Although QEMU virtio is quite fast, there is still some room for
improvements. Disk latency can be reduced if we handle virito-blk
requests
in host kernel istead of passing them to QEMU. The patch adds vhost-blk
kernel module to do so.
Some test setups:
fio --direct=1 --rw=randread --bs=4k --ioengine=libaio --iodepth=128
QEMU drive options: cache=none
filesystem: xfs
SSD:
| randread, IOPS | randwrite, IOPS |
Host | 95.8k | 85.3k |
QEMU virtio | 57.5k | 79.4k |
QEMU vhost-blk | 95.6k | 84.3k |
RAMDISK (vq == vcpu):
| randread, IOPS | randwrite, IOPS |
virtio, 1vcpu | 123k | 129k |
virtio, 2vcpu | 253k (??) | 250k (??) |
virtio, 4vcpu | 158k | 154k |
vhost-blk, 1vcpu | 110k | 113k |
vhost-blk, 2vcpu | 247k | 252k |
vhost-blk, 4vcpu | 576k | 567k |
https://jira.sw.ru/browse/PSBM-139414
Signed-off-by: Andrey Zhadchenko <andrey.zhadche...@virtuozzo.com>
---
v2:
- removed unused VHOST_BLK_VQ
- reworked bio handling a bit: now add all pages from signle iov into
single bio istead of allocating one bio per page
- changed how to calculate sector incrementation
- check move_iovec() in vhost_blk_req_handle()
- remove snprintf check and better check ret from copy_to_iter for
VIRTIO_BLK_ID_BYTES requests
- discard vq request if vhost_blk_req_handle() returned negative code
- forbid to change nonzero backend in vhost_blk_set_backend(). First of
all, QEMU sets backend only once. Also if we want to change backend when
we already running requests we need to be much more careful in
vhost_blk_handle_guest_kick() as it is not taking any references. If
userspace want to change backend that bad it can always reset device.
- removed EXPERIMENTAL from Kconfig
drivers/vhost/Kconfig | 12 +
drivers/vhost/Makefile | 3 +
drivers/vhost/blk.c | 829 +++++++++++++++++++++++++++++++++++++
include/uapi/linux/vhost.h | 5 +
4 files changed, 849 insertions(+)
create mode 100644 drivers/vhost/blk.c
diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 587fbae06182..e1389bf0c10b 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -89,4 +89,16 @@ config VHOST_CROSS_ENDIAN_LEGACY
If unsure, say "N".
+config VHOST_BLK
+ tristate "Host kernel accelerator for virtio-blk"
+ depends on BLOCK && EVENTFD
+ select VHOST
+ default n
+ help
+ This kernel module can be loaded in host kernel to accelerate
+ guest vm with virtio-blk driver.
+
+ To compile this driver as a module, choose M here: the module will
+ be called vhost_blk.
+
endif
diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
index f3e1897cce85..c76cc4f5fcd8 100644
--- a/drivers/vhost/Makefile
+++ b/drivers/vhost/Makefile
@@ -17,3 +17,6 @@ obj-$(CONFIG_VHOST) += vhost.o
obj-$(CONFIG_VHOST_IOTLB) += vhost_iotlb.o
vhost_iotlb-y := iotlb.o
+
+obj-$(CONFIG_VHOST_BLK) += vhost_blk.o
+vhost_blk-y := blk.o
diff --git a/drivers/vhost/blk.c b/drivers/vhost/blk.c
new file mode 100644
index 000000000000..c62b8ae70716
--- /dev/null
+++ b/drivers/vhost/blk.c
@@ -0,0 +1,829 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2011 Taobao, Inc.
+ * Author: Liu Yuan <tailai...@taobao.com>
+ *
+ * Copyright (C) 2012 Red Hat, Inc.
+ * Author: Asias He <as...@redhat.com>
+ *
+ * Copyright (c) 2022 Virtuozzo International GmbH.
+ * Author: Andrey Zhadchenko <andrey.zhadche...@virtuozzo.com>
+ *
+ * virtio-blk host kernel accelerator.
