[Qemu-devel] [PATCH 1/2] vhost: avoid to start/stop virtqueue which is not ready

[Qemu-devel] [PATCH 1/2] vhost: avoid to start/stop virtqueue which is not ready

[Jia He]

In our Armv8a server, we try to configure the vhost scsi but fail
to boot up the guest (-machine virt-2.10). The guest's boot failure
is very early, even earlier than grub.

There are 3 virtqueues (ctrl, event and cmd) for virtio scsi device,
but ovmf and seabios will only set the physical address for the 3rd
one (cmd). Then in vhost_virtqueue_start(), virtio_queue_get_desc_addr
will be 0 for ctrl and event vq when qemu negotiates with ovmf. So
vhost_memory_map fails with ENOMEM.

This patch just fixs it by early quitting the virtqueue start/stop
when virtio_queue_get_desc_addr is 0.

Btw, after guest kernel starts, all the 3 queues will be initialized
and set address correctly.

Already tested on Arm64 and X86_64 qemu.

Signed-off-by: Jia He <jia.he@hxt-semitech.com>
---
 hw/virtio/vhost.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 4a44e6e..00f2512 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -345,6 +345,10 @@ static int vhost_verify_ring_mappings(struct vhost_dev *dev,
     for (i = 0; i < dev->nvqs; ++i) {
         struct vhost_virtqueue *vq = dev->vqs + i;
 
+        if (vq->desc_phys == 0) {
+            continue;
+        }
+
         j = 0;
         r = vhost_verify_ring_part_mapping(
                 vq->desc, vq->desc_phys, vq->desc_size,
@@ -881,6 +885,11 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
     };
     struct VirtQueue *vvq = virtio_get_queue(vdev, idx);
 
+    a = virtio_queue_get_desc_addr(vdev, idx);
+    if (a == 0) {
+        /* Queue might not be ready for start */
+        return 0;
+    }
 
     vq->num = state.num = virtio_queue_get_num(vdev, idx);
     r = dev->vhost_ops->vhost_set_vring_num(dev, &state);
@@ -906,7 +915,7 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
     }
 
     vq->desc_size = s = l = virtio_queue_get_desc_size(vdev, idx);
-    vq->desc_phys = a = virtio_queue_get_desc_addr(vdev, idx);
+    vq->desc_phys = a;
     vq->desc = vhost_memory_map(dev, a, &l, 0);
     if (!vq->desc || l != s) {
         r = -ENOMEM;
@@ -989,6 +998,13 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev,
         .index = vhost_vq_index,
     };
     int r;
+    int a;
+
+    a = virtio_queue_get_desc_addr(vdev, idx);
+    if (a == 0) {
+        /* Don't stop the virtqueue which might have not been started */
+        return;
+    }
 
     r = dev->vhost_ops->vhost_get_vring_base(dev, &state);
     if (r < 0) {
-- 
2.7.4

[Qemu-devel] [PATCH 2/2] vhost: fix incorrect check in vhost_verify_ring_mappings

[Jia He]

In commit 0ca1fd2d6878 ("vhost: Simplify ring verification checks"),
it checks the virtqueue desc mapping for 3 times.

Fixed: commit 0ca1fd2d6878 ("vhost: Simplify ring verification checks")
Signed-off-by: Jia He <jia.he@hxt-semitech.com>
---
 hw/virtio/vhost.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 00f2512..bbf6c0c 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -359,7 +359,7 @@ static int vhost_verify_ring_mappings(struct vhost_dev *dev,
 
         j++;
         r = vhost_verify_ring_part_mapping(
-                vq->desc, vq->desc_phys, vq->desc_size,
+                vq->avail, vq->avail_phys, vq->avail_size,
                 reg_hva, reg_gpa, reg_size);
         if (r) {
             break;
@@ -367,7 +367,7 @@ static int vhost_verify_ring_mappings(struct vhost_dev *dev,
 
         j++;
         r = vhost_verify_ring_part_mapping(
-                vq->desc, vq->desc_phys, vq->desc_size,
+                vq->used, vq->used_phys, vq->used_size,
                 reg_hva, reg_gpa, reg_size);
         if (r) {
             break;
-- 
2.7.4

Re: [Qemu-devel] [PATCH 2/2] vhost: fix incorrect check in vhost_verify_ring_mappings

[Dr. David Alan Gilbert]

* Jia He (hejianet@gmail.com) wrote:
> In commit 0ca1fd2d6878 ("vhost: Simplify ring verification checks"),
> it checks the virtqueue desc mapping for 3 times.
> 
> Fixed: commit 0ca1fd2d6878 ("vhost: Simplify ring verification checks")
> Signed-off-by: Jia He <jia.he@hxt-semitech.com>

Oops, well spotted; copy & paste strikes again.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  hw/virtio/vhost.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 00f2512..bbf6c0c 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -359,7 +359,7 @@ static int vhost_verify_ring_mappings(struct vhost_dev *dev,
>  
>          j++;
>          r = vhost_verify_ring_part_mapping(
> -                vq->desc, vq->desc_phys, vq->desc_size,
> +                vq->avail, vq->avail_phys, vq->avail_size,
>                  reg_hva, reg_gpa, reg_size);
>          if (r) {
>              break;
> @@ -367,7 +367,7 @@ static int vhost_verify_ring_mappings(struct vhost_dev *dev,
>  
>          j++;
>          r = vhost_verify_ring_part_mapping(
> -                vq->desc, vq->desc_phys, vq->desc_size,
> +                vq->used, vq->used_phys, vq->used_size,
>                  reg_hva, reg_gpa, reg_size);
>          if (r) {
>              break;
> -- 
> 2.7.4
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK