The virtio-blk-data-plane feature is easy to integrate into
hw/virtio-blk.c. The data plane can be started and stopped similar to
vhost-net.
Users can take advantage of the virtio-blk-data-plane feature using the
new -device virtio-blk-pci,x-data-plane=on property.
The x-data-plane name was chosen because at this stage the feature is
experimental and likely to see changes in the future.
If the VM configuration does not support virtio-blk-data-plane an error
message is printed. Although we could fall back to regular virtio-blk,
I prefer the explicit approach since it prompts the user to fix their
configuration if they want the performance benefit of
virtio-blk-data-plane.
Limitations:
* Only format=raw is supported
* Live migration is not supported
* Block jobs, hot unplug, and other operations fail with -EBUSY
* I/O throttling limits are ignored
* Only Linux hosts are supported due to Linux AIO usage
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
hw/virtio-blk.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
hw/virtio-pci.c | 3 +++
2 files changed, 46 insertions(+), 1 deletion(-)
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index fabf387..538a0ae 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -17,6 +17,9 @@
#include "hw/block-common.h"
#include "blockdev.h"
#include "virtio-blk.h"
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+#include "hw/dataplane/virtio-blk.h"
+#endif
#include "scsi-defs.h"
#ifdef __linux__
# include <scsi/sg.h>
@@ -33,6 +36,9 @@ typedef struct VirtIOBlock
VirtIOBlkConf *blk;
unsigned short sector_mask;
DeviceState *qdev;
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+ VirtIOBlockDataPlane *dataplane;
+#endif
} VirtIOBlock;
static VirtIOBlock *to_virtio_blk(VirtIODevice *vdev)
@@ -407,6 +413,16 @@ static void virtio_blk_handle_output(VirtIODevice *vdev,
VirtQueue *vq)
.num_writes = 0,
};
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+ /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
+ * dataplane here instead of waiting for .set_status().
+ */
+ if (s->dataplane) {
+ virtio_blk_data_plane_start(s->dataplane);
+ return;
+ }
+#endif
+
while ((req = virtio_blk_get_request(s))) {
virtio_blk_handle_request(req, &mrb);
}
@@ -446,8 +462,9 @@ static void virtio_blk_dma_restart_cb(void *opaque, int
running,
{
VirtIOBlock *s = opaque;
- if (!running)
+ if (!running) {
return;
+ }
if (!s->bh) {
s->bh = qemu_bh_new(virtio_blk_dma_restart_bh, s);
@@ -457,6 +474,14 @@ static void virtio_blk_dma_restart_cb(void *opaque, int
running,
static void virtio_blk_reset(VirtIODevice *vdev)
{
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+ VirtIOBlock *s = to_virtio_blk(vdev);
+
+ if (s->dataplane) {
+ virtio_blk_data_plane_stop(s->dataplane);
+ }
+#endif
+
/*
* This should cancel pending requests, but can't do nicely until there
* are per-device request lists.
@@ -541,6 +566,12 @@ static void virtio_blk_set_status(VirtIODevice *vdev,
uint8_t status)
VirtIOBlock *s = to_virtio_blk(vdev);
uint32_t features;
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+ if (s->dataplane && !(status & VIRTIO_CONFIG_S_DRIVER)) {
+ virtio_blk_data_plane_stop(s->dataplane);
+ }
+#endif
+
if (!(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
return;
}
@@ -638,6 +669,12 @@ VirtIODevice *virtio_blk_init(DeviceState *dev,
VirtIOBlkConf *blk)
s->sector_mask = (s->conf->logical_block_size / BDRV_SECTOR_SIZE) - 1;
s->vq = virtio_add_queue(&s->vdev, 128, virtio_blk_handle_output);
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+ if (!virtio_blk_data_plane_create(&s->vdev, blk, &s->dataplane)) {
+ virtio_cleanup(&s->vdev);
+ return NULL;
+ }
+#endif
qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
s->qdev = dev;
@@ -655,6 +692,11 @@ VirtIODevice *virtio_blk_init(DeviceState *dev,
VirtIOBlkConf *blk)
void virtio_blk_exit(VirtIODevice *vdev)
{
VirtIOBlock *s = to_virtio_blk(vdev);
+
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+ virtio_blk_data_plane_destroy(s->dataplane);
+ s->dataplane = NULL;
+#endif
unregister_savevm(s->qdev, "virtio-blk", s);
blockdev_mark_auto_del(s->bs);
virtio_cleanup(vdev);
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 71f4fb5..32cc910 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -897,6 +897,9 @@ static Property virtio_blk_properties[] = {
#endif
DEFINE_PROP_BIT("config-wce", VirtIOPCIProxy, blk.config_wce, 0, true),
DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+ DEFINE_PROP_BIT("x-data-plane", VirtIOPCIProxy, blk.data_plane, 0, false),
+#endif
DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
DEFINE_VIRTIO_BLK_FEATURES(VirtIOPCIProxy, host_features),
DEFINE_PROP_END_OF_LIST(),
--
1.8.0.2
