The 'zeroes-co' block driver is almost a copy of the 'null-co'
block driver designed for performance testing, but targets
security needs, by always zero-initializing read accesses.
Write accesses are discarded.
Suggested-by: Fam Zheng <f...@euphon.net>
Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com>
---
block/zeroes.c | 306 ++++++++++++++++++++++++++++++++++++++++++++++
block/meson.build | 1 +
2 files changed, 307 insertions(+)
create mode 100644 block/zeroes.c
diff --git a/block/zeroes.c b/block/zeroes.c
new file mode 100644
index 00000000000..7256b6d02ee
--- /dev/null
+++ b/block/zeroes.c
@@ -0,0 +1,306 @@
+/*
+ * Zeroes block driver
+ *
+ * Based on block/null.c
+ *
+ * Copyright (C) 2021 Red Hat, Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#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"
+
+typedef struct {
+ int64_t length;
+ int64_t latency_ns;
+} BDRVZeroesState;
+
+static QemuOptsList runtime_opts = {
+ .name = "zeroes",
+ .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+ .desc = {
+ {
+ .name = BLOCK_OPT_SIZE,
+ .type = QEMU_OPT_SIZE,
+ .help = "size of the zeroes block",
+ },
+ {
+ .name = NULL_OPT_LATENCY,
+ .type = QEMU_OPT_NUMBER,
+ .help = "nanoseconds (approximated) to wait "
+ "before completing request",
+ },
+ { /* end of list */ }
+ },
+};
+
+static void zeroes_co_parse_filename(const char *filename, QDict *options,
+ Error **errp)
+{
+ /*
+ * This functions only exists so that a zeroes-co:// filename
+ * is accepted with the zeroes-co driver.
+ */
+ if (strcmp(filename, "zeroes-co://")) {
+ error_setg(errp, "The only allowed filename for this driver is "
+ "'zeroes-co://'");
+ return;
+ }
+}
+
+static void zeroes_aio_parse_filename(const char *filename, QDict *options,
+ Error **errp)
+{
+ /*
+ * This functions only exists so that a zeroes-aio:// filename
+ * is accepted with the zeroes-aio driver.
+ */
+ if (strcmp(filename, "zeroes-aio://")) {
+ error_setg(errp, "The only allowed filename for this driver is "
+ "'zeroes-aio://'");
+ return;
+ }
+}
+
+static int zeroes_file_open(BlockDriverState *bs, QDict *options,
+ int flags, Error **errp)
+{
+ QemuOpts *opts;
+ BDRVZeroesState *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, 0);
+ if (s->length < 0) {
+ error_setg(errp, "%s is invalid", BLOCK_OPT_SIZE);
+ ret = -EINVAL;
+ }
+ s->latency_ns = qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0);
+ if (s->latency_ns < 0) {
+ error_setg(errp, "%s is invalid", NULL_OPT_LATENCY);
+ ret = -EINVAL;
+ }
+ qemu_opts_del(opts);
+ bs->supported_write_flags = BDRV_REQ_FUA;
+ return ret;
+}
+
+static int64_t zeroes_getlength(BlockDriverState *bs)
+{
+ BDRVZeroesState *s = bs->opaque;
+ return s->length;
+}
+
+static coroutine_fn int zeroes_co_common(BlockDriverState *bs)
+{
+ BDRVZeroesState *s = bs->opaque;
+
+ if (s->latency_ns) {
+ qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, s->latency_ns);
+ }
+ return 0;
+}
+
+static coroutine_fn int zeroes_co_preadv(BlockDriverState *bs,
+ uint64_t offset, uint64_t bytes,
+ QEMUIOVector *qiov, int flags)
+{
+ qemu_iovec_memset(qiov, 0, 0, bytes);
+
+ return zeroes_co_common(bs);
+}
+
+static coroutine_fn int zeroes_co_pwritev(BlockDriverState *bs,
+ uint64_t offset, uint64_t bytes,
+ QEMUIOVector *qiov, int flags)
+{
+ return zeroes_co_common(bs);
+}
+
+static coroutine_fn int zeroes_co_flush(BlockDriverState *bs)
+{
+ return zeroes_co_common(bs);
+}
+
+typedef struct {
+ BlockAIOCB common;
+ QEMUTimer timer;
+} ZeroesAIOCB;
+
+static const AIOCBInfo zeroes_aiocb_info = {
+ .aiocb_size = sizeof(ZeroesAIOCB),
+};
+
+static void zeroes_bh_cb(void *opaque)
+{
+ ZeroesAIOCB *acb = opaque;
+ acb->common.cb(acb->common.opaque, 0);
