linux-kernel - Re: [PATCH] vdpa_sim: get rid of DMA ops

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Date:   Sun, 29 Jan 2023 13:47:22 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Stefano Garzarella <sgarzare@...hat.com>, eperezma@...hat.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, xieyongji@...edance.com, hch@....de
Subject: Re: [PATCH] vdpa_sim: get rid of DMA ops

On Fri, Jan 27, 2023 at 6:29 PM Michael S. Tsirkin <mst@...hat.com> wrote:
>
> On Mon, Dec 26, 2022 at 12:12:42PM +0800, Jason Wang wrote:
> > > >@@ -682,6 +553,11 @@ static int vdpasim_dma_unmap(struct vdpa_device *vdpa, unsigned int asid,
> > > >       if (asid >= vdpasim->dev_attr.nas)
> > > >               return -EINVAL;
> > > >
> > > >+      if (vdpasim->iommu_pt[asid]) {
> > >
> > > We are in the vdpasim_dma_unmap, so if vdpasim->iommu_pt[asid] is true,
> > > should be better to return an error, since this case should not happen?
> >
> > So it's a question of how to behave when unmap is called without a
> > map. I think we can leave the code as is or if we wish, it needs a
> > separate patch.
> >
> > (We didn't error this previously anyhow).
> >
> > Thanks
>
> OK I picked as is. Do we want WARN_ON maybe?

This could be triggered by the userspace, so I'm not sure it's worth it.

Thanks

>
> --
> MST
>