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 at redhat.com> --- 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
Michael S. Tsirkin
2020-May-14 09:35 UTC
[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 at 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
On 2020/5/14 ??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 at 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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