+ */
+
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/vhost.h>
+#include <linux/virtio_blk.h>
+#include <linux/mutex.h>
+#include <linux/file.h>
+#include <linux/kthread.h>
+#include <linux/blkdev.h>
+#include <linux/llist.h>
+
+#include "vhost.h"
+
+enum {
+ VHOST_BLK_FEATURES = VHOST_FEATURES |
+ (1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
+ (1ULL << VIRTIO_RING_F_EVENT_IDX) |
+ (1ULL << VIRTIO_BLK_F_MQ) |
+ (1ULL << VIRTIO_BLK_F_FLUSH),
+};
+
+/*
+ * Max number of bytes transferred before requeueing the job.
+ * Using this limit prevents one virtqueue from starving others.
+ */
+#define VHOST_DEV_WEIGHT 0x80000
+
+/*
+ * Max number of packets transferred before requeueing the job.
+ * Using this limit prevents one virtqueue from starving others with
+ * pkts.
+ */
+#define VHOST_DEV_PKT_WEIGHT 256
+
+#define VHOST_BLK_VQ_MAX 8
+
+#define VHOST_MAX_METADATA_IOV 1
+
+#define VHOST_BLK_SECTOR_BITS 9
+#define VHOST_BLK_SECTOR_SIZE (1 << VHOST_BLK_SECTOR_BITS)
+#define VHOST_BLK_SECTOR_MASK (VHOST_BLK_SECTOR_SIZE - 1)
+
+struct req_page_list {
+ struct page **pages;
+ int pages_nr;
+};
+
+#define NR_INLINE 16
+
+struct vhost_blk_req {
+ struct req_page_list inline_pl[NR_INLINE];
+ struct page *inline_page[NR_INLINE];
+ struct bio *inline_bio[NR_INLINE];
+ struct req_page_list *pl;
+ int during_flush;
+ bool use_inline;
+
+ struct llist_node llnode;
+
+ struct vhost_blk *blk;
+
+ struct iovec *iov;
+ int iov_nr;
+
+ struct bio **bio;
+ atomic_t bio_nr;
+
+ struct iovec status[VHOST_MAX_METADATA_IOV];
+
+ sector_t sector;
+ int bi_opf;
+ u16 head;
+ long len;
+ int bio_err;
+
+ struct vhost_blk_vq *blk_vq;
+};
+
+struct vhost_blk_vq {
+ struct vhost_virtqueue vq;
+ struct vhost_blk_req *req;
+ struct iovec iov[UIO_MAXIOV];
+ struct llist_head llhead;
+ struct vhost_work work;
+};
+
+struct vhost_blk {
+ wait_queue_head_t flush_wait;
+ struct vhost_blk_vq vqs[VHOST_BLK_VQ_MAX];
+ atomic_t req_inflight[2];
+ spinlock_t flush_lock;
+ struct vhost_dev dev;
+ int during_flush;
+ struct file *backend;
+ int index;
+};
+
+static int gen;
+
+static int move_iovec(struct iovec *from, struct iovec *to,
+ size_t len, int iov_count_from, int iov_count_to)
+{
+ int moved_seg = 0, spent_seg = 0;
+ size_t size;
+
+ while (len && spent_seg < iov_count_from && moved_seg <
iov_count_to) {
+ if (from->iov_len == 0) {
+ ++from;
+ ++spent_seg;
+ continue;
+ }
+ size = min(from->iov_len, len);
+ to->iov_base = from->iov_base;
+ to->iov_len = size;
+ from->iov_len -= size;
+ from->iov_base += size;
+ len -= size;
+ ++from;
+ ++to;
+ ++moved_seg;
+ ++spent_seg;
+ }
+
+ return len ? -1 : moved_seg;
+}
+
+static inline int iov_num_pages(struct iovec *iov)
+{
+ return (PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
+ ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
+}
+
+static inline int vhost_blk_set_status(struct vhost_blk_req *req, u8
status)
+{
+ struct iov_iter iter;
+ int ret;
+
+ iov_iter_init(&iter, WRITE, req->status, ARRAY_SIZE(req->status),
sizeof(status));
+ ret = copy_to_iter(&status, sizeof(status), &iter);
+ if (ret != sizeof(status)) {
+ vq_err(&req->blk_vq->vq, "Failed to write status\n");
+ return -EFAULT;
+ }
+
+ return 0;
+}
+
+static void vhost_blk_req_done(struct bio *bio)
+{
+ struct vhost_blk_req *req = bio->bi_private;
+ struct vhost_blk *blk = req->blk;
+
+ req->bio_err = blk_status_to_errno(bio->bi_status);
+
+ if (atomic_dec_and_test(&req->bio_nr)) {
+ llist_add(&req->llnode, &req->blk_vq->llhead);
+ vhost_work_queue(&blk->dev, &req->blk_vq->work);
+ }
+
+ bio_put(bio);
+}
+
+static void vhost_blk_req_umap(struct vhost_blk_req *req)
+{
+ struct req_page_list *pl;
+ int i, j;
+
+ if (req->pl) {
+ for (i = 0; i < req->iov_nr; i++) {
+ pl = &req->pl[i];
+
+ for (j = 0; j < pl->pages_nr; j++) {
+ if (!req->bi_opf)
+ set_page_dirty_lock(pl->pages[j]);
+ put_page(pl->pages[j]);
+ }
+ }
+ }
+
+ if (!req->use_inline)
+ kfree(req->pl);
+}
+
+static int vhost_blk_bio_make_simple(struct vhost_blk_req *req,
+ struct block_device *bdev)
+{
+ struct bio *bio;
+
+ req->use_inline = true;
+ req->pl = NULL;
+ req->bio = req->inline_bio;
+
+ bio = bio_alloc(GFP_KERNEL, 1);
+ if (!bio)
+ return -ENOMEM;
+
+ bio->bi_iter.bi_sector = req->sector;
+ bio_set_dev(bio, bdev);
+ bio->bi_private = req;
+ bio->bi_end_io = vhost_blk_req_done;
+ bio->bi_opf = req->bi_opf;
+ req->bio[0] = bio;
+
+ atomic_set(&req->bio_nr, 1);
+
+ return 0;
+}
+
+static struct page **vhost_blk_prepare_req(struct vhost_blk_req *req,
+ int total_pages, int iov_nr)
+{
+ int pl_len, page_len, bio_len;
+ void *buf;
+
+ req->use_inline = false;
+ pl_len = iov_nr * sizeof(req->pl[0]);
+ page_len = total_pages * sizeof(struct page *);
+ bio_len = total_pages * sizeof(struct bio *);
+
+ buf = kmalloc(pl_len + page_len + bio_len, GFP_KERNEL);
+ if (!buf)
+ return NULL;
+
+ req->pl = buf;
+ req->bio = buf + pl_len + page_len;
+
+ return buf + pl_len;
+}
+
+static int vhost_blk_bio_make(struct vhost_blk_req *req,
+ struct block_device *bdev)
+{
+ int pages_nr_total, i, j, ret;
+ struct iovec *iov = req->iov;
+ int iov_nr = req->iov_nr;
+ struct page **pages, *page;
+ struct bio *bio = NULL;
+ int bio_nr = 0;
+
+ if (unlikely(req->bi_opf == REQ_OP_FLUSH))
+ return vhost_blk_bio_make_simple(req, bdev);
+
+ pages_nr_total = 0;
+ for (i = 0; i < iov_nr; i++)
+ pages_nr_total += iov_num_pages(&iov[i]);
+
+ if (pages_nr_total > NR_INLINE) {
+ pages = vhost_blk_prepare_req(req, pages_nr_total, iov_nr);
