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qemu-e2k/hw/block/dataplane/xen-block.c

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/*
* Copyright (c) 2018 Citrix Systems Inc.
* (c) Gerd Hoffmann <kraxel@redhat.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; under version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, see <http://www.gnu.org/licenses/>.
*
* Contributions after 2012-01-13 are licensed under the terms of the
* GNU GPL, version 2 or (at your option) any later version.
*/
#include "qemu/osdep.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
#include "qemu/memalign.h"
#include "qapi/error.h"
#include "hw/xen/xen_common.h"
#include "hw/block/xen_blkif.h"
#include "sysemu/block-backend.h"
#include "sysemu/iothread.h"
#include "xen-block.h"
typedef struct XenBlockRequest {
blkif_request_t req;
int16_t status;
off_t start;
QEMUIOVector v;
void *buf;
size_t size;
int presync;
int aio_inflight;
int aio_errors;
XenBlockDataPlane *dataplane;
QLIST_ENTRY(XenBlockRequest) list;
BlockAcctCookie acct;
} XenBlockRequest;
struct XenBlockDataPlane {
XenDevice *xendev;
XenEventChannel *event_channel;
unsigned int *ring_ref;
unsigned int nr_ring_ref;
void *sring;
int protocol;
blkif_back_rings_t rings;
int more_work;
QLIST_HEAD(inflight_head, XenBlockRequest) inflight;
QLIST_HEAD(freelist_head, XenBlockRequest) freelist;
int requests_total;
int requests_inflight;
unsigned int max_requests;
BlockBackend *blk;
unsigned int sector_size;
QEMUBH *bh;
IOThread *iothread;
AioContext *ctx;
};
static int xen_block_send_response(XenBlockRequest *request);
static void reset_request(XenBlockRequest *request)
{
memset(&request->req, 0, sizeof(request->req));
request->status = 0;
request->start = 0;
request->size = 0;
request->presync = 0;
request->aio_inflight = 0;
request->aio_errors = 0;
request->dataplane = NULL;
memset(&request->list, 0, sizeof(request->list));
memset(&request->acct, 0, sizeof(request->acct));
qemu_iovec_reset(&request->v);
}
static XenBlockRequest *xen_block_start_request(XenBlockDataPlane *dataplane)
{
XenBlockRequest *request = NULL;
if (QLIST_EMPTY(&dataplane->freelist)) {
if (dataplane->requests_total >= dataplane->max_requests) {
goto out;
}
/* allocate new struct */
request = g_malloc0(sizeof(*request));
request->dataplane = dataplane;
/*
* We cannot need more pages per requests than this, and since we
* re-use requests, allocate the memory once here. It will be freed
* xen_block_dataplane_destroy() when the request list is freed.
*/
request->buf = qemu_memalign(XC_PAGE_SIZE,
BLKIF_MAX_SEGMENTS_PER_REQUEST *
XC_PAGE_SIZE);
dataplane->requests_total++;
qemu_iovec_init(&request->v, 1);
} else {
/* get one from freelist */
request = QLIST_FIRST(&dataplane->freelist);
QLIST_REMOVE(request, list);
}
QLIST_INSERT_HEAD(&dataplane->inflight, request, list);
dataplane->requests_inflight++;
out:
return request;
}
static void xen_block_complete_request(XenBlockRequest *request)
{
XenBlockDataPlane *dataplane = request->dataplane;
if (xen_block_send_response(request)) {
Error *local_err = NULL;
xen_device_notify_event_channel(dataplane->xendev,
dataplane->event_channel,
&local_err);
if (local_err) {
