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qemu-e2k/hw/block/virtio-blk.c
Denis Plotnikov c9b7d9ec21 virtio: increase virtqueue size for virtio-scsi and virtio-blk 
The goal is to reduce the amount of requests issued by a guest on
1M reads/writes. This rises the performance up to 4% on that kind of
disk access pattern.

The maximum chunk size to be used for the guest disk accessing is
limited with seg_max parameter, which represents the max amount of
pices in the scatter-geather list in one guest disk request.

Since seg_max is virqueue_size dependent, increasing the virtqueue
size increases seg_max, which, in turn, increases the maximum size
of data to be read/write from a guest disk.

More details in the original problem statment:
https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg03721.html

Suggested-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
Message-id: 20200214074648.958-1-dplotnikov@virtuozzo.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2020-02-22 08:26:47 +00:00

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/*
* Virtio Block Device
*
* Copyright IBM, Corp. 2007
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/iov.h"
#include "qemu/module.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
#include "trace.h"
#include "hw/block/block.h"
#include "hw/qdev-properties.h"
#include "sysemu/blockdev.h"
#include "sysemu/sysemu.h"
#include "sysemu/runstate.h"
#include "hw/virtio/virtio-blk.h"
#include "dataplane/virtio-blk.h"
#include "scsi/constants.h"
#ifdef __linux__
# include <scsi/sg.h>
#endif
#include "hw/virtio/virtio-bus.h"
#include "migration/qemu-file-types.h"
#include "hw/virtio/virtio-access.h"
/* Config size before the discard support (hide associated config fields) */
#define VIRTIO_BLK_CFG_SIZE offsetof(struct virtio_blk_config, \
max_discard_sectors)
/*
* Starting from the discard feature, we can use this array to properly
* set the config size depending on the features enabled.
*/
static VirtIOFeature feature_sizes[] = {
{.flags = 1ULL << VIRTIO_BLK_F_DISCARD,
.end = endof(struct virtio_blk_config, discard_sector_alignment)},
{.flags = 1ULL << VIRTIO_BLK_F_WRITE_ZEROES,
.end = endof(struct virtio_blk_config, write_zeroes_may_unmap)},
{}
};
static void virtio_blk_set_config_size(VirtIOBlock *s, uint64_t host_features)
{
s->config_size = MAX(VIRTIO_BLK_CFG_SIZE,
virtio_feature_get_config_size(feature_sizes, host_features));
assert(s->config_size <= sizeof(struct virtio_blk_config));
}
static void virtio_blk_init_request(VirtIOBlock *s, VirtQueue *vq,
VirtIOBlockReq *req)
{
req->dev = s;
req->vq = vq;
req->qiov.size = 0;
req->in_len = 0;
req->next = NULL;
req->mr_next = NULL;
}
static void virtio_blk_free_request(VirtIOBlockReq *req)
{
g_free(req);
}
static void virtio_blk_req_complete(VirtIOBlockReq *req, unsigned char status)
{
VirtIOBlock *s = req->dev;
VirtIODevice *vdev = VIRTIO_DEVICE(s);
trace_virtio_blk_req_complete(vdev, req, status);
stb_p(&req->in->status, status);
virtqueue_push(req->vq, &req->elem, req->in_len);
if (s->dataplane_started && !s->dataplane_disabled) {
virtio_blk_data_plane_notify(s->dataplane, req->vq);
} else {
virtio_notify(vdev, req->vq);
}
}
static int virtio_blk_handle_rw_error(VirtIOBlockReq *req, int error,
bool is_read, bool acct_failed)
{
VirtIOBlock *s = req->dev;
BlockErrorAction action = blk_get_error_action(s->blk, is_read, error);
if (action == BLOCK_ERROR_ACTION_STOP) {
/* Break the link as the next request is going to be parsed from the
* ring again. Otherwise we may end up doing a double completion! */
req->mr_next = NULL;
req->next = s->rq;
s->rq = req;
} else if (action == BLOCK_ERROR_ACTION_REPORT) {
virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
if (acct_failed) {
block_acct_failed(blk_get_stats(s->blk), &req->acct);
}
virtio_blk_free_request(req);
}
blk_error_action(s->blk, action, is_read, error);
return action != BLOCK_ERROR_ACTION_IGNORE;
}
static void virtio_blk_rw_complete(void *opaque, int ret)
{
VirtIOBlockReq *next = opaque;
VirtIOBlock *s = next->dev;
VirtIODevice *vdev = VIRTIO_DEVICE(s);
aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
while (next) {
VirtIOBlockReq *req = next;
next = req->mr_next;
trace_virtio_blk_rw_complete(vdev, req, ret);
if (req->qiov.nalloc != -1) {
/* If nalloc is != -1 req->qiov is a local copy of the original
* external iovec. It was allocated in submit_requests to be
* able to merge requests. */
qemu_iovec_destroy(&req->qiov);
}
if (ret) {
int p = virtio_ldl_p(VIRTIO_DEVICE(s), &req->out.type);
bool is_read = !(p & VIRTIO_BLK_T_OUT);
/* Note that memory may be dirtied on read failure. If the
* virtio request is not completed here, as is the case for
* BLOCK_ERROR_ACTION_STOP, the memory may not be copied
* correctly during live migration. While this is ugly,
* it is acceptable because the device is free to write to
* the memory until the request is completed (which will
* happen on the other side of the migration).
