[Qemu-devel] [RFC PATCH 1/8] virtio: convert to use DMA api

[Jason Wang]

Currently, all virtio devices bypass IOMMU completely. This is because
address_space_memory is assumed and used during DMA emulation. This
patch converts the virtio core API to use DMA API. This idea is

- introducing a new transport specific helper to query the dma address
  space. (only pci version is implemented).
- query and use this address space during virtio device guest memory
  accessing

With this virtio devices will not bypass IOMMU anymore. Tested with
intel_iommu=on/strict with:

- virtio guest DMA series posted in https://lkml.org/lkml/2015/10/28/64.
- vfio (unsafe interrupt mode) dpdk l2fwd in guest

TODO:
- Feature bit for this
- Implement this for all transports

Cc: Michael S. Tsirkin <address@hidden>
Cc: Stefan Hajnoczi <address@hidden>
Cc: Kevin Wolf <address@hidden>
Cc: Amit Shah <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Cc: address@hidden
Signed-off-by: Jason Wang <address@hidden>
---
 hw/block/virtio-blk.c             |  2 +-
 hw/char/virtio-serial-bus.c       |  3 +-
 hw/scsi/virtio-scsi.c             |  4 ++-
 hw/virtio/virtio-pci.c            |  9 ++++++
 hw/virtio/virtio.c                | 58 +++++++++++++++++++++++----------------
 include/hw/virtio/virtio-access.h | 42 +++++++++++++++++++++-------
 include/hw/virtio/virtio-bus.h    |  1 +
 include/hw/virtio/virtio.h        |  4 +--
 8 files changed, 85 insertions(+), 38 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index cb710f1..9411f99 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -829,7 +829,7 @@ static int virtio_blk_load_device(VirtIODevice *vdev, 
QEMUFile *f,
 
     while (qemu_get_sbyte(f)) {
         VirtIOBlockReq *req;
-        req = qemu_get_virtqueue_element(f, sizeof(VirtIOBlockReq));
+        req = qemu_get_virtqueue_element(vdev, f, sizeof(VirtIOBlockReq));
         virtio_blk_init_request(s, req);
         req->next = s->rq;
         s->rq = req;
diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index 99cb683..bdc5393 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -687,6 +687,7 @@ static void virtio_serial_post_load_timer_cb(void *opaque)
 static int fetch_active_ports_list(QEMUFile *f, int version_id,
                                    VirtIOSerial *s, uint32_t nr_active_ports)
 {
+    VirtIODevice *vdev = VIRTIO_DEVICE(s);
     uint32_t i;
 
     s->post_load = g_malloc0(sizeof(*s->post_load));
@@ -722,7 +723,7 @@ static int fetch_active_ports_list(QEMUFile *f, int 
version_id,
                 qemu_get_be64s(f, &port->iov_offset);
 
                 port->elem =
-                    qemu_get_virtqueue_element(f, sizeof(VirtQueueElement));
+                    qemu_get_virtqueue_element(vdev, f, 
sizeof(VirtQueueElement));
 
                 /*
                  *  Port was throttled on source machine.  Let's
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 0c30d2e..26ce701 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -196,12 +196,14 @@ static void *virtio_scsi_load_request(QEMUFile *f, 
SCSIRequest *sreq)
     SCSIBus *bus = sreq->bus;
     VirtIOSCSI *s = container_of(bus, VirtIOSCSI, bus);
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
+    VirtIODevice *vdev = VIRTIO_DEVICE(s);
     VirtIOSCSIReq *req;
     uint32_t n;
 
     qemu_get_be32s(f, &n);
     assert(n < vs->conf.num_queues);
-    req = qemu_get_virtqueue_element(f, sizeof(VirtIOSCSIReq) + vs->cdb_size);
+    req = qemu_get_virtqueue_element(vdev, f,
+                                     sizeof(VirtIOSCSIReq) + vs->cdb_size);
     virtio_scsi_init_req(s, vs->cmd_vqs[n], req);
 
     if (virtio_scsi_parse_req(req, sizeof(VirtIOSCSICmdReq) + vs->cdb_size,
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 0dadb66..5508b1c 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1211,6 +1211,14 @@ static int virtio_pci_query_nvectors(DeviceState *d)
     return proxy->nvectors;
 }
 
