On 2020/5/14 下午5:35, Michael S. Tsirkin wrote:
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@xxxxxxxxxx>
That's a bit weird, and can be a security risk if state
leaks between security domains through this.
I'm not sure I get this. Note that:
1) For devices that depend on platform IOMMU, the mappings are valid
across device reset
2) vhost_vdpa will reset IOTLB during release, so I think there's no
security leak in this case
If we reset IOTLB during device reset, there will be an inconsistency
between on-chip IOMMU devices and platform IOMMU devices. We can fix
this inconsistency in another way, e.g unmap during vhost_vdpa_reset.
This means userspace need to replay the mapping before DRIVER_OK, which
seems a burden to userspace.
And there's 0 chance any hardware implementation can
keep the translations around across resets - there
is simply nowhere to keep them.
It depends on the hardware implementation, e.g the IOMMU does not belong
to VF but PF.
Thanks
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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