*/
if (virtio_blk_handle_rw_error(req, -ret, is_read, true)) {
continue;
}
}
virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
block_acct_done(blk_get_stats(s->blk), &req->acct);
virtio_blk_free_request(req);
}
aio_context_release(blk_get_aio_context(s->conf.conf.blk));
}
static void virtio_blk_flush_complete(void *opaque, int ret)
{
VirtIOBlockReq *req = opaque;
VirtIOBlock *s = req->dev;
aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
if (ret) {
if (virtio_blk_handle_rw_error(req, -ret, 0, true)) {
goto out;
}
}
virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
block_acct_done(blk_get_stats(s->blk), &req->acct);
virtio_blk_free_request(req);
out:
aio_context_release(blk_get_aio_context(s->conf.conf.blk));
}
static void virtio_blk_discard_write_zeroes_complete(void *opaque, int ret)
{
VirtIOBlockReq *req = opaque;
VirtIOBlock *s = req->dev;
bool is_write_zeroes = (virtio_ldl_p(VIRTIO_DEVICE(s), &req->out.type) &
~VIRTIO_BLK_T_BARRIER) == VIRTIO_BLK_T_WRITE_ZEROES;
aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
if (ret) {
if (virtio_blk_handle_rw_error(req, -ret, false, is_write_zeroes)) {
goto out;
}
}
virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
if (is_write_zeroes) {
block_acct_done(blk_get_stats(s->blk), &req->acct);
}
virtio_blk_free_request(req);
out:
aio_context_release(blk_get_aio_context(s->conf.conf.blk));
}
#ifdef __linux__
typedef struct {
VirtIOBlockReq *req;
struct sg_io_hdr hdr;
} VirtIOBlockIoctlReq;
static void virtio_blk_ioctl_complete(void *opaque, int status)
{
VirtIOBlockIoctlReq *ioctl_req = opaque;
VirtIOBlockReq *req = ioctl_req->req;
VirtIOBlock *s = req->dev;
VirtIODevice *vdev = VIRTIO_DEVICE(s);
struct virtio_scsi_inhdr *scsi;
struct sg_io_hdr *hdr;
scsi = (void *)req->elem.in_sg[req->elem.in_num - 2].iov_base;
if (status) {
status = VIRTIO_BLK_S_UNSUPP;
virtio_stl_p(vdev, &scsi->errors, 255);
goto out;
}
hdr = &ioctl_req->hdr;
/*
* From SCSI-Generic-HOWTO: "Some lower level drivers (e.g. ide-scsi)
* clear the masked_status field [hence status gets cleared too, see
* block/scsi_ioctl.c] even when a CHECK_CONDITION or COMMAND_TERMINATED
* status has occurred. However they do set DRIVER_SENSE in driver_status
* field. Also a (sb_len_wr > 0) indicates there is a sense buffer.
*/
if (hdr->status == 0 && hdr->sb_len_wr > 0) {
hdr->status = CHECK_CONDITION;
}
virtio_stl_p(vdev, &scsi->errors,
hdr->status | (hdr->msg_status << 8) |
(hdr->host_status << 16) | (hdr->driver_status << 24));
virtio_stl_p(vdev, &scsi->residual, hdr->resid);
virtio_stl_p(vdev, &scsi->sense_len, hdr->sb_len_wr);
virtio_stl_p(vdev, &scsi->data_len, hdr->dxfer_len);
out:
aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
virtio_blk_req_complete(req, status);
virtio_blk_free_request(req);
aio_context_release(blk_get_aio_context(s->conf.conf.blk));
g_free(ioctl_req);
}
#endif
static VirtIOBlockReq *virtio_blk_get_request(VirtIOBlock *s, VirtQueue *vq)
{
VirtIOBlockReq *req = virtqueue_pop(vq, sizeof(VirtIOBlockReq));
if (req) {
virtio_blk_init_request(s, vq, req);
}
return req;
}
static int virtio_blk_handle_scsi_req(VirtIOBlockReq *req)
{
int status = VIRTIO_BLK_S_OK;
struct virtio_scsi_inhdr *scsi = NULL;
VirtIOBlock *blk = req->dev;
VirtIODevice *vdev = VIRTIO_DEVICE(blk);
VirtQueueElement *elem = &req->elem;
#ifdef __linux__
int i;
VirtIOBlockIoctlReq *ioctl_req;
BlockAIOCB *acb;
#endif
/*
* We require at least one output segment each for the virtio_blk_outhdr
* and the SCSI command block.
*
* We also at least require the virtio_blk_inhdr, the virtio_scsi_inhdr
* and the sense buffer pointer in the input segments.
*/
if (elem->out_num < 2 || elem->in_num < 3) {
status = VIRTIO_BLK_S_IOERR;
goto fail;
}
/*
* The scsi inhdr is placed in the second-to-last input segment, just
* before the regular inhdr.
*/
scsi = (void *)elem->in_sg[elem->in_num - 2].iov_base;
if (!virtio_has_feature(blk->host_features, VIRTIO_BLK_F_SCSI)) {
status = VIRTIO_BLK_S_UNSUPP;
goto fail;
}
/*
* No support for bidirection commands yet.
*/
if (elem->out_num > 2 && elem->in_num > 3) {
status = VIRTIO_BLK_S_UNSUPP;
goto fail;
}
#ifdef __linux__
ioctl_req = g_new0(VirtIOBlockIoctlReq, 1);
ioctl_req->req = req;
ioctl_req->hdr.interface_id = 'S';
ioctl_req->hdr.cmd_len = elem->out_sg[1].iov_len;
ioctl_req->hdr.cmdp = elem->out_sg[1].iov_base;
ioctl_req->hdr.dxfer_len = 0;
if (elem->out_num > 2) {
/*
* If there are more than the minimally required 2 output segments
* there is write payload starting from the third iovec.
*/
ioctl_req->hdr.dxfer_direction = SG_DXFER_TO_DEV;
ioctl_req->hdr.iovec_count = elem->out_num - 2;
for (i = 0; i < ioctl_req->hdr.iovec_count; i++) {
ioctl_req->hdr.dxfer_len += elem->out_sg[i + 2].iov_len;
}
ioctl_req->hdr.dxferp = elem->out_sg + 2;
} else if (elem->in_num > 3) {
/*
* If we have more than 3 input segments the guest wants to actually
* read data.
