freebsd-dev/sys/amd64/vmm/vmm_snapshot.c
John Baldwin 483d953a86 Initial support for bhyve save and restore.
Save and restore (also known as suspend and resume) permits a snapshot
to be taken of a guest's state that can later be resumed.  In the
current implementation, bhyve(8) creates a UNIX domain socket that is
used by bhyvectl(8) to send a request to save a snapshot (and
optionally exit after the snapshot has been taken).  A snapshot
currently consists of two files: the first holds a copy of guest RAM,
and the second file holds other guest state such as vCPU register
values and device model state.

To resume a guest, bhyve(8) must be started with a matching pair of
command line arguments to instantiate the same set of device models as
well as a pointer to the saved snapshot.

While the current implementation is useful for several uses cases, it
has a few limitations.  The file format for saving the guest state is
tied to the ABI of internal bhyve structures and is not
self-describing (in that it does not communicate the set of device
models present in the system).  In addition, the state saved for some
device models closely matches the internal data structures which might
prove a challenge for compatibility of snapshot files across a range
of bhyve versions.  The file format also does not currently support
versioning of individual chunks of state.  As a result, the current
file format is not a fixed binary format and future revisions to save
and restore will break binary compatiblity of snapshot files.  The
goal is to move to a more flexible format that adds versioning,
etc. and at that point to commit to providing a reasonable level of
compatibility.  As a result, the current implementation is not enabled
by default.  It can be enabled via the WITH_BHYVE_SNAPSHOT=yes option
for userland builds, and the kernel option BHYVE_SHAPSHOT.

Submitted by:	Mihai Tiganus, Flavius Anton, Darius Mihai
Submitted by:	Elena Mihailescu, Mihai Carabas, Sergiu Weisz
Relnotes:	yes
Sponsored by:	University Politehnica of Bucharest
Sponsored by:	Matthew Grooms (student scholarships)
Sponsored by:	iXsystems
Differential Revision:	https://reviews.freebsd.org/D19495
2020-05-05 00:02:04 +00:00

142 lines
3.7 KiB
C

/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2016 Flavius Anton
* Copyright (c) 2016 Mihai Tiganus
* Copyright (c) 2016-2019 Mihai Carabas
* Copyright (c) 2017-2019 Darius Mihai
* Copyright (c) 2017-2019 Elena Mihailescu
* Copyright (c) 2018-2019 Sergiu Weisz
* All rights reserved.
* The bhyve-snapshot feature was developed under sponsorships
* from Matthew Grooms.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY NETAPP, INC ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL NETAPP, INC OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/systm.h>
#include <machine/vmm_snapshot.h>
void
vm_snapshot_buf_err(const char *bufname, const enum vm_snapshot_op op)
{
const char *opstr;
if (op == VM_SNAPSHOT_SAVE)
opstr = "save";
else if (op == VM_SNAPSHOT_RESTORE)
opstr = "restore";
else
opstr = "unknown";
printf("%s: snapshot-%s failed for %s\r\n", __func__, opstr, bufname);
}
int
vm_snapshot_buf(volatile void *data, size_t data_size,
struct vm_snapshot_meta *meta)
{
struct vm_snapshot_buffer *buffer;
int op;
void *nv_data;
nv_data = __DEVOLATILE(void *, data);
buffer = &meta->buffer;
op = meta->op;
if (buffer->buf_rem < data_size) {
printf("%s: buffer too small\r\n", __func__);
return (E2BIG);
}
if (op == VM_SNAPSHOT_SAVE)
copyout(nv_data, buffer->buf, data_size);
else if (op == VM_SNAPSHOT_RESTORE)
copyin(buffer->buf, nv_data, data_size);
else
return (EINVAL);
buffer->buf += data_size;
buffer->buf_rem -= data_size;
return (0);
}
size_t
vm_get_snapshot_size(struct vm_snapshot_meta *meta)
{
size_t length;
struct vm_snapshot_buffer *buffer;
buffer = &meta->buffer;
if (buffer->buf_size < buffer->buf_rem) {
printf("%s: Invalid buffer: size = %zu, rem = %zu\r\n",
__func__, buffer->buf_size, buffer->buf_rem);
length = 0;
} else {
length = buffer->buf_size - buffer->buf_rem;
}
return (length);
}
int
vm_snapshot_buf_cmp(volatile void *data, size_t data_size,
struct vm_snapshot_meta *meta)
{
struct vm_snapshot_buffer *buffer;
int op;
int ret;
void *_data = *(void **)(void *)&data;
buffer = &meta->buffer;
op = meta->op;
if (buffer->buf_rem < data_size) {
printf("%s: buffer too small\r\n", __func__);
ret = E2BIG;
goto done;
}
if (op == VM_SNAPSHOT_SAVE) {
ret = 0;
copyout(_data, buffer->buf, data_size);
} else if (op == VM_SNAPSHOT_RESTORE) {
ret = memcmp(_data, buffer->buf, data_size);
} else {
ret = EINVAL;
goto done;
}
buffer->buf += data_size;
buffer->buf_rem -= data_size;
done:
return (ret);
}