On Mon, Jul 25, 2022 at 11:27:53PM +0300, Andrey Zhadchenko wrote: > 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 | > > Signed-off-by: Andrey Zhadchenko <[email protected]>
Sounds good to me. What this depends on is whether some userspace will actually use it. In the past QEMU rejected support for vhost-blk, if this time it fares better then I won't have a problem merging the kernel bits. > --- > drivers/vhost/Kconfig | 12 + > drivers/vhost/Makefile | 3 + > drivers/vhost/blk.c | 831 +++++++++++++++++++++++++++++++++++++ > include/uapi/linux/vhost.h | 4 + > 4 files changed, 850 insertions(+) > create mode 100644 drivers/vhost/blk.c > > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig > index 587fbae06182..bcd21a434885 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 (EXPERIMENTAL)" > + 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..2c3cda47b54f > --- /dev/null > +++ b/drivers/vhost/blk.c > @@ -0,0 +1,831 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright (C) 2011 Taobao, Inc. > + * Author: Liu Yuan <[email protected]> > + * > + * Copyright (C) 2012 Red Hat, Inc. > + * Author: Asias He <[email protected]> > + * > + * Copyright (c) 2022 Virtuozzo International GmbH. > + * Author: Andrey Zhadchenko <[email protected]> > + * > + * 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 > + > +enum { > + VHOST_BLK_VQ = 0, > + VHOST_BLK_VQ_MAX = 8, > +}; > + > +#define VHOST_MAX_METADATA_IOV 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 (ret != pages_nr) > + goto fail; > + > + req->iov_nr++; > + pl = &req->pl[i]; > + pl->pages_nr = pages_nr; > + pl->pages = pages; > + > + for (j = 0; j < pages_nr; j++) { > + unsigned int off, len; > + > + page = pages[j]; > + off = iov_base & ~PAGE_MASK; > + len = PAGE_SIZE - off; > + if (len > iov_len) > + len = iov_len; > + > + bio = bio_alloc(GFP_KERNEL, 1); > + 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; > + bio_add_page(bio, page, len, off); > + req->sector += len >> 9; > + iov_base += len; > + iov_len -= len; > + } > + > + 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)); > + > + move_iovec(vq->iov, req->status, sizeof(status), total_iov_nr, > ARRAY_SIZE(req->status)); > + if (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: > + ret = snprintf(id, VIRTIO_BLK_ID_BYTES, > + "vhost-blk%d", blk->index); > + if (ret < 0) > + break; > + len = ret; > + iov_iter_init(&iter, WRITE, req->iov, req->iov_nr, req->len); > + ret = copy_to_iter(id, len, &iter); > + status = ret < 0 ? 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) > + 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, *oldfile = NULL; > + struct inode *inode; > + int ret, i; > + > + mutex_lock(&blk->dev.mutex); > + ret = vhost_dev_check_owner(&blk->dev); > + if (ret) > + goto out_dev; > + > + file = fget(fd); > + if (IS_ERR(file)) { > + ret = PTR_ERR(file); > + goto out_dev; > + } > + > + if (file == blk->backend) { > + fput(file); > + goto out_dev; > + } > + > + oldfile = blk->backend; > + blk->backend = file; > + > + 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); > + } > + > + if (oldfile) { > + vhost_blk_flush(blk); > + fput(oldfile); > + } > + > + mutex_unlock(&blk->dev.mutex); > + return 0; > + > +out_drop: > + vhost_blk_drop_backends(blk); > +out_file: > + fput(file); > + blk->backend = NULL; > +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 cab645d4a645..a54861e9633e 100644 > --- a/include/uapi/linux/vhost.h > +++ b/include/uapi/linux/vhost.h > @@ -171,4 +171,8 @@ > #define VHOST_VDPA_SET_GROUP_ASID _IOW(VHOST_VIRTIO, 0x7C, \ > struct vhost_vring_state) > > +/* VHOST_BLK specific defines */ > +#define VHOST_BLK_SET_BACKEND _IOW(VHOST_VIRTIO, 0x90, \ > + struct vhost_vring_file) > + > #endif > -- > 2.31.1 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
