Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 327 insertions, 0 deletions

diff --git a/block/null.c b/block/null.c
new file mode 100644
index 000000000..75f7d0db4
--- /dev/null
+++ b/block/null.c
@@ -0,0 +1,327 @@
+/*
+ * Null block driver
+ *
+ * Authors:
+ *  Fam Zheng <famz@redhat.com>
+ *
+ * Copyright (C) 2014 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qstring.h"
+#include "qemu/module.h"
+#include "qemu/option.h"
+#include "block/block_int.h"
+#include "sysemu/replay.h"
+
+#define NULL_OPT_LATENCY "latency-ns"
+#define NULL_OPT_ZEROES  "read-zeroes"
+
+typedef struct {
+    int64_t length;
+    int64_t latency_ns;
+    bool read_zeroes;
+} BDRVNullState;
+
+static QemuOptsList runtime_opts = {
+    .name = "null",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+    .desc = {
+        {
+            .name = BLOCK_OPT_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "size of the null block",
+        },
+        {
+            .name = NULL_OPT_LATENCY,
+            .type = QEMU_OPT_NUMBER,
+            .help = "nanoseconds (approximated) to wait "
+                    "before completing request",
+        },
+        {
+            .name = NULL_OPT_ZEROES,
+            .type = QEMU_OPT_BOOL,
+            .help = "return zeroes when read",
+        },
+        { /* end of list */ }
+    },
+};
+
+static void null_co_parse_filename(const char *filename, QDict *options,
+                                   Error **errp)
+{
+    /* This functions only exists so that a null-co:// filename is accepted
+     * with the null-co driver. */
+    if (strcmp(filename, "null-co://")) {
+        error_setg(errp, "The only allowed filename for this driver is "
+                         "'null-co://'");
+        return;
+    }
+}
+
+static void null_aio_parse_filename(const char *filename, QDict *options,
+                                    Error **errp)
+{
+    /* This functions only exists so that a null-aio:// filename is accepted
+     * with the null-aio driver. */
+    if (strcmp(filename, "null-aio://")) {
+        error_setg(errp, "The only allowed filename for this driver is "
+                         "'null-aio://'");
+        return;
+    }
+}
+
+static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
+                          Error **errp)
+{
+    QemuOpts *opts;
+    BDRVNullState *s = bs->opaque;
+    int ret = 0;
+
+    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &error_abort);
+    s->length =
+        qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30);
+    s->latency_ns =
+        qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0);
+    if (s->latency_ns < 0) {
+        error_setg(errp, "latency-ns is invalid");
+        ret = -EINVAL;
+    }
+    s->read_zeroes = qemu_opt_get_bool(opts, NULL_OPT_ZEROES, false);
+    qemu_opts_del(opts);
+    bs->supported_write_flags = BDRV_REQ_FUA;
+    return ret;
+}
+
+static int64_t null_getlength(BlockDriverState *bs)
+{
+    BDRVNullState *s = bs->opaque;
+    return s->length;
+}
+
+static coroutine_fn int null_co_common(BlockDriverState *bs)
+{
+    BDRVNullState *s = bs->opaque;
+
+    if (s->latency_ns) {
+        qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, s->latency_ns);
+    }
+    return 0;
+}
+
+static coroutine_fn int null_co_preadv(BlockDriverState *bs,
+                                       int64_t offset, int64_t bytes,
+                                       QEMUIOVector *qiov,
+                                       BdrvRequestFlags flags)
+{
+    BDRVNullState *s = bs->opaque;
+
+    if (s->read_zeroes) {
+        qemu_iovec_memset(qiov, 0, 0, bytes);
+    }
+
+    return null_co_common(bs);
+}
+
+static coroutine_fn int null_co_pwritev(BlockDriverState *bs,
+                                        int64_t offset, int64_t bytes,
+                                        QEMUIOVector *qiov,
+                                        BdrvRequestFlags flags)
+{
+    return null_co_common(bs);
+}
+
+static coroutine_fn int null_co_flush(BlockDriverState *bs)
+{
+    return null_co_common(bs);
+}
+
+typedef struct {
+    BlockAIOCB common;
+    QEMUTimer timer;
+} NullAIOCB;
+
+static const AIOCBInfo null_aiocb_info = {
+    .aiocb_size = sizeof(NullAIOCB),
+};
+
+static void null_bh_cb(void *opaque)
+{
+    NullAIOCB *acb = opaque;
+    acb->common.cb(acb->common.opaque, 0);
+    qemu_aio_unref(acb);
+}
+
+static void null_timer_cb(void *opaque)
+{
+    NullAIOCB *acb = opaque;
+    acb->common.cb(acb->common.opaque, 0);
+    timer_deinit(&acb->timer);
+    qemu_aio_unref(acb);
+}
+
+static inline BlockAIOCB *null_aio_common(BlockDriverState *bs,
+                                          BlockCompletionFunc *cb,
+                                          void *opaque)
+{
+    NullAIOCB *acb;
+    BDRVNullState *s = bs->opaque;
+