+ if (!pages)
+ return -ENOMEM;
+ } else {
+ req->use_inline = true;
+ req->pl = req->inline_pl;
+ pages = req->inline_page;
+ req->bio = req->inline_bio;
+ }
+
+ req->iov_nr = 0;
+ for (i = 0; i < iov_nr; i++) {
+ int pages_nr = iov_num_pages(&iov[i]);
+ unsigned long iov_base, iov_len;
+ struct req_page_list *pl;
+
+ iov_base = (unsigned long)iov[i].iov_base;
+ iov_len = (unsigned long)iov[i].iov_len;
+
+ ret = get_user_pages_fast(iov_base, pages_nr,
+ !req->bi_opf, pages);
+ if (!bio)
+ goto fail;
+ bio->bi_iter.bi_sector = req->sector;
+ bio_set_dev(bio, bdev);
+ bio->bi_private = req;
+ bio->bi_end_io = vhost_blk_req_done;
+ bio->bi_opf = req->bi_opf;
+ req->bio[bio_nr++] = bio;
+
+ for (j = 0; j < pages_nr; j++) {
+ unsigned int off, len, pos;
+
+ page = pages[j];
+ off = iov_base & ~PAGE_MASK;
+ len = PAGE_SIZE - off;
+ if (len > iov_len)
+ len = iov_len;
+
+ if (!bio_add_page(bio, page, len, off))
+ goto fail;
+
+ iov_base += len;
+ iov_len -= len;
+
+ pos = (iov_base & VHOST_BLK_SECTOR_MASK) + iov_len;
+ req->sector += pos >> VHOST_BLK_SECTOR_BITS;
+ }
+
+ pages += pages_nr;
+ }
+ atomic_set(&req->bio_nr, bio_nr);
+ return 0;
+
+fail:
+ for (i = 0; i < bio_nr; i++)
+ bio_put(req->bio[i]);
+ vhost_blk_req_umap(req);
+ return -ENOMEM;
+}
+
+static inline void vhost_blk_bio_send(struct vhost_blk_req *req)
+{
+ struct blk_plug plug;
+ int i, bio_nr;
+
+ bio_nr = atomic_read(&req->bio_nr);
+ blk_start_plug(&plug);
+ for (i = 0; i < bio_nr; i++)
+ submit_bio(req->bio[i]);
+
+ blk_finish_plug(&plug);
+}
+
+static int vhost_blk_req_submit(struct vhost_blk_req *req, struct
file *file)
+{
+
+ struct inode *inode = file->f_mapping->host;
+ struct block_device *bdev = I_BDEV(inode);
+ int ret;
+
+ ret = vhost_blk_bio_make(req, bdev);
+ if (ret < 0)
+ return ret;
+
+ vhost_blk_bio_send(req);
+
+ spin_lock(&req->blk->flush_lock);
+ req->during_flush = req->blk->during_flush;
+ atomic_inc(&req->blk->req_inflight[req->during_flush]);
+ spin_unlock(&req->blk->flush_lock);
+
+ return ret;
+}
+
+static int vhost_blk_req_handle(struct vhost_virtqueue *vq,
+ struct virtio_blk_outhdr *hdr,
+ u16 head, u16 total_iov_nr,
+ struct file *file)
+{
+ struct vhost_blk *blk = container_of(vq->dev, struct vhost_blk,
dev);
+ struct vhost_blk_vq *blk_vq = container_of(vq, struct
vhost_blk_vq, vq);
+ unsigned char id[VIRTIO_BLK_ID_BYTES];
+ struct vhost_blk_req *req;
+ struct iov_iter iter;
+ int ret, len;
+ u8 status;
+
+ req = &blk_vq->req[head];
+ req->blk_vq = blk_vq;
+ req->head = head;
+ req->blk = blk;
+ req->sector = hdr->sector;
+ req->iov = blk_vq->iov;
+
+ req->len = iov_length(vq->iov, total_iov_nr) - sizeof(status);
+ req->iov_nr = move_iovec(vq->iov, req->iov, req->len,
total_iov_nr,
