Re: [PATCH vfio 01/11] virtio-pci: Use virtio pci device layer vq info instead of generic one

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On 2023-09-21 a.m.9:46, Michael S. Tsirkin wrote:
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On Thu, Sep 21, 2023 at 03:40:30PM +0300, Yishai Hadas wrote:
From: Feng Liu <feliu@xxxxxxxxxx>

Currently VQ deletion callback vp_del_vqs() processes generic
virtio_device level VQ list instead of VQ information available at PCI

To adhere to the layering, use the pci device level VQ information
stored in the virtqueues or vqs.

This also prepares the code to handle PCI layer admin vq life cycle to
be managed within the pci layer and thereby avoid undesired deletion of
admin vq by upper layer drivers (net, console, vfio), in the del_vqs()

Signed-off-by: Feng Liu <feliu@xxxxxxxxxx>
Reviewed-by: Parav Pandit <parav@xxxxxxxxxx>
Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
Signed-off-by: Yishai Hadas <yishaih@xxxxxxxxxx>
  drivers/virtio/virtio_pci_common.c | 12 +++++++++---
  drivers/virtio/virtio_pci_common.h |  1 +
  2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index c2524a7207cf..7a3e6edc4dd6 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -232,12 +232,16 @@ static void vp_del_vq(struct virtqueue *vq)
  void vp_del_vqs(struct virtio_device *vdev)
       struct virtio_pci_device *vp_dev = to_vp_device(vdev);
-     struct virtqueue *vq, *n;
+     struct virtqueue *vq;
       int i;

-     list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
+     for (i = 0; i < vp_dev->nvqs; i++) {
+             if (!vp_dev->vqs[i])
+                     continue;
+             vq = vp_dev->vqs[i]->vq;
               if (vp_dev->per_vq_vectors) {
-                     int v = vp_dev->vqs[vq->index]->msix_vector;
+                     int v = vp_dev->vqs[i]->msix_vector;

                       if (v != VIRTIO_MSI_NO_VECTOR) {
                               int irq = pci_irq_vector(vp_dev->pci_dev, v);
@@ -294,6 +298,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned int nvqs,
       vp_dev->vqs = kcalloc(nvqs, sizeof(*vp_dev->vqs), GFP_KERNEL);
       if (!vp_dev->vqs)
               return -ENOMEM;
+     vp_dev->nvqs = nvqs;

       if (per_vq_vectors) {
               /* Best option: one for change interrupt, one per vq. */
@@ -365,6 +370,7 @@ static int vp_find_vqs_intx(struct virtio_device *vdev, unsigned int nvqs,
       vp_dev->vqs = kcalloc(nvqs, sizeof(*vp_dev->vqs), GFP_KERNEL);
       if (!vp_dev->vqs)
               return -ENOMEM;
+     vp_dev->nvqs = nvqs;

       err = request_irq(vp_dev->pci_dev->irq, vp_interrupt, IRQF_SHARED,
                       dev_name(&vdev->dev), vp_dev);
diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
index 4b773bd7c58c..602021967aaa 100644
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h
@@ -60,6 +60,7 @@ struct virtio_pci_device {

       /* array of all queues for house-keeping */
       struct virtio_pci_vq_info **vqs;
+     u32 nvqs;

I don't much like it that we are adding more duplicated info here.
In fact, we tried removing the vqs array in
5c34d002dcc7a6dd665a19d098b4f4cd5501ba1a - there was some bug in that
patch and the author didn't have the time to debug
so I reverted but I don't really think we need to add to that.

Hi Michael

As explained in commit message, this patch is mainly to prepare for the subsequent admin vq patches.

The admin vq is also established using the common mechanism of vring, and is added to vdev->vqs in __vring_new_virtqueue(). So vdev->vqs contains all virtqueues, including rxq, txq, ctrlvq and admin vq.

admin vq should be managed by the virito_pci layer and should not be created or deleted by upper driver (net, blk); When the upper driver was unloaded, it will call del_vqs() interface, which wll call vp_del_vqs(), and vp_del_vqs() should not delete the admin vq, but only delete the virtqueues created by the upper driver such as rxq, txq, and ctrlq.

vp_dev->vqs[] array only contains virtqueues created by upper driver such as rxq, txq, ctrlq. Traversing vp_dev->vqs array can only delete the upper virtqueues, without the admin vq. Use the vdev->vqs linked list cannot meet the needs.

Can such an explanation be explained clearly? Or do you have any other alternative methods?

       /* MSI-X support */
       int msix_enabled;

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