*/
ioctl_req->hdr.dxfer_direction = SG_DXFER_FROM_DEV;
ioctl_req->hdr.iovec_count = elem->in_num - 3;
for (i = 0; i < ioctl_req->hdr.iovec_count; i++) {
ioctl_req->hdr.dxfer_len += elem->in_sg[i].iov_len;
}
ioctl_req->hdr.dxferp = elem->in_sg;
} else {
/*
* Some SCSI commands don't actually transfer any data.
*/
ioctl_req->hdr.dxfer_direction = SG_DXFER_NONE;
}
ioctl_req->hdr.sbp = elem->in_sg[elem->in_num - 3].iov_base;
ioctl_req->hdr.mx_sb_len = elem->in_sg[elem->in_num - 3].iov_len;
acb = blk_aio_ioctl(blk->blk, SG_IO, &ioctl_req->hdr,
virtio_blk_ioctl_complete, ioctl_req);
if (!acb) {
g_free(ioctl_req);
status = VIRTIO_BLK_S_UNSUPP;
goto fail;
}
return -EINPROGRESS;
#else
abort();
#endif
fail:
/* Just put anything nonzero so that the ioctl fails in the guest. */
if (scsi) {
virtio_stl_p(vdev, &scsi->errors, 255);
}
return status;
}
static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
{
int status;
status = virtio_blk_handle_scsi_req(req);
if (status != -EINPROGRESS) {
virtio_blk_req_complete(req, status);
virtio_blk_free_request(req);
}
}
static inline void submit_requests(BlockBackend *blk, MultiReqBuffer *mrb,
int start, int num_reqs, int niov)
{
QEMUIOVector *qiov = &mrb->reqs[start]->qiov;
int64_t sector_num = mrb->reqs[start]->sector_num;
bool is_write = mrb->is_write;
if (num_reqs > 1) {
int i;
struct iovec *tmp_iov = qiov->iov;
int tmp_niov = qiov->niov;
/* mrb->reqs[start]->qiov was initialized from external so we can't
* modify it here. We need to initialize it locally and then add the
* external iovecs. */
qemu_iovec_init(qiov, niov);
for (i = 0; i < tmp_niov; i++) {
qemu_iovec_add(qiov, tmp_iov[i].iov_base, tmp_iov[i].iov_len);
}
for (i = start + 1; i < start + num_reqs; i++) {
qemu_iovec_concat(qiov, &mrb->reqs[i]->qiov, 0,
mrb->reqs[i]->qiov.size);
mrb->reqs[i - 1]->mr_next = mrb->reqs[i];
}
trace_virtio_blk_submit_multireq(VIRTIO_DEVICE(mrb->reqs[start]->dev),
mrb, start, num_reqs,
sector_num << BDRV_SECTOR_BITS,
qiov->size, is_write);
block_acct_merge_done(blk_get_stats(blk),
is_write ? BLOCK_ACCT_WRITE : BLOCK_ACCT_READ,
num_reqs - 1);
}
if (is_write) {
blk_aio_pwritev(blk, sector_num << BDRV_SECTOR_BITS, qiov, 0,
virtio_blk_rw_complete, mrb->reqs[start]);
} else {
blk_aio_preadv(blk, sector_num << BDRV_SECTOR_BITS, qiov, 0,
virtio_blk_rw_complete, mrb->reqs[start]);
}
}
static int multireq_compare(const void *a, const void *b)
{
const VirtIOBlockReq *req1 = *(VirtIOBlockReq **)a,
*req2 = *(VirtIOBlockReq **)b;
/*
* Note that we can't simply subtract sector_num1 from sector_num2
* here as that could overflow the return value.
*/
if (req1->sector_num > req2->sector_num) {
return 1;
} else if (req1->sector_num < req2->sector_num) {
return -1;
} else {
return 0;
}
}
static void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb)
{
int i = 0, start = 0, num_reqs = 0, niov = 0, nb_sectors = 0;
uint32_t max_transfer;
int64_t sector_num = 0;
if (mrb->num_reqs == 1) {
submit_requests(blk, mrb, 0, 1, -1);
mrb->num_reqs = 0;
return;
}
max_transfer = blk_get_max_transfer(mrb->reqs[0]->dev->blk);
qsort(mrb->reqs, mrb->num_reqs, sizeof(*mrb->reqs),
&multireq_compare);
for (i = 0; i < mrb->num_reqs; i++) {
VirtIOBlockReq *req = mrb->reqs[i];
if (num_reqs > 0) {
/*
* NOTE: We cannot merge the requests in below situations:
* 1. requests are not sequential
* 2. merge would exceed maximum number of IOVs
* 3. merge would exceed maximum transfer length of backend device
*/
if (sector_num + nb_sectors != req->sector_num ||
niov > blk_get_max_iov(blk) - req->qiov.niov ||
req->qiov.size > max_transfer ||
nb_sectors > (max_transfer -
req->qiov.size) / BDRV_SECTOR_SIZE) {
submit_requests(blk, mrb, start, num_reqs, niov);
num_reqs = 0;
}
}
if (num_reqs == 0) {
sector_num = req->sector_num;
nb_sectors = niov = 0;
start = i;
}
nb_sectors += req->qiov.size / BDRV_SECTOR_SIZE;
niov += req->qiov.niov;
num_reqs++;
}
submit_requests(blk, mrb, start, num_reqs, niov);
mrb->num_reqs = 0;
}
static void virtio_blk_handle_flush(VirtIOBlockReq *req, MultiReqBuffer *mrb)
{
VirtIOBlock *s = req->dev;
block_acct_start(blk_get_stats(s->blk), &req->acct, 0,
BLOCK_ACCT_FLUSH);
/*
* Make sure all outstanding writes are posted to the backing device.
