[dpdk-dev] [RFC 11/19] vhost: introduce guest IOVA to backend VA helper

[Maxime Coquelin <maxime.coquelin@redhat.com>]

This patch introduces vhost_iova_to_vva() function to translate
guest's IO virtual adresses to backend's virtual addresses.

When IOMMU is enabled, the IOTLB cache is queried to get the
translation. If missing from the IOTLB cache, an IOTLB_MISS request
is sent to Qemu, and IOTLB cache is queried again on IOTLB event
notification.

When IOMMU is disabled, the passed address is a guest's physical
address, so the legacy rte_vhost_gpa_to_vva() API is used.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost.c | 35 +++++++++++++++++++++++++++++++++++
 lib/librte_vhost/vhost.h |  3 +++
 2 files changed, 38 insertions(+)

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 3897f9c..7920216 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -47,9 +47,11 @@
 #include <rte_malloc.h>
 #include <rte_rwlock.h>
 #include <rte_vhost.h>
+#include <rte_rwlock.h>
 
 #include "iotlb.h"
 #include "vhost.h"
+#include "vhost_user.h"
 
 struct vhost_device {
 	struct virtio_net *dev;
@@ -59,6 +61,39 @@ struct vhost_device {
 /* Declared as static so that .lock is initialized */
 static struct vhost_device vhost_devices[MAX_VHOST_DEVICE];
 
+uint64_t vhost_iova_to_vva(struct virtio_net *dev, struct vhost_virtqueue *vq,
+			uint64_t iova, uint64_t size, uint8_t perm)
+{
+	uint64_t vva, tmp_size;
+	int ret;
+
+	if (unlikely(!size))
+		return 0;
+
+	if (!(dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)))
+		return rte_vhost_gpa_to_vva(dev->mem, iova);
+
+	do {
+		tmp_size = size;
+
+		vva = vhost_user_iotlb_find(vq, iova, &tmp_size, perm);
+		if (tmp_size == size)
+			return vva;
+
+		/* Not in IOTLB cache */
+		ret = vhost_user_iotlb_miss(dev, iova + tmp_size, perm);
+		if (ret)
+			return 0;
+
+		while (!rte_atomic16_cmpset((volatile uint16_t *)
+					&vq->iotlb_event.cnt, 1, 0))
+			rte_pause();
+
+	} while (likely(dev->flags & VIRTIO_DEV_RUNNING));
+
+	return 0;
+}
+
 static inline struct virtio_net *
 __get_device(int vid)
 {
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 3242658..5c39d88 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -353,4 +353,7 @@ struct vhost_device_ops const *vhost_driver_callback_get(const char *path);
 void vhost_backend_cleanup(struct virtio_net *dev);
 void notify_iotlb_event(struct virtio_net *dev);
 
+uint64_t vhost_iova_to_vva(struct virtio_net *dev, struct vhost_virtqueue *vq,
+			uint64_t iova, uint64_t size, uint8_t perm);
+
 #endif /* _VHOST_NET_CDEV_H_ */
-- 
2.9.4