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SubjectRe: [PATCH] vdpa_sim: do not reset IOTLB during device reset
On Thu, May 14, 2020 at 03:25:49PM +0800, Jason Wang wrote:
> We reset IOTLB during device reset this breaks the assumption that the
> mapping needs to be controlled via vDPA DMA ops explicitly in a
> incremental way. So the networking will be broken after e.g a guest
> reset.
>
> Fix this by not resetting the IOTLB during device reset.
>
> Signed-off-by: Jason Wang <jasowang@redhat.com>


That's a bit weird, and can be a security risk if state
leaks between security domains through this.
And there's 0 chance any hardware implementation can
keep the translations around across resets - there
is simply nowhere to keep them.

IMHO we need a different way to make this work, simulator
needs to look like a hardware device as much as possible.


> ---
> drivers/vdpa/vdpa_sim/vdpa_sim.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> index 7957d2d41fc4..cc5525743a25 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> @@ -119,8 +119,6 @@ static void vdpasim_reset(struct vdpasim *vdpasim)
> for (i = 0; i < VDPASIM_VQ_NUM; i++)
> vdpasim_vq_reset(&vdpasim->vqs[i]);
>
> - vhost_iotlb_reset(vdpasim->iommu);
> -
> vdpasim->features = 0;
> vdpasim->status = 0;
> ++vdpasim->generation;
> --
> 2.20.1

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