*/
if (mrb->is_write && mrb->num_reqs > 0) {
virtio_blk_submit_multireq(s->blk, mrb);
}
blk_aio_flush(s->blk, virtio_blk_flush_complete, req);
}
static bool virtio_blk_sect_range_ok(VirtIOBlock *dev,
uint64_t sector, size_t size)
{
uint64_t nb_sectors = size >> BDRV_SECTOR_BITS;
uint64_t total_sectors;
if (nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
return false;
}
if (sector & dev->sector_mask) {
return false;
}
if (size % dev->conf.conf.logical_block_size) {
return false;
}
blk_get_geometry(dev->blk, &total_sectors);
if (sector > total_sectors || nb_sectors > total_sectors - sector) {
return false;
}
return true;
}
static uint8_t virtio_blk_handle_discard_write_zeroes(VirtIOBlockReq *req,
struct virtio_blk_discard_write_zeroes *dwz_hdr, bool is_write_zeroes)
{
VirtIOBlock *s = req->dev;
VirtIODevice *vdev = VIRTIO_DEVICE(s);
uint64_t sector;
uint32_t num_sectors, flags, max_sectors;
uint8_t err_status;
int bytes;
sector = virtio_ldq_p(vdev, &dwz_hdr->sector);
num_sectors = virtio_ldl_p(vdev, &dwz_hdr->num_sectors);
flags = virtio_ldl_p(vdev, &dwz_hdr->flags);
max_sectors = is_write_zeroes ? s->conf.max_write_zeroes_sectors :
s->conf.max_discard_sectors;
/*
* max_sectors is at most BDRV_REQUEST_MAX_SECTORS, this check
* make us sure that "num_sectors << BDRV_SECTOR_BITS" can fit in
* the integer variable.
*/
if (unlikely(num_sectors > max_sectors)) {
err_status = VIRTIO_BLK_S_IOERR;
goto err;
}
bytes = num_sectors << BDRV_SECTOR_BITS;
if (unlikely(!virtio_blk_sect_range_ok(s, sector, bytes))) {
err_status = VIRTIO_BLK_S_IOERR;
goto err;
}
/*
* The device MUST set the status byte to VIRTIO_BLK_S_UNSUPP for discard
* and write zeroes commands if any unknown flag is set.
*/
if (unlikely(flags & ~VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP)) {
err_status = VIRTIO_BLK_S_UNSUPP;
goto err;
}
if (is_write_zeroes) { /* VIRTIO_BLK_T_WRITE_ZEROES */
int blk_aio_flags = 0;
if (flags & VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP) {
blk_aio_flags |= BDRV_REQ_MAY_UNMAP;
}
block_acct_start(blk_get_stats(s->blk), &req->acct, bytes,
BLOCK_ACCT_WRITE);
blk_aio_pwrite_zeroes(s->blk, sector << BDRV_SECTOR_BITS,
bytes, blk_aio_flags,
virtio_blk_discard_write_zeroes_complete, req);
} else { /* VIRTIO_BLK_T_DISCARD */
/*
* The device MUST set the status byte to VIRTIO_BLK_S_UNSUPP for
* discard commands if the unmap flag is set.
*/
if (unlikely(flags & VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP)) {
err_status = VIRTIO_BLK_S_UNSUPP;
goto err;
}
blk_aio_pdiscard(s->blk, sector << BDRV_SECTOR_BITS, bytes,
virtio_blk_discard_write_zeroes_complete, req);
}
return VIRTIO_BLK_S_OK;
err:
if (is_write_zeroes) {
block_acct_invalid(blk_get_stats(s->blk), BLOCK_ACCT_WRITE);
}
return err_status;
}
static int virtio_blk_handle_request(VirtIOBlockReq *req, MultiReqBuffer *mrb)
{
uint32_t type;
struct iovec *in_iov = req->elem.in_sg;
struct iovec *out_iov = req->elem.out_sg;
unsigned in_num = req->elem.in_num;
unsigned out_num = req->elem.out_num;
VirtIOBlock *s = req->dev;
VirtIODevice *vdev = VIRTIO_DEVICE(s);
if (req->elem.out_num < 1 || req->elem.in_num < 1) {
virtio_error(vdev, "virtio-blk missing headers");
return -1;
}
if (unlikely(iov_to_buf(out_iov, out_num, 0, &req->out,
sizeof(req->out)) != sizeof(req->out))) {
virtio_error(vdev, "virtio-blk request outhdr too short");
return -1;
}
iov_discard_front(&out_iov, &out_num, sizeof(req->out));
if (in_iov[in_num - 1].iov_len < sizeof(struct virtio_blk_inhdr)) {
virtio_error(vdev, "virtio-blk request inhdr too short");
return -1;
}
/* We always touch the last byte, so just see how big in_iov is. */
req->in_len = iov_size(in_iov, in_num);
req->in = (void *)in_iov[in_num - 1].iov_base
+ in_iov[in_num - 1].iov_len
- sizeof(struct virtio_blk_inhdr);
iov_discard_back(in_iov, &in_num, sizeof(struct virtio_blk_inhdr));
type = virtio_ldl_p(vdev, &req->out.type);
/* VIRTIO_BLK_T_OUT defines the command direction. VIRTIO_BLK_T_BARRIER
* is an optional flag. Although a guest should not send this flag if
* not negotiated we ignored it in the past. So keep ignoring it. */
switch (type & ~(VIRTIO_BLK_T_OUT | VIRTIO_BLK_T_BARRIER)) {
case VIRTIO_BLK_T_IN:
{
bool is_write = type & VIRTIO_BLK_T_OUT;
req->sector_num = virtio_ldq_p(vdev, &req->out.sector);
if (is_write) {
qemu_iovec_init_external(&req->qiov, out_iov, out_num);
trace_virtio_blk_handle_write(vdev, req, req->sector_num,
req->qiov.size / BDRV_SECTOR_SIZE);
} else {
qemu_iovec_init_external(&req->qiov, in_iov, in_num);
trace_virtio_blk_handle_read(vdev, req, req->sector_num,
req->qiov.size / BDRV_SECTOR_SIZE);
}
if (!virtio_blk_sect_range_ok(s, req->sector_num, req->qiov.size)) {
virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
block_acct_invalid(blk_get_stats(s->blk),
is_write ? BLOCK_ACCT_WRITE : BLOCK_ACCT_READ);
virtio_blk_free_request(req);
return 0;
}
block_acct_start(blk_get_stats(s->blk), &req->acct, req->qiov.size,
is_write ? BLOCK_ACCT_WRITE : BLOCK_ACCT_READ);
/* merge would exceed maximum number of requests or IO direction
* changes */
if (mrb->num_reqs > 0 && (mrb->num_reqs == VIRTIO_BLK_MAX_MERGE_REQS ||
is_write != mrb->is_write ||
!s->conf.request_merging)) {
virtio_blk_submit_multireq(s->blk, mrb);
}
assert(mrb->num_reqs < VIRTIO_BLK_MAX_MERGE_REQS);
mrb->reqs[mrb->num_reqs++] = req;
mrb->is_write = is_write;
break;
}
case VIRTIO_BLK_T_FLUSH:
virtio_blk_handle_flush(req, mrb);
break;
case VIRTIO_BLK_T_SCSI_CMD:
virtio_blk_handle_scsi(req);
break;
case VIRTIO_BLK_T_GET_ID:
{
/*
* NB: per existing s/n string convention the string is
* terminated by '\0' only when shorter than buffer.