+ ARRAY_SIZE(blk_vq->iov));
+
+ ret = move_iovec(vq->iov, req->status, sizeof(status), total_iov_nr,
+ ARRAY_SIZE(req->status));
+ if (ret < 0 || req->iov_nr < 0)
+ return -EINVAL;
+
+ switch (hdr->type) {
+ case VIRTIO_BLK_T_OUT:
+ req->bi_opf = REQ_OP_WRITE;
+ ret = vhost_blk_req_submit(req, file);
+ break;
+ case VIRTIO_BLK_T_IN:
+ req->bi_opf = REQ_OP_READ;
+ ret = vhost_blk_req_submit(req, file);
+ break;
+ case VIRTIO_BLK_T_FLUSH:
+ req->bi_opf = REQ_OP_FLUSH;
+ ret = vhost_blk_req_submit(req, file);
+ break;
+ case VIRTIO_BLK_T_GET_ID:
+ len = snprintf(id, VIRTIO_BLK_ID_BYTES, "vhost-blk%d",
blk->index);
+ iov_iter_init(&iter, WRITE, req->iov, req->iov_nr, req->len);
+ ret = copy_to_iter(id, len, &iter);
+ status = ret != len ? VIRTIO_BLK_S_IOERR : VIRTIO_BLK_S_OK;
+ ret = vhost_blk_set_status(req, status);
+ if (ret)
+ break;
+ vhost_add_used_and_signal(&blk->dev, vq, head, len);
+ break;
+ default:
+ vq_err(vq, "Unsupported request type %d\n", hdr->type);
+ status = VIRTIO_BLK_S_UNSUPP;
+ ret = vhost_blk_set_status(req, status);
+ if (ret)
+ break;
+ vhost_add_used_and_signal(&blk->dev, vq, head, 0);
+ }
+
+ return ret;
+}
+
+static void vhost_blk_handle_guest_kick(struct vhost_work *work)
+{
+ struct virtio_blk_outhdr hdr;
+ struct vhost_blk_vq *blk_vq;
+ struct vhost_virtqueue *vq;
+ struct iovec hdr_iovec[VHOST_MAX_METADATA_IOV];
+ struct vhost_blk *blk;
+ struct iov_iter iter;
+ int in, out, ret;
+ struct file *f;
+ u16 head;
+
+ vq = container_of(work, struct vhost_virtqueue, poll.work);
+ blk = container_of(vq->dev, struct vhost_blk, dev);
+ blk_vq = container_of(vq, struct vhost_blk_vq, vq);
+
+ f = vhost_vq_get_backend(vq);
+ if (!f)
+ return;
+
+ vhost_disable_notify(&blk->dev, vq);
+ for (;;) {
+ head = vhost_get_vq_desc(vq, vq->iov,
+ ARRAY_SIZE(vq->iov),
+ &out, &in, NULL, NULL);
+ if (unlikely(head < 0))
+ break;
+
+ if (unlikely(head == vq->num)) {
+ if (unlikely(vhost_enable_notify(&blk->dev, vq))) {
+ vhost_disable_notify(&blk->dev, vq);
+ continue;
+ }
+ break;
+ }
+
+ ret = move_iovec(vq->iov, hdr_iovec, sizeof(hdr), in + out,
ARRAY_SIZE(hdr_iovec));
+ if (ret < 0) {
+ vq_err(vq, "virtio_blk_hdr is too split!");
+ vhost_discard_vq_desc(vq, 1);
+ break;
+ }
+
+ iov_iter_init(&iter, READ, hdr_iovec, ARRAY_SIZE(hdr_iovec),
sizeof(hdr));
+ ret = copy_from_iter(&hdr, sizeof(hdr), &iter);
+ if (ret != sizeof(hdr)) {
+ vq_err(vq, "Failed to get block header: read %d bytes
instead of %ld!\n",
+ ret, sizeof(hdr));
+ vhost_discard_vq_desc(vq, 1);
+ break;
+ }
+
+ if (vhost_blk_req_handle(vq, &hdr, head, out + in, f) < 0) {
+ vhost_discard_vq_desc(vq, 1);
+ break;
+ }
+
+ if (!llist_empty(&blk_vq->llhead)) {
+ vhost_poll_queue(&vq->poll);
+ break;
+ }
+ }
+}
+
