[RFC PATCH v4 20/20] vdpa: Add custom IOTLB translations to SVQ

[Eugenio Pérez]

Use translations added in VhostIOVATree in SVQ.

Now every element needs to store the previous address also, so VirtQueue
can consume the elements properly. This adds a little overhead per VQ
element, having to allocate more memory to stash them. As a possible
optimization, this allocation could be avoided if the descriptor is not
a chain but a single one, but this is left undone.

TODO: iova range should be queried before, and add logic to fail when
GPA is outside of its range and memory listener or svq add it.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.h |   4 +-
 hw/virtio/vhost-shadow-virtqueue.c | 130 ++++++++++++++++++++++++-----
 hw/virtio/vhost-vdpa.c             |  40 ++++++++-
 hw/virtio/trace-events             |   1 +
 4 files changed, 152 insertions(+), 23 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h 
b/hw/virtio/vhost-shadow-virtqueue.h
index b7baa424a7..a0e6b5267a 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -11,6 +11,7 @@
 #define VHOST_SHADOW_VIRTQUEUE_H
 
 #include "hw/virtio/vhost.h"
+#include "hw/virtio/vhost-iova-tree.h"
 
 typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
 
@@ -28,7 +29,8 @@ bool vhost_svq_start(struct vhost_dev *dev, unsigned idx,
 void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,
                     VhostShadowVirtqueue *svq);
 
-VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx);
+VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx,
+                                    VhostIOVATree *iova_map);
 
 void vhost_svq_free(VhostShadowVirtqueue *vq);
 
diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
b/hw/virtio/vhost-shadow-virtqueue.c
index 2fd0bab75d..9db538547e 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -11,12 +11,19 @@
 #include "hw/virtio/vhost-shadow-virtqueue.h"
 #include "hw/virtio/vhost.h"
 #include "hw/virtio/virtio-access.h"
+#include "hw/virtio/vhost-iova-tree.h"
 
 #include "standard-headers/linux/vhost_types.h"
 
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
 
+typedef struct SVQElement {
+    VirtQueueElement elem;
+    void **in_sg_stash;
+    void **out_sg_stash;
+} SVQElement;
+
 /* Shadow virtqueue to relay notifications */
 typedef struct VhostShadowVirtqueue {
     /* Shadow vring */
@@ -46,8 +53,11 @@ typedef struct VhostShadowVirtqueue {
     /* Virtio device */
     VirtIODevice *vdev;
 
+    /* IOVA mapping if used */
+    VhostIOVATree *iova_map;
+
     /* Map for returning guest's descriptors */
-    VirtQueueElement **ring_id_maps;
+    SVQElement **ring_id_maps;
 
     /* Next head to expose to device */
     uint16_t avail_idx_shadow;
@@ -79,13 +89,6 @@ bool vhost_svq_valid_device_features(uint64_t *dev_features)
             continue;
 
         case VIRTIO_F_ACCESS_PLATFORM:
-            /* SVQ needs this feature disabled. Can't continue */
-            if (*dev_features & BIT_ULL(b)) {
-                clear_bit(b, dev_features);
-                r = false;
-            }
-            break;
-
         case VIRTIO_F_VERSION_1:
             /* SVQ needs this feature, so can't continue */
             if (!(*dev_features & BIT_ULL(b))) {
@@ -126,6 +129,64 @@ static void 
vhost_svq_set_notification(VhostShadowVirtqueue *svq, bool enable)
     }
 }
 
