From 893dffb820973361bcef33612a6b924554a856c1 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= <eperezma@redhat.com>

Date: Thu, 21 Jul 2022 15:38:55 +0200

Subject: [PATCH 13/32] vhost: Check for queue full at vhost_svq_add

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RH-Author: Eugenio Pérez <eperezma@redhat.com>

RH-MergeRequest: 108: Net Control Virtqueue shadow Support

RH-Commit: [13/27] d4bd8299fb7733a1e190618dfc92b4b53b7bbeb3 (eperezmartin/qemu-kvm)

RH-Bugzilla: 1939363

RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>

RH-Acked-by: Cindy Lu <lulu@redhat.com>

RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

Bugzilla: https://bugzilla.redhat.com/1939363

Upstream Status: git://git.qemu.org/qemu.git

commit f20b70eb5a68cfd8fef74a13ccdd494ef1cb0221

Author: Eugenio Pérez <eperezma@redhat.com>

Date:   Wed Jul 20 08:59:32 2022 +0200

    vhost: Check for queue full at vhost_svq_add

    The series need to expose vhost_svq_add with full functionality,

    including checking for full queue.

    Signed-off-by: Eugenio Pérez <eperezma@redhat.com>

    Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

    Signed-off-by: Jason Wang <jasowang@redhat.com>

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>

---

 hw/virtio/vhost-shadow-virtqueue.c | 59 +++++++++++++++++-------------

 1 file changed, 33 insertions(+), 26 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c

index e3fc3c2658..1d2bab287b 100644

--- a/hw/virtio/vhost-shadow-virtqueue.c

+++ b/hw/virtio/vhost-shadow-virtqueue.c

@@ -233,21 +233,29 @@ static void vhost_svq_kick(VhostShadowVirtqueue *svq)

  * Add an element to a SVQ.

  *

  * The caller must check that there is enough slots for the new element. It

- * takes ownership of the element: In case of failure, it is free and the SVQ

- * is considered broken.

+ * takes ownership of the element: In case of failure not ENOSPC, it is free.

+ *

+ * Return -EINVAL if element is invalid, -ENOSPC if dev queue is full

  */

-static bool vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)

+static int vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)

 {

     unsigned qemu_head;

-    bool ok = vhost_svq_add_split(svq, elem, &qemu_head);

+    unsigned ndescs = elem->in_num + elem->out_num;

+    bool ok;

+

+    if (unlikely(ndescs > vhost_svq_available_slots(svq))) {

+        return -ENOSPC;

+    }

+

+    ok = vhost_svq_add_split(svq, elem, &qemu_head);

     if (unlikely(!ok)) {

         g_free(elem);

-        return false;

+        return -EINVAL;

     }

     svq->ring_id_maps[qemu_head] = elem;

     vhost_svq_kick(svq);

-    return true;

+    return 0;

 }

 /**

@@ -274,7 +282,7 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)

         while (true) {

             VirtQueueElement *elem;

-            bool ok;

+            int r;

             if (svq->next_guest_avail_elem) {

                 elem = g_steal_pointer(&svq->next_guest_avail_elem);

@@ -286,25 +294,24 @@ static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)

                 break;

             }

-            if (elem->out_num + elem->in_num > vhost_svq_available_slots(svq)) {

-                /*

-                 * This condition is possible since a contiguous buffer in GPA

-                 * does not imply a contiguous buffer in qemu's VA

-                 * scatter-gather segments. If that happens, the buffer exposed

-                 * to the device needs to be a chain of descriptors at this

-                 * moment.

-                 *

-                 * SVQ cannot hold more available buffers if we are here:

-                 * queue the current guest descriptor and ignore further kicks

-                 * until some elements are used.

-                 */

-                svq->next_guest_avail_elem = elem;

-                return;

-            }

-

-            ok = vhost_svq_add(svq, elem);

-            if (unlikely(!ok)) {

-                /* VQ is broken, just return and ignore any other kicks */

+            r = vhost_svq_add(svq, elem);

+            if (unlikely(r != 0)) {

+                if (r == -ENOSPC) {

+                    /*

+                     * This condition is possible since a contiguous buffer in

+                     * GPA does not imply a contiguous buffer in qemu's VA

+                     * scatter-gather segments. If that happens, the buffer

+                     * exposed to the device needs to be a chain of descriptors

+                     * at this moment.

+                     *

+                     * SVQ cannot hold more available buffers if we are here:

+                     * queue the current guest descriptor and ignore kicks

+                     * until some elements are used.

+                     */

+                    svq->next_guest_avail_elem = elem;

+                }

+

+                /* VQ is full or broken, just return and ignore kicks */

                 return;

             }

         }

-- 

2.31.1