*/
const char *serial = s->conf.serial ? s->conf.serial : "";
size_t size = MIN(strlen(serial) + 1,
MIN(iov_size(in_iov, in_num),
VIRTIO_BLK_ID_BYTES));
iov_from_buf(in_iov, in_num, 0, serial, size);
virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
virtio_blk_free_request(req);
break;
}
/*
* VIRTIO_BLK_T_DISCARD and VIRTIO_BLK_T_WRITE_ZEROES are defined with
* VIRTIO_BLK_T_OUT flag set. We masked this flag in the switch statement,
* so we must mask it for these requests, then we will check if it is set.
*/
case VIRTIO_BLK_T_DISCARD & ~VIRTIO_BLK_T_OUT:
case VIRTIO_BLK_T_WRITE_ZEROES & ~VIRTIO_BLK_T_OUT:
{
struct virtio_blk_discard_write_zeroes dwz_hdr;
size_t out_len = iov_size(out_iov, out_num);
bool is_write_zeroes = (type & ~VIRTIO_BLK_T_BARRIER) ==
VIRTIO_BLK_T_WRITE_ZEROES;
uint8_t err_status;
/*
* Unsupported if VIRTIO_BLK_T_OUT is not set or the request contains
* more than one segment.
*/
if (unlikely(!(type & VIRTIO_BLK_T_OUT) ||
out_len > sizeof(dwz_hdr))) {
virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);
virtio_blk_free_request(req);
return 0;
}
if (unlikely(iov_to_buf(out_iov, out_num, 0, &dwz_hdr,
sizeof(dwz_hdr)) != sizeof(dwz_hdr))) {
virtio_error(vdev, "virtio-blk discard/write_zeroes header"
" too short");
return -1;
}
err_status = virtio_blk_handle_discard_write_zeroes(req, &dwz_hdr,
is_write_zeroes);
if (err_status != VIRTIO_BLK_S_OK) {
virtio_blk_req_complete(req, err_status);
virtio_blk_free_request(req);
}
break;
}
default:
virtio_blk_req_complete(req, VIRTIO_BLK_S_UNSUPP);
virtio_blk_free_request(req);
}
return 0;
}
bool virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
{
VirtIOBlockReq *req;
MultiReqBuffer mrb = {};
bool suppress_notifications = virtio_queue_get_notification(vq);
bool progress = false;
aio_context_acquire(blk_get_aio_context(s->blk));
blk_io_plug(s->blk);
do {
if (suppress_notifications) {
virtio_queue_set_notification(vq, 0);
}
while ((req = virtio_blk_get_request(s, vq))) {
progress = true;
if (virtio_blk_handle_request(req, &mrb)) {
virtqueue_detach_element(req->vq, &req->elem, 0);
virtio_blk_free_request(req);
break;
}
}
if (suppress_notifications) {
virtio_queue_set_notification(vq, 1);
}
} while (!virtio_queue_empty(vq));
if (mrb.num_reqs) {
virtio_blk_submit_multireq(s->blk, &mrb);
}
blk_io_unplug(s->blk);
aio_context_release(blk_get_aio_context(s->blk));
return progress;
}
static void virtio_blk_handle_output_do(VirtIOBlock *s, VirtQueue *vq)
{
virtio_blk_handle_vq(s, vq);
}
static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
{
VirtIOBlock *s = (VirtIOBlock *)vdev;
if (s->dataplane) {
/* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
* dataplane here instead of waiting for .set_status().
*/
virtio_device_start_ioeventfd(vdev);
if (!s->dataplane_disabled) {
return;
}
}
virtio_blk_handle_output_do(s, vq);
}
static void virtio_blk_dma_restart_bh(void *opaque)
{
VirtIOBlock *s = opaque;
VirtIOBlockReq *req = s->rq;
MultiReqBuffer mrb = {};
qemu_bh_delete(s->bh);
s->bh = NULL;
s->rq = NULL;
aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
while (req) {
VirtIOBlockReq *next = req->next;
if (virtio_blk_handle_request(req, &mrb)) {
/* Device is now broken and won't do any processing until it gets
* reset. Already queued requests will be lost: let's purge them.