+static AddressSpace *virtio_pci_get_dma_as(DeviceState *d)
+{
+    VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
+    PCIDevice *dev = &proxy->pci_dev;
+
+    return pci_get_address_space(dev);
+}
+
 static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
                                    struct virtio_pci_cap *cap)
 {
@@ -2495,6 +2503,7 @@ static void virtio_pci_bus_class_init(ObjectClass *klass, 
void *data)
     k->device_plugged = virtio_pci_device_plugged;
     k->device_unplugged = virtio_pci_device_unplugged;
     k->query_nvectors = virtio_pci_query_nvectors;
+    k->get_dma_as = virtio_pci_get_dma_as;
 }
 
 static const TypeInfo virtio_pci_bus_info = {
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 08275a9..37c9951 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -21,6 +21,7 @@
 #include "hw/virtio/virtio-bus.h"
 #include "migration/migration.h"
 #include "hw/virtio/virtio-access.h"
+#include "sysemu/dma.h"
 
 /*
  * The alignment to use between consumer and producer parts of vring.
@@ -118,7 +119,7 @@ void virtio_queue_update_rings(VirtIODevice *vdev, int n)
 static void vring_desc_read(VirtIODevice *vdev, VRingDesc *desc,
                             hwaddr desc_pa, int i)
 {
-    address_space_read(&address_space_memory, desc_pa + i * sizeof(VRingDesc),
+    address_space_read(virtio_get_dma_as(vdev), desc_pa + i * 
sizeof(VRingDesc),
                        MEMTXATTRS_UNSPECIFIED, (void *)desc, 
sizeof(VRingDesc));
     virtio_tswap64s(vdev, &desc->addr);
     virtio_tswap32s(vdev, &desc->len);
@@ -160,7 +161,7 @@ static inline void vring_used_write(VirtQueue *vq, 
VRingUsedElem *uelem,
     virtio_tswap32s(vq->vdev, &uelem->id);
     virtio_tswap32s(vq->vdev, &uelem->len);
     pa = vq->vring.used + offsetof(VRingUsed, ring[i]);
-    address_space_write(&address_space_memory, pa, MEMTXATTRS_UNSPECIFIED,
+    address_space_write(virtio_get_dma_as(vq->vdev), pa, 
MEMTXATTRS_UNSPECIFIED,
                        (void *)uelem, sizeof(VRingUsedElem));
 }
 
@@ -240,6 +241,7 @@ int virtio_queue_empty(VirtQueue *vq)
 static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
                                unsigned int len)
 {
+    AddressSpace *dma_as = virtio_get_dma_as(vq->vdev);
     unsigned int offset;
     int i;
 
@@ -247,17 +249,17 @@ static void virtqueue_unmap_sg(VirtQueue *vq, const 
VirtQueueElement *elem,
     for (i = 0; i < elem->in_num; i++) {
         size_t size = MIN(len - offset, elem->in_sg[i].iov_len);
 
-        cpu_physical_memory_unmap(elem->in_sg[i].iov_base,
-                                  elem->in_sg[i].iov_len,
-                                  1, size);
+        dma_memory_unmap(dma_as, elem->in_sg[i].iov_base, 
elem->in_sg[i].iov_len,
+                         DMA_DIRECTION_FROM_DEVICE, size);
 
         offset += size;
     }
 
     for (i = 0; i < elem->out_num; i++)
-        cpu_physical_memory_unmap(elem->out_sg[i].iov_base,
-                                  elem->out_sg[i].iov_len,
-                                  0, elem->out_sg[i].iov_len);
+        dma_memory_unmap(dma_as, elem->out_sg[i].iov_base,
+                         elem->out_sg[i].iov_len,
+                         DMA_DIRECTION_TO_DEVICE,
+                         elem->out_sg[i].iov_len);
 }
 
 void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
@@ -447,7 +449,8 @@ int virtqueue_avail_bytes(VirtQueue *vq, unsigned int 
in_bytes,
     return in_bytes <= in_total && out_bytes <= out_total;
 }
 
-static void virtqueue_map_desc(unsigned int *p_num_sg, hwaddr *addr, struct 
iovec *iov,
+static void virtqueue_map_desc(VirtIODevice *vdev,
+                               unsigned int *p_num_sg, hwaddr *addr, struct 
iovec *iov,
                                unsigned int max_num_sg, bool is_write,
                                hwaddr pa, size_t sz)
 {
@@ -462,7 +465,10 @@ static void virtqueue_map_desc(unsigned int *p_num_sg, 
hwaddr *addr, struct iove
             exit(1);
         }
 
-        iov[num_sg].iov_base = cpu_physical_memory_map(pa, &len, is_write);
+        iov[num_sg].iov_base = dma_memory_map(virtio_get_dma_as(vdev), pa, 
&len,
+                                              is_write ?
+                                              DMA_DIRECTION_FROM_DEVICE:
+                                              DMA_DIRECTION_TO_DEVICE);
         iov[num_sg].iov_len = len;
         addr[num_sg] = pa;
 
