2023-04-15 02:37:46

by Cindy Lu

Subject: [PATCH v2] vhost_vdpa: fix unmap process in no-batch mode

While using the no-batch mode with vIOMMU enabled
Qemu will call a large memory to unmap. Much larger than the memory
mapped to the kernel. The iotlb is NULL in the kernel and will return fail.
Which causes failure.
To fix this, we will not remove the AS while the iotlb->nmaps is 0.
This will free in the vhost_vdpa_clean

Signed-off-by: Cindy Lu <[email protected]>
---
drivers/vhost/vdpa.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 7be9d9d8f01c..74c7d1f978b7 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -851,11 +851,7 @@ static void vhost_vdpa_unmap(struct vhost_vdpa *v,
if (!v->in_batch)
ops->set_map(vdpa, asid, iotlb);
}
- /* If we are in the middle of batch processing, delay the free
- * of AS until BATCH_END.
- */
- if (!v->in_batch && !iotlb->nmaps)
- vhost_vdpa_remove_as(v, asid);
+
}

static int vhost_vdpa_va_map(struct vhost_vdpa *v,
@@ -1112,8 +1108,6 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev, u32 asid,
if (v->in_batch && ops->set_map)
ops->set_map(vdpa, asid, iotlb);
v->in_batch = false;
- if (!iotlb->nmaps)
- vhost_vdpa_remove_as(v, asid);
break;
default:
r = -EINVAL;
--
2.34.3

2023-04-17 03:35:57

by Jason Wang

Subject: Re: [PATCH v2] vhost_vdpa: fix unmap process in no-batch mode

On Sat, Apr 15, 2023 at 10:20 AM Cindy Lu <[email protected]> wrote:
>
> While using the no-batch mode with vIOMMU enabled
> Qemu will call a large memory to unmap. Much larger than the memory
> mapped to the kernel. The iotlb is NULL in the kernel and will return fail.

This patch looks good but I don't understand the above. I think it's
better to explain why such large unmap will lead to this error:

Is it a batched unmap or a [0, ULONG_MAX] map? How could we end up the NULL?

> Which causes failure.
> To fix this, we will not remove the AS while the iotlb->nmaps is 0.
> This will free in the vhost_vdpa_clean
>
> Signed-off-by: Cindy Lu <[email protected]>

Do we need a fix tag and does it need to go for -stable?

Thanks

> ---
> drivers/vhost/vdpa.c | 8 +-------
> 1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 7be9d9d8f01c..74c7d1f978b7 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -851,11 +851,7 @@ static void vhost_vdpa_unmap(struct vhost_vdpa *v,
> if (!v->in_batch)
> ops->set_map(vdpa, asid, iotlb);
> }
> - /* If we are in the middle of batch processing, delay the free
> - * of AS until BATCH_END.
> - */
> - if (!v->in_batch && !iotlb->nmaps)
> - vhost_vdpa_remove_as(v, asid);
> +
> }
>
> static int vhost_vdpa_va_map(struct vhost_vdpa *v,
> @@ -1112,8 +1108,6 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev, u32 asid,
> if (v->in_batch && ops->set_map)
> ops->set_map(vdpa, asid, iotlb);
> v->in_batch = false;
> - if (!iotlb->nmaps)
> - vhost_vdpa_remove_as(v, asid);
> break;
> default:
> r = -EINVAL;
> --
> 2.34.3
>