From ad19f7aad9e2ff9a007eddbd9a19b61a9c1af769 Mon Sep 17 00:00:00 2001
From: Jim Somerville <Jim.Somerville@windriver.com
Date: Fri, 26 Apr 2019 17:41:04 -0300
Subject: [PATCH] STX: Suspend/Resume for VMs with PCIPT+Virtio

When we have a Passthrough or a SR-IOV device, the plug/unplug of these
devices causes the guest memory map to change.

When the vhost code in qemu detects that the guest memory map changed,
it verifies that the virtio vring mappings into its own address space
did not change and sends the vhost backend the VHOST_SET_MEM_TABLE
message so that the backend can update its mapping based on the new
guest memory map.

If this guest memory map change happens after the virtio device has
been initialized and started, we get into the situation where ports
are brought down as part of the VHOST_SET_MEM_TABLE message handling
and has nothing to restart the device.

The root cause of this issue was that the mappings for the vring was
changing when we get a new VHOST_USER_SET_MEM_TABLE message and we
were trying to restart the device with the old vring mapping.

The correct fix is to send a VHOST_SET_VRING_ADDR message from qemu
which will force the mapping to be recalculated based on the new
memory map.

Signed-off-by: Jim Somerville <Jim.Somerville@windriver.com>
[ Trimmed the shortlog ]
Signed-off-by: Rafael Falcao <Rafael.VieiraFalcao@windriver.com>
---
 hw/virtio/vhost.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 614ccc2bcb..05c045925a 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -61,6 +61,10 @@ bool vhost_has_free_slot(void)
     return slots_limit > used_memslots;
 }
 
+static int vhost_virtqueue_set_addr(struct vhost_dev *dev,
+                                    struct vhost_virtqueue *vq,
+                                    unsigned idx, bool enable_log);
+
 static void vhost_dev_sync_region(struct vhost_dev *dev,
                                   MemoryRegionSection *section,
                                   uint64_t mfirst, uint64_t mlast,
@@ -448,6 +452,21 @@ static void vhost_begin(MemoryListener *listener)
     dev->n_tmp_sections = 0;
 }
 
+static void vhost_update_backend_ring_mappings(struct vhost_dev *dev)
+{
+    int i,r;
+
+    if(dev->vhost_ops->backend_type != VHOST_BACKEND_TYPE_USER) {
+        return;
+    }
+
+    for (i = 0; i < dev->nvqs; ++i) {
+        r = vhost_virtqueue_set_addr(dev, dev->vqs + i, i, dev->log_enabled);
+        assert(r >= 0);
+    }
+    return;
+}
+
 static void vhost_commit(MemoryListener *listener)
 {
     struct vhost_dev *dev = container_of(listener, struct vhost_dev,
@@ -524,7 +543,7 @@ static void vhost_commit(MemoryListener *listener)
         if (r < 0) {
             VHOST_OPS_DEBUG("vhost_set_mem_table failed");
         }
-        goto out;
+        goto vring_mapping;
     }
     log_size = vhost_get_log_size(dev);
     /* We allocate an extra 4K bytes to log,
@@ -543,6 +562,11 @@ static void vhost_commit(MemoryListener *listener)
         vhost_dev_log_resize(dev, log_size);
     }
 
+vring_mapping:
+    /* For vhost-user backend, update the vring mappings after we sent a new
+     * guest memory map. */
+    vhost_update_backend_ring_mappings(dev);
+
 out:
     /* Deref the old list of sections, this must happen _after_ the
      * vhost_set_mem_table to ensure the client isn't still using the
-- 
2.25.1