@@ -473,9 +479,9 @@ static void virtqueue_map_desc(unsigned int *p_num_sg, 
hwaddr *addr, struct iove
     *p_num_sg = num_sg;
 }
 
-static void virtqueue_map_iovec(struct iovec *sg, hwaddr *addr,
-                                unsigned int *num_sg, unsigned int max_size,
-                                int is_write)
+static void virtqueue_map_iovec(VirtIODevice *vdev, struct iovec *sg,
+                                hwaddr *addr, unsigned int *num_sg,
+                                unsigned int max_size, int is_write)
 {
     unsigned int i;
     hwaddr len;
@@ -494,7 +500,10 @@ static void virtqueue_map_iovec(struct iovec *sg, hwaddr 
*addr,
 
     for (i = 0; i < *num_sg; i++) {
         len = sg[i].iov_len;
-        sg[i].iov_base = cpu_physical_memory_map(addr[i], &len, is_write);
+        sg[i].iov_base = dma_memory_map(virtio_get_dma_as(vdev),
+                                        addr[i], &len, is_write ?
+                                        DMA_DIRECTION_FROM_DEVICE :
+                                        DMA_DIRECTION_TO_DEVICE);
         if (!sg[i].iov_base) {
             error_report("virtio: error trying to map MMIO memory");
             exit(1);
@@ -506,12 +515,15 @@ static void virtqueue_map_iovec(struct iovec *sg, hwaddr 
*addr,
     }
 }
 
-void virtqueue_map(VirtQueueElement *elem)
+void virtqueue_map(VirtIODevice *vdev, VirtQueueElement *elem)
 {
-    virtqueue_map_iovec(elem->in_sg, elem->in_addr, &elem->in_num,
-                        VIRTQUEUE_MAX_SIZE, 1);
-    virtqueue_map_iovec(elem->out_sg, elem->out_addr, &elem->out_num,
-                        VIRTQUEUE_MAX_SIZE, 0);
+    virtqueue_map_iovec(vdev, elem->in_sg, elem->in_addr, &elem->in_num,
+                        MIN(ARRAY_SIZE(elem->in_sg), 
ARRAY_SIZE(elem->in_addr)),
+                        1);
+    virtqueue_map_iovec(vdev, elem->out_sg, elem->out_addr, &elem->out_num,
+                        MIN(ARRAY_SIZE(elem->out_sg),
+                        ARRAY_SIZE(elem->out_addr)),
+                        0);
 }
 
 void *virtqueue_alloc_element(size_t sz, unsigned out_num, unsigned in_num)
@@ -580,14 +592,14 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
     /* Collect all the descriptors */
     do {
         if (desc.flags & VRING_DESC_F_WRITE) {
-            virtqueue_map_desc(&in_num, addr + out_num, iov + out_num,
+            virtqueue_map_desc(vdev, &in_num, addr + out_num, iov + out_num,
                                VIRTQUEUE_MAX_SIZE - out_num, true, desc.addr, 
desc.len);
         } else {
             if (in_num) {
                 error_report("Incorrect order for descriptors");
                 exit(1);
             }
-            virtqueue_map_desc(&out_num, addr, iov,
+            virtqueue_map_desc(vdev, &out_num, addr, iov,
                                VIRTQUEUE_MAX_SIZE, false, desc.addr, desc.len);
         }
 
@@ -633,7 +645,7 @@ typedef struct VirtQueueElementOld {
     struct iovec out_sg[VIRTQUEUE_MAX_SIZE];
 } VirtQueueElementOld;
 
-void *qemu_get_virtqueue_element(QEMUFile *f, size_t sz)
+void *qemu_get_virtqueue_element(VirtIODevice *vdev, QEMUFile *f, size_t sz)
 {
     VirtQueueElement *elem;
     VirtQueueElementOld data;
@@ -664,7 +676,7 @@ void *qemu_get_virtqueue_element(QEMUFile *f, size_t sz)
         elem->out_sg[i].iov_len = data.out_sg[i].iov_len;
     }
 
-    virtqueue_map(elem);
+    virtqueue_map(vdev, elem);
     return elem;
 }
 
diff --git a/include/hw/virtio/virtio-access.h 
b/include/hw/virtio/virtio-access.h
index 8dc84f5..967cc75 100644
--- a/include/hw/virtio/virtio-access.h
+++ b/include/hw/virtio/virtio-access.h
@@ -15,8 +15,20 @@
 #ifndef _QEMU_VIRTIO_ACCESS_H
 #define _QEMU_VIRTIO_ACCESS_H
 #include "hw/virtio/virtio.h"
+#include "hw/virtio/virtio-bus.h"
 #include "exec/address-spaces.h"
 
