an "if (access->ioas) return -EBUSY;" line
> > in the commit adding attach()?
> 
> if (access->ioas && access->ioas != new_ioas)
>         return -EBUSY;
> 
> yes this is for attach.

OK. For attach(), the access->ioas shouldn't be !NULL, I think.
At the point of adding attach(), the uAPI doesn't support the
replacement use case yet. And later we have a separate API for
that.

So I think it'd be just:
	if (access->ioas)
		return -EBUSY;

The reason why I didn't add it is actually because the caller
vfio_iommufd_emulated_attach_ioas() has a check of "attached"
already. Yet, it doesn't hurt to have one more in the API.

Thanks
Nic