+static void vhost_blk_handle_host_kick(struct vhost_work *work)
+{
+ struct vhost_blk_vq *blk_vq;
+ struct vhost_virtqueue *vq;
+ struct vhost_blk_req *req;
+ struct llist_node *llnode;
+ struct vhost_blk *blk = NULL;
+ bool added, zero;
+ u8 status;
+ int ret;
+
+ blk_vq = container_of(work, struct vhost_blk_vq, work);
+ vq = &blk_vq->vq;
+ llnode = llist_del_all(&blk_vq->llhead);
+ added = false;
+ while (llnode) {
+ req = llist_entry(llnode, struct vhost_blk_req, llnode);
+ llnode = llist_next(llnode);
+
+ if (!blk)
+ blk = req->blk;
+
+ vhost_blk_req_umap(req);
+
+ status = req->bio_err == 0 ? VIRTIO_BLK_S_OK :
VIRTIO_BLK_S_IOERR;
+ ret = vhost_blk_set_status(req, status);
+ if (unlikely(ret))
+ continue;
+
+ vhost_add_used(vq, req->head, req->len);
+ added = true;
+
+ spin_lock(&req->blk->flush_lock);
+ zero = atomic_dec_and_test(
+ &req->blk->req_inflight[req->during_flush]);
+ if (zero && !req->during_flush)
+ wake_up(&blk->flush_wait);
+ spin_unlock(&req->blk->flush_lock);
+
+ }
+
+ if (likely(added))
+ vhost_signal(&blk->dev, vq);
+}
+
+static void vhost_blk_flush(struct vhost_blk *blk)
+{
+ int i;
+
+ spin_lock(&blk->flush_lock);
+ blk->during_flush = 1;
+ spin_unlock(&blk->flush_lock);
+
+ for (i = 0; i < VHOST_BLK_VQ_MAX; i++)
+ vhost_poll_flush(&blk->vqs[i].vq.poll);
+ vhost_work_dev_flush(&blk->dev);
+ /*
+ * Wait until requests fired before the flush to be finished
+ * req_inflight[0] is used to track the requests fired before the
flush
+ * req_inflight[1] is used to track the requests fired during the
flush
+ */
+ wait_event(blk->flush_wait, !atomic_read(&blk->req_inflight[0]));
+
+ spin_lock(&blk->flush_lock);
+ blk->during_flush = 0;
+ spin_unlock(&blk->flush_lock);
+}
+
+static inline void vhost_blk_drop_backends(struct vhost_blk *blk)
+{
+ struct vhost_virtqueue *vq;
+ int i;
+
+ for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
+ vq = &blk->vqs[i].vq;
+
+ mutex_lock(&vq->mutex);
+ vhost_vq_set_backend(vq, NULL);
+ mutex_unlock(&vq->mutex);
+ }
+}
+
+static int vhost_blk_open(struct inode *inode, struct file *file)
+{
+ struct vhost_blk *blk;
+ struct vhost_virtqueue **vqs;
+ int ret = 0, i = 0;
+
+ blk = kvzalloc(sizeof(*blk), GFP_KERNEL);
+ if (!blk) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ vqs = kcalloc(VHOST_BLK_VQ_MAX, sizeof(*vqs), GFP_KERNEL);
+ if (!vqs) {
+ ret = -ENOMEM;
+ goto out_blk;
+ }
+
+ for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
+ blk->vqs[i].vq.handle_kick = vhost_blk_handle_guest_kick;
+ vqs[i] = &blk->vqs[i].vq;
+ }
+
+ blk->index = gen++;
+
+ atomic_set(&blk->req_inflight[0], 0);
+ atomic_set(&blk->req_inflight[1], 0);
+ blk->during_flush = 0;
+ spin_lock_init(&blk->flush_lock);
+ init_waitqueue_head(&blk->flush_wait);