*/
while (req) {
next = req->next;
virtqueue_detach_element(req->vq, &req->elem, 0);
virtio_blk_free_request(req);
req = next;
}
break;
}
req = next;
}
if (mrb.num_reqs) {
virtio_blk_submit_multireq(s->blk, &mrb);
}
blk_dec_in_flight(s->conf.conf.blk);
aio_context_release(blk_get_aio_context(s->conf.conf.blk));
}
static void virtio_blk_dma_restart_cb(void *opaque, int running,
RunState state)
{
VirtIOBlock *s = opaque;
if (!running) {
return;
}
if (!s->bh) {
/* FIXME The data plane is not started yet, so these requests are
* processed in the main thread. */
s->bh = aio_bh_new(blk_get_aio_context(s->conf.conf.blk),
virtio_blk_dma_restart_bh, s);
blk_inc_in_flight(s->conf.conf.blk);
qemu_bh_schedule(s->bh);
}
}
static void virtio_blk_reset(VirtIODevice *vdev)
{
VirtIOBlock *s = VIRTIO_BLK(vdev);
AioContext *ctx;
VirtIOBlockReq *req;
ctx = blk_get_aio_context(s->blk);
aio_context_acquire(ctx);
blk_drain(s->blk);
/* We drop queued requests after blk_drain() because blk_drain() itself can
* produce them. */
while (s->rq) {
req = s->rq;
s->rq = req->next;
virtqueue_detach_element(req->vq, &req->elem, 0);
virtio_blk_free_request(req);
}
aio_context_release(ctx);
assert(!s->dataplane_started);
blk_set_enable_write_cache(s->blk, s->original_wce);
}
/* coalesce internal state, copy to pci i/o region 0
*/
static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
{
VirtIOBlock *s = VIRTIO_BLK(vdev);
BlockConf *conf = &s->conf.conf;
struct virtio_blk_config blkcfg;
uint64_t capacity;
int64_t length;
int blk_size = conf->logical_block_size;
blk_get_geometry(s->blk, &capacity);
memset(&blkcfg, 0, sizeof(blkcfg));
virtio_stq_p(vdev, &blkcfg.capacity, capacity);
virtio_stl_p(vdev, &blkcfg.seg_max,
s->conf.seg_max_adjust ? s->conf.queue_size - 2 : 128 - 2);
virtio_stw_p(vdev, &blkcfg.geometry.cylinders, conf->cyls);
virtio_stl_p(vdev, &blkcfg.blk_size, blk_size);
virtio_stw_p(vdev, &blkcfg.min_io_size, conf->min_io_size / blk_size);
virtio_stw_p(vdev, &blkcfg.opt_io_size, conf->opt_io_size / blk_size);
blkcfg.geometry.heads = conf->heads;
/*
* We must ensure that the block device capacity is a multiple of
* the logical block size. If that is not the case, let's use
* sector_mask to adopt the geometry to have a correct picture.
* For those devices where the capacity is ok for the given geometry
* we don't touch the sector value of the geometry, since some devices
* (like s390 dasd) need a specific value. Here the capacity is already
* cyls*heads*secs*blk_size and the sector value is not block size
* divided by 512 - instead it is the amount of blk_size blocks
* per track (cylinder).
*/
length = blk_getlength(s->blk);
if (length > 0 && length / conf->heads / conf->secs % blk_size) {
blkcfg.geometry.sectors = conf->secs & ~s->sector_mask;
} else {
blkcfg.geometry.sectors = conf->secs;
}
blkcfg.size_max = 0;
blkcfg.physical_block_exp = get_physical_block_exp(conf);
blkcfg.alignment_offset = 0;
blkcfg.wce = blk_enable_write_cache(s->blk);
virtio_stw_p(vdev, &blkcfg.num_queues, s->conf.num_queues);
if (virtio_has_feature(s->host_features, VIRTIO_BLK_F_DISCARD)) {
virtio_stl_p(vdev, &blkcfg.max_discard_sectors,
s->conf.max_discard_sectors);
virtio_stl_p(vdev, &blkcfg.discard_sector_alignment,
blk_size >> BDRV_SECTOR_BITS);
/*
* We support only one segment per request since multiple segments
* are not widely used and there are no userspace APIs that allow
* applications to submit multiple segments in a single call.
*/
virtio_stl_p(vdev, &blkcfg.max_discard_seg, 1);
}
if (virtio_has_feature(s->host_features, VIRTIO_BLK_F_WRITE_ZEROES)) {
virtio_stl_p(vdev, &blkcfg.max_write_zeroes_sectors,
s->conf.max_write_zeroes_sectors);
blkcfg.write_zeroes_may_unmap = 1;
virtio_stl_p(vdev, &blkcfg.max_write_zeroes_seg, 1);
}
memcpy(config, &blkcfg, s->config_size);
}
static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config)
{
VirtIOBlock *s = VIRTIO_BLK(vdev);
struct virtio_blk_config blkcfg;
memcpy(&blkcfg, config, s->config_size);
aio_context_acquire(blk_get_aio_context(s->blk));
blk_set_enable_write_cache(s->blk, blkcfg.wce != 0);
aio_context_release(blk_get_aio_context(s->blk));
}
static uint64_t virtio_blk_get_features(VirtIODevice *vdev, uint64_t features,
Error **errp)
{
VirtIOBlock *s = VIRTIO_BLK(vdev);
/* Firstly sync all virtio-blk possible supported features */
features |= s->host_features;
virtio_add_feature(&features, VIRTIO_BLK_F_SEG_MAX);
virtio_add_feature(&features, VIRTIO_BLK_F_GEOMETRY);
virtio_add_feature(&features, VIRTIO_BLK_F_TOPOLOGY);
virtio_add_feature(&features, VIRTIO_BLK_F_BLK_SIZE);
if (virtio_has_feature(features, VIRTIO_F_VERSION_1)) {
if (virtio_has_feature(s->host_features, VIRTIO_BLK_F_SCSI)) {
error_setg(errp, "Please set scsi=off for virtio-blk devices in order to use virtio 1.0");
return 0;
}
} else {
virtio_clear_feature(&features, VIRTIO_F_ANY_LAYOUT);
virtio_add_feature(&features, VIRTIO_BLK_F_SCSI);
}
if (blk_enable_write_cache(s->blk) ||
(s->conf.x_enable_wce_if_config_wce &&
virtio_has_feature(features, VIRTIO_BLK_F_CONFIG_WCE))) {
virtio_add_feature(&features, VIRTIO_BLK_F_WCE);
}
if (blk_is_read_only(s->blk)) {
virtio_add_feature(&features, VIRTIO_BLK_F_RO);
}
if (s->conf.num_queues > 1) {
virtio_add_feature(&features, VIRTIO_BLK_F_MQ);
}
return features;
}
static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
{
VirtIOBlock *s = VIRTIO_BLK(vdev);
if (!(status & (VIRTIO_CONFIG_S_DRIVER | VIRTIO_CONFIG_S_DRIVER_OK))) {
assert(!s->dataplane_started);
}
if (!(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
return;
}
/* A guest that supports VIRTIO_BLK_F_CONFIG_WCE must be able to send
* cache flushes. Thus, the "auto writethrough" behavior is never
* necessary for guests that support the VIRTIO_BLK_F_CONFIG_WCE feature.
