* [PATCH] vdpa_sim: do not reset IOTLB during device reset
@ 2020-05-14 7:25 Jason Wang
2020-05-14 9:35 ` Michael S. Tsirkin
0 siblings, 1 reply; 3+ messages in thread
From: Jason Wang @ 2020-05-14 7:25 UTC (permalink / raw)
To: mst, jasowang, virtualization, linux-kernel
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>
---
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] vdpa_sim: do not reset IOTLB during device reset
2020-05-14 7:25 [PATCH] vdpa_sim: do not reset IOTLB during device reset Jason Wang
@ 2020-05-14 9:35 ` Michael S. Tsirkin
2020-05-15 3:02 ` Jason Wang
0 siblings, 1 reply; 3+ messages in thread
From: Michael S. Tsirkin @ 2020-05-14 9:35 UTC (permalink / raw)
To: Jason Wang; +Cc: virtualization, linux-kernel
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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] vdpa_sim: do not reset IOTLB during device reset
2020-05-14 9:35 ` Michael S. Tsirkin
@ 2020-05-15 3:02 ` Jason Wang
0 siblings, 0 replies; 3+ messages in thread
From: Jason Wang @ 2020-05-15 3:02 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: virtualization, linux-kernel
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
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-05-15 3:02 UTC | newest]
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2020-05-14 9:35 ` Michael S. Tsirkin
2020-05-15 3:02 ` Jason Wang
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