error_report_err(local_err);
}
}
QLIST_REMOVE(request, list);
dataplane->requests_inflight--;
reset_request(request);
request->dataplane = dataplane;
QLIST_INSERT_HEAD(&dataplane->freelist, request, list);
}
/*
* translate request into iovec + start offset
* do sanity checks along the way
*/
static int xen_block_parse_request(XenBlockRequest *request)
{
XenBlockDataPlane *dataplane = request->dataplane;
size_t len;
int i;
switch (request->req.operation) {
case BLKIF_OP_READ:
break;
case BLKIF_OP_FLUSH_DISKCACHE:
request->presync = 1;
if (!request->req.nr_segments) {
return 0;
}
/* fall through */
case BLKIF_OP_WRITE:
break;
case BLKIF_OP_DISCARD:
return 0;
default:
error_report("error: unknown operation (%d)", request->req.operation);
goto err;
};
if (request->req.operation != BLKIF_OP_READ &&
!blk_is_writable(dataplane->blk)) {
error_report("error: write req for ro device");
goto err;
}
request->start = request->req.sector_number * dataplane->sector_size;
for (i = 0; i < request->req.nr_segments; i++) {
if (i == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
error_report("error: nr_segments too big");
goto err;
}
if (request->req.seg[i].first_sect > request->req.seg[i].last_sect) {
error_report("error: first > last sector");
goto err;
}
if (request->req.seg[i].last_sect * dataplane->sector_size >=
XC_PAGE_SIZE) {
error_report("error: page crossing");
goto err;
}
len = (request->req.seg[i].last_sect -
request->req.seg[i].first_sect + 1) * dataplane->sector_size;
request->size += len;
}
if (request->start + request->size > blk_getlength(dataplane->blk)) {
error_report("error: access beyond end of file");
goto err;
}
return 0;
err:
request->status = BLKIF_RSP_ERROR;
return -1;
}
static int xen_block_copy_request(XenBlockRequest *request)
{
XenBlockDataPlane *dataplane = request->dataplane;
XenDevice *xendev = dataplane->xendev;
XenDeviceGrantCopySegment segs[BLKIF_MAX_SEGMENTS_PER_REQUEST];
int i, count;
bool to_domain = (request->req.operation == BLKIF_OP_READ);
void *virt = request->buf;
Error *local_err = NULL;
if (request->req.nr_segments == 0) {
return 0;
}
count = request->req.nr_segments;
for (i = 0; i < count; i++) {
if (to_domain) {
segs[i].dest.foreign.ref = request->req.seg[i].gref;
segs[i].dest.foreign.offset = request->req.seg[i].first_sect *
dataplane->sector_size;
segs[i].source.virt = virt;
} else {
segs[i].source.foreign.ref = request->req.seg[i].gref;
segs[i].source.foreign.offset = request->req.seg[i].first_sect *
dataplane->sector_size;
segs[i].dest.virt = virt;
}
segs[i].len = (request->req.seg[i].last_sect -
request->req.seg[i].first_sect + 1) *
dataplane->sector_size;
virt += segs[i].len;
}
xen_device_copy_grant_refs(xendev, to_domain, segs, count, &local_err);
if (local_err) {
error_reportf_err(local_err, "failed to copy data: ");
request->aio_errors++;
return -1;
}
return 0;
}
static int xen_block_do_aio(XenBlockRequest *request);
static void xen_block_complete_aio(void *opaque, int ret)
{
XenBlockRequest *request = opaque;
XenBlockDataPlane *dataplane = request->dataplane;
aio_context_acquire(dataplane->ctx);
if (ret != 0) {
error_report("%s I/O error",
request->req.operation == BLKIF_OP_READ ?