* Leaving it enabled would break the following sequence:
*
* Guest started with "-drive cache=writethrough"
* Guest sets status to 0
* Guest sets DRIVER bit in status field
* Guest reads host features (WCE=0, CONFIG_WCE=1)
* Guest writes guest features (WCE=0, CONFIG_WCE=1)
* Guest writes 1 to the WCE configuration field (writeback mode)
* Guest sets DRIVER_OK bit in status field
*
* s->blk would erroneously be placed in writethrough mode.
*/
if (!virtio_vdev_has_feature(vdev, VIRTIO_BLK_F_CONFIG_WCE)) {
aio_context_acquire(blk_get_aio_context(s->blk));
blk_set_enable_write_cache(s->blk,
virtio_vdev_has_feature(vdev,
VIRTIO_BLK_F_WCE));
aio_context_release(blk_get_aio_context(s->blk));
}
}
static void virtio_blk_save_device(VirtIODevice *vdev, QEMUFile *f)
{
VirtIOBlock *s = VIRTIO_BLK(vdev);
VirtIOBlockReq *req = s->rq;
while (req) {
qemu_put_sbyte(f, 1);
if (s->conf.num_queues > 1) {
qemu_put_be32(f, virtio_get_queue_index(req->vq));
}
qemu_put_virtqueue_element(vdev, f, &req->elem);
req = req->next;
}
qemu_put_sbyte(f, 0);
}
static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f,
int version_id)
{
VirtIOBlock *s = VIRTIO_BLK(vdev);
while (qemu_get_sbyte(f)) {
unsigned nvqs = s->conf.num_queues;
unsigned vq_idx = 0;
VirtIOBlockReq *req;
if (nvqs > 1) {
vq_idx = qemu_get_be32(f);
if (vq_idx >= nvqs) {
error_report("Invalid virtqueue index in request list: %#x",
vq_idx);
return -EINVAL;
}
}
req = qemu_get_virtqueue_element(vdev, f, sizeof(VirtIOBlockReq));
virtio_blk_init_request(s, virtio_get_queue(vdev, vq_idx), req);
req->next = s->rq;
s->rq = req;
}
return 0;
}
static void virtio_resize_cb(void *opaque)
{
VirtIODevice *vdev = opaque;
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
virtio_notify_config(vdev);
}
static void virtio_blk_resize(void *opaque)
{
VirtIODevice *vdev = VIRTIO_DEVICE(opaque);
/*
* virtio_notify_config() needs to acquire the global mutex,
* so it can't be called from an iothread. Instead, schedule
* it to be run in the main context BH.
*/
aio_bh_schedule_oneshot(qemu_get_aio_context(), virtio_resize_cb, vdev);
}
static const BlockDevOps virtio_block_ops = {
.resize_cb = virtio_blk_resize,
};
static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
{
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VirtIOBlock *s = VIRTIO_BLK(dev);
VirtIOBlkConf *conf = &s->conf;
Error *err = NULL;
unsigned i;
if (!conf->conf.blk) {
error_setg(errp, "drive property not set");
return;
}
if (!blk_is_inserted(conf->conf.blk)) {
error_setg(errp, "Device needs media, but drive is empty");
return;
}
if (!conf->num_queues) {
error_setg(errp, "num-queues property must be larger than 0");
return;
}
if (conf->queue_size <= 2) {
error_setg(errp, "invalid queue-size property (%" PRIu16 "), "
"must be > 2", conf->queue_size);
return;
}
if (!is_power_of_2(conf->queue_size) ||
conf->queue_size > VIRTQUEUE_MAX_SIZE) {
error_setg(errp, "invalid queue-size property (%" PRIu16 "), "
"must be a power of 2 (max %d)",
conf->queue_size, VIRTQUEUE_MAX_SIZE);
return;
}
if (!blkconf_apply_backend_options(&conf->conf,
blk_is_read_only(conf->conf.blk), true,
errp)) {
return;
}
s->original_wce = blk_enable_write_cache(conf->conf.blk);
if (!blkconf_geometry(&conf->conf, NULL, 65535, 255, 255, errp)) {
return;
}
blkconf_blocksizes(&conf->conf);
if (conf->conf.logical_block_size >
conf->conf.physical_block_size) {
error_setg(errp,
"logical_block_size > physical_block_size not supported");
return;
}
if (virtio_has_feature(s->host_features, VIRTIO_BLK_F_DISCARD) &&
(!conf->max_discard_sectors ||
conf->max_discard_sectors > BDRV_REQUEST_MAX_SECTORS)) {
error_setg(errp, "invalid max-discard-sectors property (%" PRIu32 ")"
", must be between 1 and %d",
conf->max_discard_sectors, (int)BDRV_REQUEST_MAX_SECTORS);
return;
}
if (virtio_has_feature(s->host_features, VIRTIO_BLK_F_WRITE_ZEROES) &&
(!conf->max_write_zeroes_sectors ||
conf->max_write_zeroes_sectors > BDRV_REQUEST_MAX_SECTORS)) {
error_setg(errp, "invalid max-write-zeroes-sectors property (%" PRIu32
"), must be between 1 and %d",
conf->max_write_zeroes_sectors,
(int)BDRV_REQUEST_MAX_SECTORS);
return;
}
