[Devel] [PATCH RH9 v2 01/10] drivers/vhost: vhost-blk accelerator for virtio-blk guests
Pavel Tikhomirov
ptikhomirov at virtuozzo.com
Thu Sep 15 18:01:58 MSK 2022
On 08.09.2022 18:32, 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 |
>
> https://jira.sw.ru/browse/PSBM-139414
> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at 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.ly at taobao.com>
> + *
> + * Copyright (C) 2012 Red Hat, Inc.
> + * Author: Asias He <asias at redhat.com>
> + *
> + * Copyright (c) 2022 Virtuozzo International GmbH.
> + * Author: Andrey Zhadchenko <andrey.zhadchenko at 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 (ret != pages_nr)
> + goto fail;
> +
> + req->iov_nr++;
> + pl = &req->pl[i];
> + pl->pages_nr = pages_nr;
> + pl->pages = pages;
> +
> + bio = bio_alloc(GFP_KERNEL, pages_nr);
> + 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++;
>> What if gen overflows? Maybe use dome idr for indexes? e.g. in
original patch there was ida_simple_get.
> It doesn't matter if it overflows. This index is only used for
generating string for VIRTIO_BLK_T_GET_ID requests and ensure it is the
same for consequential requests. This is serials that VM see.
> JFYI: will be later enhanced so userspace can load actual serial for
disk.
If we don't have this index at all and print "vhost-blk" for
VIRTIO_BLK_T_GET_ID, consequent requests would see the same string =)
So I believe there is some idea behind it to differentiate this index
between different vhost_blk_open-s but then what if index is reused
after it overflows and for two different vhost_blk_open-s we see the
same index? I still think there is a problem in current code which was
not there in Asias' version.
> +
> + 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
--
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.
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