+ qemu_aio_unref(acb);
+}
+
+static void zeroes_timer_cb(void *opaque)
+{
+ ZeroesAIOCB *acb = opaque;
+ acb->common.cb(acb->common.opaque, 0);
+ timer_deinit(&acb->timer);
+ qemu_aio_unref(acb);
+}
+
+static inline BlockAIOCB *zeroes_aio_common(BlockDriverState *bs,
+ BlockCompletionFunc *cb,
+ void *opaque)
+{
+ ZeroesAIOCB *acb;
+ BDRVZeroesState *s = bs->opaque;
+
+ acb = qemu_aio_get(&zeroes_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,
+ zeroes_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),
+ zeroes_bh_cb, acb);
+ }
+ return &acb->common;
+}
+
+static BlockAIOCB *zeroes_aio_preadv(BlockDriverState *bs,
+ uint64_t offset, uint64_t bytes,
+ QEMUIOVector *qiov, int flags,
+ BlockCompletionFunc *cb,
+ void *opaque)
+{
+ qemu_iovec_memset(qiov, 0, 0, bytes);
+
+ return zeroes_aio_common(bs, cb, opaque);
+}
+
+static BlockAIOCB *zeroes_aio_pwritev(BlockDriverState *bs,
+ uint64_t offset, uint64_t bytes,
+ QEMUIOVector *qiov, int flags,
+ BlockCompletionFunc *cb,
+ void *opaque)
+{
+ return zeroes_aio_common(bs, cb, opaque);
+}
+
+static BlockAIOCB *zeroes_aio_flush(BlockDriverState *bs,
+ BlockCompletionFunc *cb,
+ void *opaque)
+{
+ return zeroes_aio_common(bs, cb, opaque);
+}
+
+static int zeroes_reopen_prepare(BDRVReopenState *reopen_state,
+ BlockReopenQueue *queue, Error **errp)
+{
+ return 0;
+}
+
+static int coroutine_fn zeroes_co_block_status(BlockDriverState *bs,
+ bool want_zero, int64_t offset,
+ int64_t bytes, int64_t *pnum,
+ int64_t *map,
+ BlockDriverState **file)
+{
+ *pnum = bytes;
+ *map = offset;
+ *file = bs;
+
+ return BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_ZERO;
+}
+
+static void zeroes_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 zeroes_allocated_file_size(BlockDriverState *bs)
+{
+ return 0;
+}
+
+static const char *const zeroes_strong_runtime_opts[] = {
+ BLOCK_OPT_SIZE,
+
+ NULL
+};
+
+static BlockDriver bdrv_zeroes_co = {
+ .format_name = "zeroes-co",
+ .protocol_name = "zeroes-co",
+ .instance_size = sizeof(BDRVZeroesState),
+
+ .bdrv_file_open = zeroes_file_open,
+ .bdrv_parse_filename = zeroes_co_parse_filename,
+ .bdrv_getlength = zeroes_getlength,
+ .bdrv_get_allocated_file_size = zeroes_allocated_file_size,
+
+ .bdrv_co_preadv = zeroes_co_preadv,
+ .bdrv_co_pwritev = zeroes_co_pwritev,
+ .bdrv_co_flush_to_disk = zeroes_co_flush,
+ .bdrv_reopen_prepare = zeroes_reopen_prepare,
+
+ .bdrv_co_block_status = zeroes_co_block_status,
+
+ .bdrv_refresh_filename = zeroes_refresh_filename,
+ .strong_runtime_opts = zeroes_strong_runtime_opts,
+};
+
+static BlockDriver bdrv_zeroes_aio = {
+ .format_name = "zeroes-aio",
+ .protocol_name = "zeroes-aio",
+ .instance_size = sizeof(BDRVZeroesState),
+
+ .bdrv_file_open = zeroes_file_open,
+ .bdrv_parse_filename = zeroes_aio_parse_filename,
+ .bdrv_getlength = zeroes_getlength,
+ .bdrv_get_allocated_file_size = zeroes_allocated_file_size,
+
+ .bdrv_aio_preadv = zeroes_aio_preadv,
+ .bdrv_aio_pwritev = zeroes_aio_pwritev,
+ .bdrv_aio_flush = zeroes_aio_flush,
+ .bdrv_reopen_prepare = zeroes_reopen_prepare,
+
+ .bdrv_co_block_status = zeroes_co_block_status,
+
+ .bdrv_refresh_filename = zeroes_refresh_filename,
+ .strong_runtime_opts = zeroes_strong_runtime_opts,
+};
+
+static void bdrv_zeroes_init(void)
+{
+ bdrv_register(&bdrv_zeroes_co);
+ bdrv_register(&bdrv_zeroes_aio);
+}
+
+block_init(bdrv_zeroes_init);
diff --git a/block/meson.build b/block/meson.build
index d21990ec95a..661d84118fb 100644
--- a/block/meson.build
+++ b/block/meson.build
@@ -40,6 +40,7 @@
'vmdk.c',
'vpc.c',
'write-threshold.c',
+ 'zeroes.c',
), zstd, zlib, gnutls)
softmmu_ss.add(when: 'CONFIG_TCG', if_true: files('blkreplay.c'))
--
2.26.2