+static inline AddressSpace *virtio_get_dma_as(VirtIODevice *vdev)
+{
+    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+
+    if (k->get_dma_as) {
+        return k->get_dma_as(qbus->parent);
+    }
+    return &address_space_memory;
+}
+
 static inline bool virtio_access_is_big_endian(VirtIODevice *vdev)
 {
 #if defined(TARGET_IS_BIENDIAN)
@@ -34,45 +46,55 @@ static inline bool virtio_access_is_big_endian(VirtIODevice 
*vdev)
 
 static inline uint16_t virtio_lduw_phys(VirtIODevice *vdev, hwaddr pa)
 {
+    AddressSpace *dma_as = virtio_get_dma_as(vdev);
+
     if (virtio_access_is_big_endian(vdev)) {
-        return lduw_be_phys(&address_space_memory, pa);
+        return lduw_be_phys(dma_as, pa);
     }
-    return lduw_le_phys(&address_space_memory, pa);
+    return lduw_le_phys(dma_as, pa);
 }
 
 static inline uint32_t virtio_ldl_phys(VirtIODevice *vdev, hwaddr pa)
 {
+    AddressSpace *dma_as = virtio_get_dma_as(vdev);
+
     if (virtio_access_is_big_endian(vdev)) {
-        return ldl_be_phys(&address_space_memory, pa);
+        return ldl_be_phys(dma_as, pa);
     }
-    return ldl_le_phys(&address_space_memory, pa);
+    return ldl_le_phys(dma_as, pa);
 }
 
 static inline uint64_t virtio_ldq_phys(VirtIODevice *vdev, hwaddr pa)
 {
+    AddressSpace *dma_as = virtio_get_dma_as(vdev);
+
     if (virtio_access_is_big_endian(vdev)) {
-        return ldq_be_phys(&address_space_memory, pa);
+        return ldq_be_phys(dma_as, pa);
     }
-    return ldq_le_phys(&address_space_memory, pa);
+    return ldq_le_phys(dma_as, pa);
 }
 
 static inline void virtio_stw_phys(VirtIODevice *vdev, hwaddr pa,
                                    uint16_t value)
 {
+    AddressSpace *dma_as = virtio_get_dma_as(vdev);
+
     if (virtio_access_is_big_endian(vdev)) {
-        stw_be_phys(&address_space_memory, pa, value);
+        stw_be_phys(dma_as, pa, value);
     } else {
-        stw_le_phys(&address_space_memory, pa, value);
+        stw_le_phys(dma_as, pa, value);
     }
 }
 
 static inline void virtio_stl_phys(VirtIODevice *vdev, hwaddr pa,
                                    uint32_t value)
 {
+    AddressSpace *dma_as = virtio_get_dma_as(vdev);
+
     if (virtio_access_is_big_endian(vdev)) {
-        stl_be_phys(&address_space_memory, pa, value);
+        stl_be_phys(dma_as, pa, value);
     } else {
-        stl_le_phys(&address_space_memory, pa, value);
+        stl_le_phys(dma_as, pa, value);
     }
 }
 
diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h
index 3f2c136..17c07af 100644
--- a/include/hw/virtio/virtio-bus.h
+++ b/include/hw/virtio/virtio-bus.h
@@ -76,6 +76,7 @@ typedef struct VirtioBusClass {
      * Note that changing this will break migration for this transport.
      */
     bool has_variable_vring_alignment;
+    AddressSpace *(*get_dma_as)(DeviceState *d);
 } VirtioBusClass;
 
 struct VirtioBusState {
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 2b5b248..0908bf6 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -153,9 +153,9 @@ void virtqueue_discard(VirtQueue *vq, const 
VirtQueueElement *elem,
 void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
                     unsigned int len, unsigned int idx);
 
-void virtqueue_map(VirtQueueElement *elem);
+void virtqueue_map(VirtIODevice *vdev, VirtQueueElement *elem);
 void *virtqueue_pop(VirtQueue *vq, size_t sz);
-void *qemu_get_virtqueue_element(QEMUFile *f, size_t sz);
+void *qemu_get_virtqueue_element(VirtIODevice *vdev, QEMUFile *f, size_t sz);
 void qemu_put_virtqueue_element(QEMUFile *f, VirtQueueElement *elem);
 int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes,
                           unsigned int out_bytes);
-- 
2.5.0