+static void vhost_svq_stash_addr(void ***stash, const struct iovec *iov,
+                                 size_t num)
+{
+    size_t i;
+
+    if (num == 0) {
+        return;
+    }
+
+    *stash = g_new(void *, num);
+    for (i = 0; i < num; ++i) {
+        (*stash)[i] = iov[i].iov_base;
+    }
+}
+
+static void vhost_svq_unstash_addr(void **stash, struct iovec *iov, size_t num)
+{
+    size_t i;
+
+    if (num == 0) {
+        return;
+    }
+
+    for (i = 0; i < num; ++i) {
+        iov[i].iov_base = stash[i];
+    }
+    g_free(stash);
+}
+
+static void vhost_svq_translate_addr(const VhostShadowVirtqueue *svq,
+                                     struct iovec *iovec, size_t num)
+{
+    size_t i;
+
+    for (i = 0; i < num; ++i) {
+        VhostDMAMap needle = {
+            .translated_addr = iovec[i].iov_base,
+            .size = iovec[i].iov_len,
+        };
+        size_t off;
+
+        const VhostDMAMap *map = vhost_iova_tree_find_iova(svq->iova_map,
+                                                           &needle);
+        /*
+         * Map cannot be NULL since iova map contains all guest space and
+         * qemu already has a physical address mapped
+         */
+        assert(map);
+
+        /*
+         * Map->iova chunk size is ignored. What to do if descriptor
+         * (addr, size) does not fit is delegated to the device.
+         */
+        off = needle.translated_addr - map->translated_addr;
+        iovec[i].iov_base = (void *)(map->iova + off);
+    }
+}
+
 static void vhost_vring_write_descs(VhostShadowVirtqueue *svq,
                                     const struct iovec *iovec,
                                     size_t num, bool more_descs, bool write)
@@ -156,8 +217,9 @@ static void vhost_vring_write_descs(VhostShadowVirtqueue 
*svq,
 }
 
 static unsigned vhost_svq_add_split(VhostShadowVirtqueue *svq,
-                                    VirtQueueElement *elem)
+                                    SVQElement *svq_elem)
 {
+    VirtQueueElement *elem = &svq_elem->elem;
     int head;
     unsigned avail_idx;
     vring_avail_t *avail = svq->vring.avail;
@@ -167,6 +229,12 @@ static unsigned vhost_svq_add_split(VhostShadowVirtqueue 
*svq,
     /* We need some descriptors here */
     assert(elem->out_num || elem->in_num);
 
+    vhost_svq_stash_addr(&svq_elem->in_sg_stash, elem->in_sg, elem->in_num);
+    vhost_svq_stash_addr(&svq_elem->out_sg_stash, elem->out_sg, elem->out_num);
+
+    vhost_svq_translate_addr(svq, elem->in_sg, elem->in_num);
+    vhost_svq_translate_addr(svq, elem->out_sg, elem->out_num);
+
     vhost_vring_write_descs(svq, elem->out_sg, elem->out_num,
                             elem->in_num > 0, false);
     vhost_vring_write_descs(svq, elem->in_sg, elem->in_num, false, true);
@@ -187,7 +255,7 @@ static unsigned vhost_svq_add_split(VhostShadowVirtqueue 
*svq,
 
 }
 
-static void vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)
+static void vhost_svq_add(VhostShadowVirtqueue *svq, SVQElement *elem)
 {
     unsigned qemu_head = vhost_svq_add_split(svq, elem);
 
@@ -221,7 +289,7 @@ static void vhost_handle_guest_kick(EventNotifier *n)
         }
 
         while (true) {
-            VirtQueueElement *elem = virtqueue_pop(svq->vq, sizeof(*elem));
+            SVQElement *elem = virtqueue_pop(svq->vq, sizeof(*elem));
             if (!elem) {
                 break;
             }
@@ -247,7 +315,7 @@ static bool vhost_svq_more_used(VhostShadowVirtqueue *svq)
     return svq->used_idx != svq->shadow_used_idx;
 }
 
-static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq)
+static SVQElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq)
 {
     vring_desc_t *descs = svq->vring.desc;
     const vring_used_t *used = svq->vring.used;
@@ -279,7 +347,7 @@ static VirtQueueElement 
*vhost_svq_get_buf(VhostShadowVirtqueue *svq)
     descs[used_elem.id].next = svq->free_head;
     svq->free_head = used_elem.id;
 