"read" : "write");
request->aio_errors++;
}
request->aio_inflight--;
if (request->presync) {
request->presync = 0;
xen_block_do_aio(request);
goto done;
}
if (request->aio_inflight > 0) {
goto done;
}
switch (request->req.operation) {
case BLKIF_OP_READ:
/* in case of failure request->aio_errors is increased */
if (ret == 0) {
xen_block_copy_request(request);
}
break;
case BLKIF_OP_WRITE:
case BLKIF_OP_FLUSH_DISKCACHE:
default:
break;
}
request->status = request->aio_errors ? BLKIF_RSP_ERROR : BLKIF_RSP_OKAY;
switch (request->req.operation) {
case BLKIF_OP_WRITE:
case BLKIF_OP_FLUSH_DISKCACHE:
if (!request->req.nr_segments) {
break;
}
/* fall through */
case BLKIF_OP_READ:
if (request->status == BLKIF_RSP_OKAY) {
block_acct_done(blk_get_stats(dataplane->blk), &request->acct);
} else {
block_acct_failed(blk_get_stats(dataplane->blk), &request->acct);
}
break;
case BLKIF_OP_DISCARD:
default:
break;
}
xen_block_complete_request(request);
if (dataplane->more_work) {
qemu_bh_schedule(dataplane->bh);
}
done:
aio_context_release(dataplane->ctx);
}
static bool xen_block_split_discard(XenBlockRequest *request,
blkif_sector_t sector_number,
uint64_t nr_sectors)
{
XenBlockDataPlane *dataplane = request->dataplane;
int64_t byte_offset;
int byte_chunk;
uint64_t byte_remaining;
uint64_t sec_start = sector_number;
uint64_t sec_count = nr_sectors;
/* Wrap around, or overflowing byte limit? */
if (sec_start + sec_count < sec_count ||
sec_start + sec_count > INT64_MAX / dataplane->sector_size) {
return false;
}
byte_offset = sec_start * dataplane->sector_size;
byte_remaining = sec_count * dataplane->sector_size;
do {
byte_chunk = byte_remaining > BDRV_REQUEST_MAX_BYTES ?
BDRV_REQUEST_MAX_BYTES : byte_remaining;
request->aio_inflight++;
blk_aio_pdiscard(dataplane->blk, byte_offset, byte_chunk,
xen_block_complete_aio, request);
byte_remaining -= byte_chunk;
byte_offset += byte_chunk;
} while (byte_remaining > 0);
return true;
}
static int xen_block_do_aio(XenBlockRequest *request)
{
XenBlockDataPlane *dataplane = request->dataplane;
if (request->req.nr_segments &&
(request->req.operation == BLKIF_OP_WRITE ||
request->req.operation == BLKIF_OP_FLUSH_DISKCACHE) &&
xen_block_copy_request(request)) {
goto err;
}
request->aio_inflight++;
if (request->presync) {
blk_aio_flush(request->dataplane->blk, xen_block_complete_aio,
request);
return 0;
}
switch (request->req.operation) {
case BLKIF_OP_READ:
qemu_iovec_add(&request->v, request->buf, request->size);
block_acct_start(blk_get_stats(dataplane->blk), &request->acct,
request->v.size, BLOCK_ACCT_READ);
request->aio_inflight++;
blk_aio_preadv(dataplane->blk, request->start, &request->v, 0,
xen_block_complete_aio, request);
break;
case BLKIF_OP_WRITE:
case BLKIF_OP_FLUSH_DISKCACHE:
if (!request->req.nr_segments) {
break;
}
qemu_iovec_add(&request->v, request->buf, request->size);
block_acct_start(blk_get_stats(dataplane->blk), &request->acct,
request->v.size,
request->req.operation == BLKIF_OP_WRITE ?
