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f80fad16af
qemu/hw/block/dataplane/xen-block.c
David Woodhouse f80fad16af hw/xen: Pass grant ref to gnttab unmap operation 
The previous commit introduced redirectable gnttab operations fairly
much like-for-like, with the exception of the extra arguments to the
->open() call which were always NULL/0 anyway.

This *changes* the arguments to the ->unmap() operation to include the
original ref# that was mapped. Under real Xen it isn't necessary; all we
need to do from QEMU is munmap(), then the kernel will release the grant,
and Xen does the tracking/refcounting for the guest.

When we have emulated grant tables though, we need to do all that for
ourselves. So let's have the back ends keep track of what they mapped
and pass it in to the ->unmap() method for us.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
2023-03-07 17:04:30 +00:00

831 lines
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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->ring_ref,
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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