+
+ vhost_dev_init(&blk->dev, vqs, VHOST_BLK_VQ_MAX, UIO_MAXIOV,
+ VHOST_DEV_WEIGHT, VHOST_DEV_PKT_WEIGHT, true, NULL);
+ file->private_data = blk;
+
+ for (i = 0; i < VHOST_BLK_VQ_MAX; i++)
+ vhost_work_init(&blk->vqs[i].work, vhost_blk_handle_host_kick);
+
+ return ret;
+out_blk:
+ kvfree(blk);
+out:
+ return ret;
+}
+
+static int vhost_blk_release(struct inode *inode, struct file *f)
+{
+ struct vhost_blk *blk = f->private_data;
+ int i;
+
+ vhost_blk_drop_backends(blk);
+ vhost_blk_flush(blk);
+ vhost_dev_stop(&blk->dev);
+ if (blk->backend)
+ fput(blk->backend);
+ vhost_dev_cleanup(&blk->dev);
+ for (i = 0; i < VHOST_BLK_VQ_MAX; i++)
+ kvfree(blk->vqs[i].req);
+ kfree(blk->dev.vqs);
+ kvfree(blk);
+
+ return 0;
+}
+
+static int vhost_blk_set_features(struct vhost_blk *blk, u64 features)
+{
+ struct vhost_virtqueue *vq;
+ int i;
+
+ mutex_lock(&blk->dev.mutex);
+ if ((features & (1 << VHOST_F_LOG_ALL)) &&
+ !vhost_log_access_ok(&blk->dev)) {
+ mutex_unlock(&blk->dev.mutex);
+ return -EFAULT;
+ }
+
+ for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
+ vq = &blk->vqs[i].vq;
+ mutex_lock(&vq->mutex);
+ vq->acked_features = features & (VHOST_BLK_FEATURES);
+ mutex_unlock(&vq->mutex);
+ }
+
+ vhost_blk_flush(blk);
+ mutex_unlock(&blk->dev.mutex);
+
+ return 0;
+}
+
+static long vhost_blk_set_backend(struct vhost_blk *blk, int fd)
+{
+ struct vhost_virtqueue *vq;
+ struct file *file;
+ struct inode *inode;
+ int ret, i;
+
+ mutex_lock(&blk->dev.mutex);
+ ret = vhost_dev_check_owner(&blk->dev);
+ if (ret)
+ goto out_dev;
+
+ if (blk->backend) {
+ ret = -EBUSY;
+ goto out_dev;
+ }
+
+ file = fget(fd);
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ goto out_dev;
+ }
+
+ inode = file->f_mapping->host;
+ if (!S_ISBLK(inode->i_mode)) {
+ ret = -EFAULT;
+ goto out_file;
+ }
+
+ for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
+ vq = &blk->vqs[i].vq;
+ if (!vhost_vq_access_ok(vq)) {
+ ret = -EFAULT;
+ goto out_drop;
+ }
+
+ mutex_lock(&vq->mutex);
+ vhost_vq_set_backend(vq, file);
+ ret = vhost_vq_init_access(vq);
+ mutex_unlock(&vq->mutex);
+ }
+
+ blk->backend = file;
+
+ mutex_unlock(&blk->dev.mutex);
+ return 0;
+
+out_drop:
+ vhost_blk_drop_backends(blk);
+out_file:
+ fput(file);
+out_dev:
+ mutex_unlock(&blk->dev.mutex);
+ return ret;
+}
+
+static long vhost_blk_reset_owner(struct vhost_blk *blk)
+{
+ struct vhost_iotlb *umem;
+ int err, i;
+
+ mutex_lock(&blk->dev.mutex);
+ err = vhost_dev_check_owner(&blk->dev);
+ if (err)
+ goto done;
+ umem = vhost_dev_reset_owner_prepare();
+ if (!umem) {
+ err = -ENOMEM;
+ goto done;
+ }
+ vhost_blk_drop_backends(blk);
+ if (blk->backend) {
+ fput(blk->backend);
+ blk->backend = NULL;
+ }
+ vhost_blk_flush(blk);