BLOCK_ACCT_WRITE : BLOCK_ACCT_FLUSH);
request->aio_inflight++;
blk_aio_pwritev(dataplane->blk, request->start, &request->v, 0,
xen_block_complete_aio, request);
break;
case BLKIF_OP_DISCARD:
{
struct blkif_request_discard *req = (void *)&request->req;
if (!xen_block_split_discard(request, req->sector_number,
req->nr_sectors)) {
goto err;
}
break;
}
default:
/* unknown operation (shouldn't happen -- parse catches this) */
goto err;
}
xen_block_complete_aio(request, 0);
return 0;
err:
request->status = BLKIF_RSP_ERROR;
xen_block_complete_request(request);
return -1;
}
static int xen_block_send_response(XenBlockRequest *request)
{
XenBlockDataPlane *dataplane = request->dataplane;
int send_notify = 0;
int have_requests = 0;
blkif_response_t *resp;
/* Place on the response ring for the relevant domain. */
switch (dataplane->protocol) {
case BLKIF_PROTOCOL_NATIVE:
resp = (blkif_response_t *)RING_GET_RESPONSE(
&dataplane->rings.native,
dataplane->rings.native.rsp_prod_pvt);
break;
case BLKIF_PROTOCOL_X86_32:
resp = (blkif_response_t *)RING_GET_RESPONSE(
&dataplane->rings.x86_32_part,
dataplane->rings.x86_32_part.rsp_prod_pvt);
break;
case BLKIF_PROTOCOL_X86_64:
resp = (blkif_response_t *)RING_GET_RESPONSE(
&dataplane->rings.x86_64_part,
dataplane->rings.x86_64_part.rsp_prod_pvt);
break;
default:
return 0;
}
resp->id = request->req.id;
resp->operation = request->req.operation;
resp->status = request->status;
dataplane->rings.common.rsp_prod_pvt++;
RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&dataplane->rings.common,
send_notify);
if (dataplane->rings.common.rsp_prod_pvt ==
dataplane->rings.common.req_cons) {
/*
* Tail check for pending requests. Allows frontend to avoid
* notifications if requests are already in flight (lower
* overheads and promotes batching).
*/
RING_FINAL_CHECK_FOR_REQUESTS(&dataplane->rings.common,
have_requests);
} else if (RING_HAS_UNCONSUMED_REQUESTS(&dataplane->rings.common)) {
have_requests = 1;
}
if (have_requests) {
dataplane->more_work++;
}
return send_notify;
}
static int xen_block_get_request(XenBlockDataPlane *dataplane,
XenBlockRequest *request, RING_IDX rc)
{
switch (dataplane->protocol) {
case BLKIF_PROTOCOL_NATIVE: {
blkif_request_t *req =
RING_GET_REQUEST(&dataplane->rings.native, rc);
memcpy(&request->req, req, sizeof(request->req));
break;
}
case BLKIF_PROTOCOL_X86_32: {
blkif_x86_32_request_t *req =
RING_GET_REQUEST(&dataplane->rings.x86_32_part, rc);
blkif_get_x86_32_req(&request->req, req);
break;
}
case BLKIF_PROTOCOL_X86_64: {
blkif_x86_64_request_t *req =
RING_GET_REQUEST(&dataplane->rings.x86_64_part, rc);
blkif_get_x86_64_req(&request->req, req);
break;
}
}
/* Prevent the compiler from accessing the on-ring fields instead. */
barrier();
return 0;
}
/*
* Threshold of in-flight requests above which we will start using
* blk_io_plug()/blk_io_unplug() to batch requests.
*/
#define IO_PLUG_THRESHOLD 1
static bool xen_block_handle_requests(XenBlockDataPlane *dataplane)
{
RING_IDX rc, rp;
XenBlockRequest *request;
int inflight_atstart = dataplane->requests_inflight;
int batched = 0;
bool done_something = false;
dataplane->more_work = 0;
rc = dataplane->rings.common.req_cons;
rp = dataplane->rings.common.sring->req_prod;
xen_rmb(); /* Ensure we see queued requests up to 'rp'. */
/*
* If there was more than IO_PLUG_THRESHOLD requests in flight
* when we got here, this is an indication that there the bottleneck
* is below us, so it's worth beginning to batch up I/O requests
* rather than submitting them immediately. The maximum number
* of requests we're willing to batch is the number already in
* flight, so it can grow up to max_requests when the bottleneck
* is below us.
