Add virtio-blk support

Virtio-blk is a paravirtual block device based on VirtIO.  It can be used by
specifying the if=virtio parameter to the -drive parameter.

When using -enable-kvm, it can achieve very good performance compared to IDE or
SCSI.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5870 c046a42c-6fe2-441c-8c8c-71466251a162

hw/virtio-blk.c

@@ -0,0 +1,248 @@
+/*
+ * Virtio Block Device
+ *
+ * Copyright IBM, Corp. 2007
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "virtio-blk.h"
+#include "block_int.h"
+
+typedef struct VirtIOBlock
+{
+    VirtIODevice vdev;
+    BlockDriverState *bs;
+    VirtQueue *vq;
+} VirtIOBlock;
+
+static VirtIOBlock *to_virtio_blk(VirtIODevice *vdev)
+{
+    return (VirtIOBlock *)vdev;
+}
+
+typedef struct VirtIOBlockReq
+{
+    VirtIOBlock *dev;
+    VirtQueueElement elem;
+    struct virtio_blk_inhdr *in;
+    struct virtio_blk_outhdr *out;
+    size_t size;
+    uint8_t *buffer;
+} VirtIOBlockReq;
+
+static void virtio_blk_rw_complete(void *opaque, int ret)
+{
+    VirtIOBlockReq *req = opaque;
+    VirtIOBlock *s = req->dev;
+
+    /* Copy read data to the guest */
+    if (!ret && !(req->out->type & VIRTIO_BLK_T_OUT)) {
+        size_t offset = 0;
+        int i;
+
+        for (i = 0; i < req->elem.in_num - 1; i++) {
+            size_t len;
+
+            /* Be pretty defensive wrt malicious guests */
+            len = MIN(req->elem.in_sg[i].iov_len,
+                      req->size - offset);
+
+            memcpy(req->elem.in_sg[i].iov_base,
+                   req->buffer + offset,
+                   len);
+            offset += len;
+        }
+    }
+
+    req->in->status = ret ? VIRTIO_BLK_S_IOERR : VIRTIO_BLK_S_OK;
+    virtqueue_push(s->vq, &req->elem, req->size + sizeof(*req->in));
+    virtio_notify(&s->vdev, s->vq);
+
+    qemu_free(req->buffer);
+    qemu_free(req);
+}
+
+static VirtIOBlockReq *virtio_blk_get_request(VirtIOBlock *s)
+{
+    VirtIOBlockReq *req;
+
+    req = qemu_mallocz(sizeof(*req));
+    if (req == NULL)
+        return NULL;
+
+    req->dev = s;
+    if (!virtqueue_pop(s->vq, &req->elem)) {
+        qemu_free(req);
+        return NULL;
+    }
+
+    return req;
+}
+
+static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
+{
+    VirtIOBlock *s = to_virtio_blk(vdev);
+    VirtIOBlockReq *req;
+
+    while ((req = virtio_blk_get_request(s))) {
+        int i;
+
+        if (req->elem.out_num < 1 || req->elem.in_num < 1) {
+            fprintf(stderr, "virtio-blk missing headers\n");
+            exit(1);
+        }
+
+        if (req->elem.out_sg[0].iov_len < sizeof(*req->out) ||
+            req->elem.in_sg[req->elem.in_num - 1].iov_len < sizeof(*req->in)) {
+            fprintf(stderr, "virtio-blk header not in correct element\n");
+            exit(1);
+        }
+
+        req->out = (void *)req->elem.out_sg[0].iov_base;
+        req->in = (void *)req->elem.in_sg[req->elem.in_num - 1].iov_base;
+
+        if (req->out->type & VIRTIO_BLK_T_SCSI_CMD) {
+            unsigned int len = sizeof(*req->in);
+
+            req->in->status = VIRTIO_BLK_S_UNSUPP;
+            virtqueue_push(vq, &req->elem, len);
+            virtio_notify(vdev, vq);
+            qemu_free(req);
+        } else if (req->out->type & VIRTIO_BLK_T_OUT) {
+            size_t offset;
+
+            for (i = 1; i < req->elem.out_num; i++)
+                req->size += req->elem.out_sg[i].iov_len;
+
+            req->buffer = qemu_memalign(512, req->size);
+            if (req->buffer == NULL) {
+                qemu_free(req);
+                break;
+            }
+
+            /* We copy the data from the SG list to avoid splitting up the request.  This helps
