Messages in this thread | | | Subject | Re: [PATCH] vdpa_sim: do not reset IOTLB during device reset | From | Jason Wang <> | Date | Fri, 15 May 2020 11:02:00 +0800 |
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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@redhat.com> > > 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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