*/
if (inflight_atstart > IO_PLUG_THRESHOLD) {
blk_io_plug(dataplane->blk);
}
while (rc != rp) {
/* pull request from ring */
if (RING_REQUEST_CONS_OVERFLOW(&dataplane->rings.common, rc)) {
break;
}
request = xen_block_start_request(dataplane);
if (request == NULL) {
dataplane->more_work++;
break;
}
xen_block_get_request(dataplane, request, rc);
dataplane->rings.common.req_cons = ++rc;
done_something = true;
/* parse them */
if (xen_block_parse_request(request) != 0) {
switch (request->req.operation) {
case BLKIF_OP_READ:
block_acct_invalid(blk_get_stats(dataplane->blk),
BLOCK_ACCT_READ);
break;
case BLKIF_OP_WRITE:
block_acct_invalid(blk_get_stats(dataplane->blk),
BLOCK_ACCT_WRITE);
break;
case BLKIF_OP_FLUSH_DISKCACHE:
block_acct_invalid(blk_get_stats(dataplane->blk),
BLOCK_ACCT_FLUSH);
default:
break;
};
xen_block_complete_request(request);
continue;
}
if (inflight_atstart > IO_PLUG_THRESHOLD &&
batched >= inflight_atstart) {
blk_io_unplug(dataplane->blk);
}
xen_block_do_aio(request);
if (inflight_atstart > IO_PLUG_THRESHOLD) {
if (batched >= inflight_atstart) {
blk_io_plug(dataplane->blk);
batched = 0;
} else {
batched++;
}
}
}
if (inflight_atstart > IO_PLUG_THRESHOLD) {
blk_io_unplug(dataplane->blk);
}
return done_something;
}
static void xen_block_dataplane_bh(void *opaque)
{
XenBlockDataPlane *dataplane = opaque;
aio_context_acquire(dataplane->ctx);
xen_block_handle_requests(dataplane);
aio_context_release(dataplane->ctx);
}
static bool xen_block_dataplane_event(void *opaque)
{
XenBlockDataPlane *dataplane = opaque;
return xen_block_handle_requests(dataplane);
}
XenBlockDataPlane *xen_block_dataplane_create(XenDevice *xendev,
BlockBackend *blk,
unsigned int sector_size,
IOThread *iothread)
{
XenBlockDataPlane *dataplane = g_new0(XenBlockDataPlane, 1);
dataplane->xendev = xendev;
dataplane->blk = blk;
dataplane->sector_size = sector_size;
QLIST_INIT(&dataplane->inflight);
QLIST_INIT(&dataplane->freelist);
if (iothread) {
dataplane->iothread = iothread;
object_ref(OBJECT(dataplane->iothread));
dataplane->ctx = iothread_get_aio_context(dataplane->iothread);
} else {
dataplane->ctx = qemu_get_aio_context();
}
dataplane->bh = aio_bh_new(dataplane->ctx, xen_block_dataplane_bh,
dataplane);
return dataplane;
}
void xen_block_dataplane_destroy(XenBlockDataPlane *dataplane)
{
XenBlockRequest *request;
if (!dataplane) {
return;
}
while (!QLIST_EMPTY(&dataplane->freelist)) {
request = QLIST_FIRST(&dataplane->freelist);
QLIST_REMOVE(request, list);
qemu_iovec_destroy(&request->v);
qemu_vfree(request->buf);
g_free(request);
}
qemu_bh_delete(dataplane->bh);
if (dataplane->iothread) {
object_unref(OBJECT(dataplane->iothread));
}
g_free(dataplane);
}
void xen_block_dataplane_stop(XenBlockDataPlane *dataplane)
{
XenDevice *xendev;
if (!dataplane) {
return;
}
xendev = dataplane->xendev;
aio_context_acquire(dataplane->ctx);
if (dataplane->event_channel) {
/* Only reason for failure is a NULL channel */
xen_device_set_event_channel_context(xendev, dataplane->event_channel,
qemu_get_aio_context(),
&error_abort);
}
/* Xen doesn't have multiple users for nodes, so this can't fail */
blk_set_aio_context(dataplane->blk, qemu_get_aio_context(), &error_abort);
aio_context_release(dataplane->ctx);
/*
* Now that the context has been moved onto the main thread, cancel
* further processing.