+               performance a lot until we can pass full sg lists as AIO operations */
+            offset = 0;
+            for (i = 1; i < req->elem.out_num; i++) {
+                size_t len;
+
+                len = MIN(req->elem.out_sg[i].iov_len,
+                          req->size - offset);
+                memcpy(req->buffer + offset,
+                       req->elem.out_sg[i].iov_base,
+                       len);
+                offset += len;
+            }
+
+            bdrv_aio_write(s->bs, req->out->sector,
+                           req->buffer,
+                           req->size / 512,
+                           virtio_blk_rw_complete,
+                           req);
+        } else {
+            for (i = 0; i < req->elem.in_num - 1; i++)
+                req->size += req->elem.in_sg[i].iov_len;
+
+            req->buffer = qemu_memalign(512, req->size);
+            if (req->buffer == NULL) {
+                qemu_free(req);
+                break;
+            }
+
+            bdrv_aio_read(s->bs, req->out->sector,
+                          req->buffer,
+                          req->size / 512,
+                          virtio_blk_rw_complete,
+                          req);
+        }
+    }
+    /*
+     * FIXME: Want to check for completions before returning to guest mode,
+     * so cached reads and writes are reported as quickly as possible. But
+     * that should be done in the generic block layer.
+     */
+}
+
+static void virtio_blk_reset(VirtIODevice *vdev)
+{
+    /*
+     * This should cancel pending requests, but can't do nicely until there
+     * are per-device request lists.
+     */
+    qemu_aio_flush();
+}
+
+static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
+{
+    VirtIOBlock *s = to_virtio_blk(vdev);
+    struct virtio_blk_config blkcfg;
+    uint64_t capacity;
+    int cylinders, heads, secs;
+
+    bdrv_get_geometry(s->bs, &capacity);
+    bdrv_get_geometry_hint(s->bs, &cylinders, &heads, &secs);
+    stq_raw(&blkcfg.capacity, capacity);
+    stl_raw(&blkcfg.seg_max, 128 - 2);
+    stw_raw(&blkcfg.cylinders, cylinders);
+    blkcfg.heads = heads;
+    blkcfg.sectors = secs;
+    memcpy(config, &blkcfg, sizeof(blkcfg));
+}
+
+static uint32_t virtio_blk_get_features(VirtIODevice *vdev)
+{
+    return (1 << VIRTIO_BLK_F_SEG_MAX | 1 << VIRTIO_BLK_F_GEOMETRY);
+}
+
+static void virtio_blk_save(QEMUFile *f, void *opaque)
+{
+    VirtIOBlock *s = opaque;
+    virtio_save(&s->vdev, f);
+}
+
+static int virtio_blk_load(QEMUFile *f, void *opaque, int version_id)
+{
+    VirtIOBlock *s = opaque;
+
+    if (version_id != 1)
+        return -EINVAL;
+
+    virtio_load(&s->vdev, f);
+
+    return 0;
+}
+
+void *virtio_blk_init(PCIBus *bus, uint16_t vendor, uint16_t device,
+                      BlockDriverState *bs)
+{
+    VirtIOBlock *s;
+    int cylinders, heads, secs;
+    static int virtio_blk_id;
+
+    s = (VirtIOBlock *)virtio_init_pci(bus, "virtio-blk", vendor, device,
+                                       0, VIRTIO_ID_BLOCK,
+                                       0x01, 0x80, 0x00,
+                                       sizeof(struct virtio_blk_config), sizeof(VirtIOBlock));
+    if (!s)
+        return NULL;
+
+    s->vdev.get_config = virtio_blk_update_config;
+    s->vdev.get_features = virtio_blk_get_features;
+    s->vdev.reset = virtio_blk_reset;
+    s->bs = bs;
+    bdrv_guess_geometry(s->bs, &cylinders, &heads, &secs);
+    bdrv_set_geometry_hint(s->bs, cylinders, heads, secs);
+
+    s->vq = virtio_add_queue(&s->vdev, 128, virtio_blk_handle_output);
+
+    register_savevm("virtio-blk", virtio_blk_id++, 1,
+                    virtio_blk_save, virtio_blk_load, s);
+
+    return s;
+}