virtio_blk_set_config_size(s, s->host_features);
virtio_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK, s->config_size);
s->blk = conf->conf.blk;
s->rq = NULL;
s->sector_mask = (s->conf.conf.logical_block_size / BDRV_SECTOR_SIZE) - 1;
for (i = 0; i < conf->num_queues; i++) {
virtio_add_queue(vdev, conf->queue_size, virtio_blk_handle_output);
}
virtio_blk_data_plane_create(vdev, conf, &s->dataplane, &err);
if (err != NULL) {
error_propagate(errp, err);
virtio_cleanup(vdev);
return;
}
s->change = qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
blk_set_dev_ops(s->blk, &virtio_block_ops, s);
blk_set_guest_block_size(s->blk, s->conf.conf.logical_block_size);
blk_iostatus_enable(s->blk);
add_boot_device_lchs(dev, "/disk@0,0",
conf->conf.lcyls,
conf->conf.lheads,
conf->conf.lsecs);
}
static void virtio_blk_device_unrealize(DeviceState *dev, Error **errp)
{
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VirtIOBlock *s = VIRTIO_BLK(dev);
VirtIOBlkConf *conf = &s->conf;
unsigned i;
blk_drain(s->blk);
del_boot_device_lchs(dev, "/disk@0,0");
virtio_blk_data_plane_destroy(s->dataplane);
s->dataplane = NULL;
for (i = 0; i < conf->num_queues; i++) {
virtio_del_queue(vdev, i);
}
qemu_del_vm_change_state_handler(s->change);
blockdev_mark_auto_del(s->blk);
virtio_cleanup(vdev);
}
static void virtio_blk_instance_init(Object *obj)
{
VirtIOBlock *s = VIRTIO_BLK(obj);
device_add_bootindex_property(obj, &s->conf.conf.bootindex,
"bootindex", "/disk@0,0",
DEVICE(obj), NULL);
}
static const VMStateDescription vmstate_virtio_blk = {
.name = "virtio-blk",
.minimum_version_id = 2,
.version_id = 2,
.fields = (VMStateField[]) {
VMSTATE_VIRTIO_DEVICE,
VMSTATE_END_OF_LIST()
},
};
static Property virtio_blk_properties[] = {
DEFINE_BLOCK_PROPERTIES(VirtIOBlock, conf.conf),
DEFINE_BLOCK_ERROR_PROPERTIES(VirtIOBlock, conf.conf),
DEFINE_BLOCK_CHS_PROPERTIES(VirtIOBlock, conf.conf),
DEFINE_PROP_STRING("serial", VirtIOBlock, conf.serial),
DEFINE_PROP_BIT64("config-wce", VirtIOBlock, host_features,
VIRTIO_BLK_F_CONFIG_WCE, true),
#ifdef __linux__
DEFINE_PROP_BIT64("scsi", VirtIOBlock, host_features,
VIRTIO_BLK_F_SCSI, false),
#endif
DEFINE_PROP_BIT("request-merging", VirtIOBlock, conf.request_merging, 0,
true),
DEFINE_PROP_UINT16("num-queues", VirtIOBlock, conf.num_queues, 1),
DEFINE_PROP_UINT16("queue-size", VirtIOBlock, conf.queue_size, 256),
DEFINE_PROP_BOOL("seg-max-adjust", VirtIOBlock, conf.seg_max_adjust, true),
DEFINE_PROP_LINK("iothread", VirtIOBlock, conf.iothread, TYPE_IOTHREAD,
IOThread *),
DEFINE_PROP_BIT64("discard", VirtIOBlock, host_features,
VIRTIO_BLK_F_DISCARD, true),
DEFINE_PROP_BIT64("write-zeroes", VirtIOBlock, host_features,
VIRTIO_BLK_F_WRITE_ZEROES, true),
DEFINE_PROP_UINT32("max-discard-sectors", VirtIOBlock,
conf.max_discard_sectors, BDRV_REQUEST_MAX_SECTORS),
DEFINE_PROP_UINT32("max-write-zeroes-sectors", VirtIOBlock,
conf.max_write_zeroes_sectors, BDRV_REQUEST_MAX_SECTORS),
DEFINE_PROP_BOOL("x-enable-wce-if-config-wce", VirtIOBlock,
conf.x_enable_wce_if_config_wce, true),
DEFINE_PROP_END_OF_LIST(),
};
static void virtio_blk_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
device_class_set_props(dc, virtio_blk_properties);
dc->vmsd = &vmstate_virtio_blk;
set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
vdc->realize = virtio_blk_device_realize;
vdc->unrealize = virtio_blk_device_unrealize;
vdc->get_config = virtio_blk_update_config;
vdc->set_config = virtio_blk_set_config;
vdc->get_features = virtio_blk_get_features;
vdc->set_status = virtio_blk_set_status;
vdc->reset = virtio_blk_reset;
vdc->save = virtio_blk_save_device;
vdc->load = virtio_blk_load_device;
vdc->start_ioeventfd = virtio_blk_data_plane_start;
vdc->stop_ioeventfd = virtio_blk_data_plane_stop;
}
static const TypeInfo virtio_blk_info = {
.name = TYPE_VIRTIO_BLK,
.parent = TYPE_VIRTIO_DEVICE,
.instance_size = sizeof(VirtIOBlock),
.instance_init = virtio_blk_instance_init,
.class_init = virtio_blk_class_init,
};
static void virtio_register_types(void)
{
type_register_static(&virtio_blk_info);
}
type_init(virtio_register_types)
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