*/
qemu_bh_cancel(dataplane->bh);
if (dataplane->event_channel) {
Error *local_err = NULL;
xen_device_unbind_event_channel(xendev, dataplane->event_channel,
&local_err);
dataplane->event_channel = NULL;
if (local_err) {
error_report_err(local_err);
}
}
if (dataplane->sring) {
Error *local_err = NULL;
xen_device_unmap_grant_refs(xendev, dataplane->sring,
dataplane->nr_ring_ref, &local_err);
dataplane->sring = NULL;
if (local_err) {
error_report_err(local_err);
}
}
g_free(dataplane->ring_ref);
dataplane->ring_ref = NULL;
}
void xen_block_dataplane_start(XenBlockDataPlane *dataplane,
const unsigned int ring_ref[],
unsigned int nr_ring_ref,
unsigned int event_channel,
unsigned int protocol,
Error **errp)
{
ERRP_GUARD();
XenDevice *xendev = dataplane->xendev;
AioContext *old_context;
unsigned int ring_size;
unsigned int i;
dataplane->nr_ring_ref = nr_ring_ref;
dataplane->ring_ref = g_new(unsigned int, nr_ring_ref);
for (i = 0; i < nr_ring_ref; i++) {
dataplane->ring_ref[i] = ring_ref[i];
}
dataplane->protocol = protocol;
ring_size = XC_PAGE_SIZE * dataplane->nr_ring_ref;
switch (dataplane->protocol) {
case BLKIF_PROTOCOL_NATIVE:
{
dataplane->max_requests = __CONST_RING_SIZE(blkif, ring_size);
break;
}
case BLKIF_PROTOCOL_X86_32:
{
dataplane->max_requests = __CONST_RING_SIZE(blkif_x86_32, ring_size);
break;
}
case BLKIF_PROTOCOL_X86_64:
{
dataplane->max_requests = __CONST_RING_SIZE(blkif_x86_64, ring_size);
break;
}
default:
error_setg(errp, "unknown protocol %u", dataplane->protocol);
return;
}
xen_device_set_max_grant_refs(xendev, dataplane->nr_ring_ref,
errp);
if (*errp) {
goto stop;
}
dataplane->sring = xen_device_map_grant_refs(xendev,
dataplane->ring_ref,
dataplane->nr_ring_ref,
PROT_READ | PROT_WRITE,
errp);
if (*errp) {
goto stop;
}
switch (dataplane->protocol) {
case BLKIF_PROTOCOL_NATIVE:
{
blkif_sring_t *sring_native = dataplane->sring;
BACK_RING_INIT(&dataplane->rings.native, sring_native, ring_size);
break;
}
case BLKIF_PROTOCOL_X86_32:
{
blkif_x86_32_sring_t *sring_x86_32 = dataplane->sring;
BACK_RING_INIT(&dataplane->rings.x86_32_part, sring_x86_32,
ring_size);
break;
}
case BLKIF_PROTOCOL_X86_64:
{
blkif_x86_64_sring_t *sring_x86_64 = dataplane->sring;
BACK_RING_INIT(&dataplane->rings.x86_64_part, sring_x86_64,
ring_size);
break;
}
}
dataplane->event_channel =
xen_device_bind_event_channel(xendev, event_channel,
xen_block_dataplane_event, dataplane,
errp);
if (*errp) {
goto stop;
}
old_context = blk_get_aio_context(dataplane->blk);
aio_context_acquire(old_context);
/* If other users keep the BlockBackend in the iothread, that's ok */
blk_set_aio_context(dataplane->blk, dataplane->ctx, NULL);
aio_context_release(old_context);
/* Only reason for failure is a NULL channel */
aio_context_acquire(dataplane->ctx);
xen_device_set_event_channel_context(xendev, dataplane->event_channel,
dataplane->ctx, &error_abort);
aio_context_release(dataplane->ctx);
return;
stop:
xen_block_dataplane_stop(dataplane);
}
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