+    acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
+    /* Only emulate latency after vcpu is running. */
+    if (s->latency_ns) {
+        aio_timer_init(bdrv_get_aio_context(bs), &acb->timer,
+                       QEMU_CLOCK_REALTIME, SCALE_NS,
+                       null_timer_cb, acb);
+        timer_mod_ns(&acb->timer,
+                     qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + s->latency_ns);
+    } else {
+        replay_bh_schedule_oneshot_event(bdrv_get_aio_context(bs),
+                                         null_bh_cb, acb);
+    }
+    return &acb->common;
+}
+
+static BlockAIOCB *null_aio_preadv(BlockDriverState *bs,
+                                   int64_t offset, int64_t bytes,
+                                   QEMUIOVector *qiov, BdrvRequestFlags flags,
+                                   BlockCompletionFunc *cb,
+                                   void *opaque)
+{
+    BDRVNullState *s = bs->opaque;
+
+    if (s->read_zeroes) {
+        qemu_iovec_memset(qiov, 0, 0, bytes);
+    }
+
+    return null_aio_common(bs, cb, opaque);
+}
+
+static BlockAIOCB *null_aio_pwritev(BlockDriverState *bs,
+                                    int64_t offset, int64_t bytes,
+                                    QEMUIOVector *qiov, BdrvRequestFlags flags,
+                                    BlockCompletionFunc *cb,
+                                    void *opaque)
+{
+    return null_aio_common(bs, cb, opaque);
+}
+
+static BlockAIOCB *null_aio_flush(BlockDriverState *bs,
+                                  BlockCompletionFunc *cb,
+                                  void *opaque)
+{
+    return null_aio_common(bs, cb, opaque);
+}
+
+static int null_reopen_prepare(BDRVReopenState *reopen_state,
+                               BlockReopenQueue *queue, Error **errp)
+{
+    return 0;
+}
+
+static int coroutine_fn null_co_block_status(BlockDriverState *bs,
+                                             bool want_zero, int64_t offset,
+                                             int64_t bytes, int64_t *pnum,
+                                             int64_t *map,
+                                             BlockDriverState **file)
+{
+    BDRVNullState *s = bs->opaque;
+    int ret = BDRV_BLOCK_OFFSET_VALID;
+
+    *pnum = bytes;
+    *map = offset;
+    *file = bs;
+
+    if (s->read_zeroes) {
+        ret |= BDRV_BLOCK_ZERO;
+    }
+    return ret;
+}
+
+static void null_refresh_filename(BlockDriverState *bs)
+{
+    const QDictEntry *e;
+
+    for (e = qdict_first(bs->full_open_options); e;
+         e = qdict_next(bs->full_open_options, e))
+    {
+        /* These options can be ignored */
+        if (strcmp(qdict_entry_key(e), "filename") &&
+            strcmp(qdict_entry_key(e), "driver") &&
+            strcmp(qdict_entry_key(e), NULL_OPT_LATENCY))
+        {
+            return;
+        }
+    }
+
+    snprintf(bs->exact_filename, sizeof(bs->exact_filename), "%s://",
+             bs->drv->format_name);
+}
+
+static int64_t null_allocated_file_size(BlockDriverState *bs)
+{
+    return 0;
+}
+
+static const char *const null_strong_runtime_opts[] = {
+    BLOCK_OPT_SIZE,
+    NULL_OPT_ZEROES,
+
+    NULL
+};
+
+static BlockDriver bdrv_null_co = {
+    .format_name            = "null-co",
+    .protocol_name          = "null-co",
+    .instance_size          = sizeof(BDRVNullState),
+
+    .bdrv_file_open         = null_file_open,
+    .bdrv_parse_filename    = null_co_parse_filename,
+    .bdrv_getlength         = null_getlength,
+    .bdrv_get_allocated_file_size = null_allocated_file_size,
+
+    .bdrv_co_preadv         = null_co_preadv,
+    .bdrv_co_pwritev        = null_co_pwritev,
+    .bdrv_co_flush_to_disk  = null_co_flush,
+    .bdrv_reopen_prepare    = null_reopen_prepare,
+
+    .bdrv_co_block_status   = null_co_block_status,
+
+    .bdrv_refresh_filename  = null_refresh_filename,
+    .strong_runtime_opts    = null_strong_runtime_opts,
+};
+
+static BlockDriver bdrv_null_aio = {
+    .format_name            = "null-aio",
+    .protocol_name          = "null-aio",
+    .instance_size          = sizeof(BDRVNullState),
+
+    .bdrv_file_open         = null_file_open,
+    .bdrv_parse_filename    = null_aio_parse_filename,
+    .bdrv_getlength         = null_getlength,
+    .bdrv_get_allocated_file_size = null_allocated_file_size,
+
+    .bdrv_aio_preadv        = null_aio_preadv,
+    .bdrv_aio_pwritev       = null_aio_pwritev,
+    .bdrv_aio_flush         = null_aio_flush,
+    .bdrv_reopen_prepare    = null_reopen_prepare,
+
+    .bdrv_co_block_status   = null_co_block_status,
+
+    .bdrv_refresh_filename  = null_refresh_filename,
+    .strong_runtime_opts    = null_strong_runtime_opts,
+};
+
+static void bdrv_null_init(void)
+{
+    bdrv_register(&bdrv_null_co);
+    bdrv_register(&bdrv_null_aio);
+}
+
+block_init(bdrv_null_init);