-    svq->ring_id_maps[used_elem.id]->len = used_elem.len;
+    svq->ring_id_maps[used_elem.id]->elem.len = used_elem.len;
     return g_steal_pointer(&svq->ring_id_maps[used_elem.id]);
 }
 
@@ -296,12 +364,19 @@ static void vhost_svq_handle_call_no_test(EventNotifier 
*n)
 
         vhost_svq_set_notification(svq, false);
         while (true) {
-            g_autofree VirtQueueElement *elem = vhost_svq_get_buf(svq);
-            if (!elem) {
+            g_autofree SVQElement *svq_elem = vhost_svq_get_buf(svq);
+            VirtQueueElement *elem;
+            if (!svq_elem) {
                 break;
             }
 
             assert(i < svq->vring.num);
+            elem = &svq_elem->elem;
+
+            vhost_svq_unstash_addr(svq_elem->in_sg_stash, elem->in_sg,
+                                   elem->in_num);
+            vhost_svq_unstash_addr(svq_elem->out_sg_stash, elem->out_sg,
+                                   elem->out_num);
             virtqueue_fill(vq, elem, elem->len, i++);
         }
 
@@ -451,14 +526,24 @@ void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,
     event_notifier_set_handler(&svq->host_notifier, NULL);
 
     for (i = 0; i < svq->vring.num; ++i) {
-        g_autofree VirtQueueElement *elem = svq->ring_id_maps[i];
+        g_autofree SVQElement *svq_elem = svq->ring_id_maps[i];
+        VirtQueueElement *elem;
+
+        if (!svq_elem) {
+            continue;
+        }
+
+        elem = &svq_elem->elem;
+        vhost_svq_unstash_addr(svq_elem->in_sg_stash, elem->in_sg,
+                               elem->in_num);
+        vhost_svq_unstash_addr(svq_elem->out_sg_stash, elem->out_sg,
+                               elem->out_num);
+
         /*
          * Although the doc says we must unpop in order, it's ok to unpop
          * everything.
          */
-        if (elem) {
-            virtqueue_unpop(svq->vq, elem, elem->len);
-        }
+        virtqueue_unpop(svq->vq, elem, elem->len);
     }
 }
 
@@ -466,7 +551,8 @@ void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,
  * Creates vhost shadow virtqueue, and instruct vhost device to use the shadow
  * methods and file descriptors.
  */
-VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx)
+VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx,
+                                    VhostIOVATree *iova_map)
 {
     int vq_idx = dev->vq_index + idx;
     unsigned num = virtio_queue_get_num(dev->vdev, vq_idx);
@@ -500,11 +586,13 @@ VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev 
*dev, int idx)
     memset(svq->vring.desc, 0, driver_size);
     svq->vring.used = qemu_memalign(qemu_real_host_page_size, device_size);
     memset(svq->vring.used, 0, device_size);
+    svq->iova_map = iova_map;
+
     for (i = 0; i < num - 1; i++) {
         svq->vring.desc[i].next = cpu_to_le16(i + 1);
     }
 
-    svq->ring_id_maps = g_new0(VirtQueueElement *, num);
+    svq->ring_id_maps = g_new0(SVQElement *, num);
     event_notifier_set_handler(&svq->call_notifier,
                                vhost_svq_handle_call);
     return g_steal_pointer(&svq);
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index a9c680b487..f5a12fee9d 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -176,6 +176,18 @@ static void vhost_vdpa_listener_region_add(MemoryListener 
*listener,
                                          vaddr, section->readonly);
 
     llsize = int128_sub(llend, int128_make64(iova));
+    if (v->shadow_vqs_enabled) {
+        VhostDMAMap mem_region = {
+            .translated_addr = vaddr,
+            .size = int128_get64(llsize) - 1,
+            .perm = IOMMU_ACCESS_FLAG(true, section->readonly),
+        };
+
+        int r = vhost_iova_tree_alloc(v->iova_map, &mem_region);
+        assert(r == VHOST_DMA_MAP_OK);
+
+        iova = mem_region.iova;
+    }
 
     ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize),
                              vaddr, section->readonly);
@@ -754,6 +766,23 @@ static bool  vhost_vdpa_force_iommu(struct vhost_dev *dev)
     return true;
 }
 
+static int vhost_vdpa_get_iova_range(struct vhost_dev *dev,
+                                     hwaddr *first, hwaddr *last)
+{
+    int ret;
+    struct vhost_vdpa_iova_range range;
+
+    ret = vhost_vdpa_call(dev, VHOST_VDPA_GET_IOVA_RANGE, &range);
+    if (ret != 0) {
+        return ret;
+    }
+
+    *first = range.first;
+    *last = range.last;
+    trace_vhost_vdpa_get_iova_range(dev, *first, *last);
+    return ret;
+}
+
 /**
  * Maps QEMU vaddr memory to device in a suitable way for shadow virtqueue:
  * - It always reference qemu memory address, not guest's memory.
@@ -881,6 +910,7 @@ static bool vhost_vdpa_svq_start_vq(struct vhost_dev *dev, 
unsigned idx)
 static unsigned vhost_vdpa_enable_svq(struct vhost_vdpa *v, bool enable)
 {
     struct vhost_dev *hdev = v->dev;
+    hwaddr iova_first, iova_last;
     unsigned n;
     int r;
 
@@ -894,7 +924,7 @@ static unsigned vhost_vdpa_enable_svq(struct vhost_vdpa *v, 
bool enable)
         /* Allocate resources */
         assert(v->shadow_vqs->len == 0);
         for (n = 0; n < hdev->nvqs; ++n) {
-            VhostShadowVirtqueue *svq = vhost_svq_new(hdev, n);
+            VhostShadowVirtqueue *svq = vhost_svq_new(hdev, n, v->iova_map);
             if (unlikely(!svq)) {
                 g_ptr_array_set_size(v->shadow_vqs, 0);
                 return 0;
@@ -903,6 +933,8 @@ static unsigned vhost_vdpa_enable_svq(struct vhost_vdpa *v, 
bool enable)
         }
     }
 
+    r = vhost_vdpa_get_iova_range(hdev, &iova_first, &iova_last);
+    assert(r == 0);
     r = vhost_vdpa_vring_pause(hdev);
     assert(r == 0);
 
@@ -913,6 +945,12 @@ static unsigned vhost_vdpa_enable_svq(struct vhost_vdpa 
*v, bool enable)
         }
     }
 
+    memory_listener_unregister(&v->listener);
+    if (vhost_vdpa_dma_unmap(v, iova_first,
+                             (iova_last - iova_first) & TARGET_PAGE_MASK)) {
+        error_report("Fail to invalidate device iotlb");
+    }
+
     /* Reset device so it can be configured */
     r = vhost_vdpa_dev_start(hdev, false);
     assert(r == 0);
diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index 8ed19e9d0c..650e521e35 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -52,6 +52,7 @@ vhost_vdpa_set_vring_call(void *dev, unsigned int index, int 
fd) "dev: %p index:
 vhost_vdpa_get_features(void *dev, uint64_t features) "dev: %p features: 
0x%"PRIx64
 vhost_vdpa_set_owner(void *dev) "dev: %p"
 vhost_vdpa_vq_get_addr(void *dev, void *vq, uint64_t desc_user_addr, uint64_t 
avail_user_addr, uint64_t used_user_addr) "dev: %p vq: %p desc_user_addr: 
0x%"PRIx64" avail_user_addr: 0x%"PRIx64" used_user_addr: 0x%"PRIx64
+vhost_vdpa_get_iova_range(void *dev, uint64_t first, uint64_t last) "dev: %p 
first: 0x%"PRIx64" last: 0x%"PRIx64
 
 # virtio.c
 virtqueue_alloc_element(void *elem, size_t sz, unsigned in_num, unsigned 
out_num) "elem %p size %zd in_num %u out_num %u"
-- 
2.27.0