+ vhost_dev_stop(&blk->dev);
+ vhost_dev_reset_owner(&blk->dev, umem);
+
+ for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
+ kvfree(blk->vqs[i].req);
+ blk->vqs[i].req = NULL;
+ }
+
+done:
+ mutex_unlock(&blk->dev.mutex);
+ return err;
+}
+
+static int vhost_blk_setup(struct vhost_blk *blk, void __user *argp)
+{
+ struct vhost_vring_state s;
+
+ if (copy_from_user(&s, argp, sizeof(s)))
+ return -EFAULT;
+
+ if (blk->vqs[s.index].req)
+ return 0;
+
+ blk->vqs[s.index].req = kvmalloc(sizeof(struct vhost_blk_req) *
s.num, GFP_KERNEL);
+ if (!blk->vqs[s.index].req)
+ return -ENOMEM;
+
+ return 0;
+}
+
+static long vhost_blk_ioctl(struct file *f, unsigned int ioctl,
+ unsigned long arg)
+{
+ struct vhost_blk *blk = f->private_data;
+ void __user *argp = (void __user *)arg;
+ struct vhost_vring_file backend;
+ u64 __user *featurep = argp;
+ u64 features;
+ int ret;
+
+ switch (ioctl) {
+ case VHOST_BLK_SET_BACKEND:
+ if (copy_from_user(&backend, argp, sizeof(backend)))
+ return -EFAULT;
+ return vhost_blk_set_backend(blk, backend.fd);
+ case VHOST_GET_FEATURES:
+ features = VHOST_BLK_FEATURES;
+ if (copy_to_user(featurep, &features, sizeof(features)))
+ return -EFAULT;
+ return 0;
+ case VHOST_SET_FEATURES:
+ if (copy_from_user(&features, featurep, sizeof(features)))
+ return -EFAULT;
+ if (features & ~VHOST_BLK_FEATURES)
+ return -EOPNOTSUPP;
+ return vhost_blk_set_features(blk, features);
+ case VHOST_RESET_OWNER:
+ return vhost_blk_reset_owner(blk);
+ default:
+ mutex_lock(&blk->dev.mutex);
+ ret = vhost_dev_ioctl(&blk->dev, ioctl, argp);
+ if (ret == -ENOIOCTLCMD)
+ ret = vhost_vring_ioctl(&blk->dev, ioctl, argp);
+ if (!ret && ioctl == VHOST_SET_VRING_NUM)
+ ret = vhost_blk_setup(blk, argp);
+ vhost_blk_flush(blk);
+ mutex_unlock(&blk->dev.mutex);
+ return ret;
+ }
+}
+
+static const struct file_operations vhost_blk_fops = {
+ .owner = THIS_MODULE,
+ .open = vhost_blk_open,
+ .release = vhost_blk_release,
+ .llseek = noop_llseek,
+ .unlocked_ioctl = vhost_blk_ioctl,
+};
+
+static struct miscdevice vhost_blk_misc = {
+ MISC_DYNAMIC_MINOR,
+ "vhost-blk",
+ &vhost_blk_fops,
+};
+module_misc_device(vhost_blk_misc);
+
+MODULE_VERSION("0.0.1");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Andrey Zhadchenko");
+MODULE_DESCRIPTION("Host kernel accelerator for virtio_blk");
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index c998860d7bbc..13caf114bcde 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -150,4 +150,9 @@
/* Get the valid iova range */
#define VHOST_VDPA_GET_IOVA_RANGE _IOR(VHOST_VIRTIO, 0x78, \
struct vhost_vdpa_iova_range)
+
+/* VHOST_BLK specific defines */
+#define VHOST_BLK_SET_BACKEND _IOW(VHOST_VIRTIO, 0xFF, \
+ struct vhost_vring_file)
+
#endif
