[PATCH 14/31] virtio: Add vhost_shadow_vq_get_vring_addr

[Eugenio Pérez]

It reports the shadow virtqueue address from qemu virtual address space.

Since this will be different from the guest's vaddr, but the device can
access it, SVQ takes special care about its alignment & lack of garbage
data. It assumes that IOMMU will work in host_page_size ranges for that.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.h |  4 ++++
 hw/virtio/vhost-shadow-virtqueue.c | 33 ++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h 
b/hw/virtio/vhost-shadow-virtqueue.h
index af8f8264c0..3521e8094d 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -27,6 +27,10 @@ const EventNotifier *vhost_svq_get_dev_kick_notifier(
                                               const VhostShadowVirtqueue *svq);
 const EventNotifier *vhost_svq_get_svq_call_notifier(
                                               const VhostShadowVirtqueue *svq);
+void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
+                              struct vhost_vring_addr *addr);
+size_t vhost_svq_driver_area_size(const VhostShadowVirtqueue *svq);
+size_t vhost_svq_device_area_size(const VhostShadowVirtqueue *svq);
 
 void vhost_svq_stop(VhostShadowVirtqueue *svq);
 
diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
b/hw/virtio/vhost-shadow-virtqueue.c
index a6fb7e3c8f..0f2c2403ff 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -9,12 +9,16 @@
 
 #include "qemu/osdep.h"
 #include "hw/virtio/vhost-shadow-virtqueue.h"
+#include "standard-headers/linux/vhost_types.h"
 
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
 
 /* Shadow virtqueue to relay notifications */
 typedef struct VhostShadowVirtqueue {
+    /* Shadow vring */
+    struct vring vring;
+
     /* Shadow kick notifier, sent to vhost */
     EventNotifier hdev_kick;
     /* Shadow call notifier, sent to vhost */
@@ -195,6 +199,35 @@ void 
vhost_svq_set_guest_call_notifier(VhostShadowVirtqueue *svq, int call_fd)
     event_notifier_init_fd(&svq->svq_call, call_fd);
 }
 
+/*
+ * Get the shadow vq vring address.
+ * @svq Shadow virtqueue
+ * @addr Destination to store address
+ */
+void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
+                              struct vhost_vring_addr *addr)
+{
+    addr->desc_user_addr = (uint64_t)svq->vring.desc;
+    addr->avail_user_addr = (uint64_t)svq->vring.avail;
+    addr->used_user_addr = (uint64_t)svq->vring.used;
+}
+
+size_t vhost_svq_driver_area_size(const VhostShadowVirtqueue *svq)
+{
+    size_t desc_size = sizeof(vring_desc_t) * svq->vring.num;
+    size_t avail_size = offsetof(vring_avail_t, ring) +
+                                             sizeof(uint16_t) * svq->vring.num;
+
+    return ROUND_UP(desc_size + avail_size, qemu_real_host_page_size);
+}
+
+size_t vhost_svq_device_area_size(const VhostShadowVirtqueue *svq)
+{
+    size_t used_size = offsetof(vring_used_t, ring) +
+                                    sizeof(vring_used_elem_t) * svq->vring.num;
+    return ROUND_UP(used_size, qemu_real_host_page_size);
+}
+
 /**
  * Set a new file descriptor for the guest to kick SVQ and notify for avail
  *
-- 
2.27.0