d3e4e51223
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
90 lines
3.4 KiB
C
90 lines
3.4 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (c) 2013 Peter Grehan <grehan@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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/*
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* The block API to be used by bhyve block-device emulations. The routines
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* are thread safe, with no assumptions about the context of the completion
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* callback - it may occur in the caller's context, or asynchronously in
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* another thread.
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*/
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#ifndef _BLOCK_IF_H_
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#define _BLOCK_IF_H_
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#include <sys/uio.h>
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#include <sys/unistd.h>
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struct vm_snapshot_meta;
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/*
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* BLOCKIF_IOV_MAX is the maximum number of scatter/gather entries in
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* a single request. BLOCKIF_RING_MAX is the maxmimum number of
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* pending requests that can be queued.
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*/
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#define BLOCKIF_IOV_MAX 128 /* not practical to be IOV_MAX */
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#define BLOCKIF_RING_MAX 128
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struct blockif_req {
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int br_iovcnt;
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off_t br_offset;
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ssize_t br_resid;
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void (*br_callback)(struct blockif_req *req, int err);
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void *br_param;
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struct iovec br_iov[BLOCKIF_IOV_MAX];
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};
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struct blockif_ctxt;
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struct blockif_ctxt *blockif_open(const char *optstr, const char *ident);
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off_t blockif_size(struct blockif_ctxt *bc);
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void blockif_chs(struct blockif_ctxt *bc, uint16_t *c, uint8_t *h,
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uint8_t *s);
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int blockif_sectsz(struct blockif_ctxt *bc);
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void blockif_psectsz(struct blockif_ctxt *bc, int *size, int *off);
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int blockif_queuesz(struct blockif_ctxt *bc);
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int blockif_is_ro(struct blockif_ctxt *bc);
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int blockif_candelete(struct blockif_ctxt *bc);
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int blockif_read(struct blockif_ctxt *bc, struct blockif_req *breq);
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int blockif_write(struct blockif_ctxt *bc, struct blockif_req *breq);
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int blockif_flush(struct blockif_ctxt *bc, struct blockif_req *breq);
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int blockif_delete(struct blockif_ctxt *bc, struct blockif_req *breq);
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int blockif_cancel(struct blockif_ctxt *bc, struct blockif_req *breq);
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int blockif_close(struct blockif_ctxt *bc);
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#ifdef BHYVE_SNAPSHOT
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void blockif_pause(struct blockif_ctxt *bc);
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void blockif_resume(struct blockif_ctxt *bc);
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int blockif_snapshot_req(struct blockif_req *br,
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struct vm_snapshot_meta *meta);
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int blockif_snapshot(struct blockif_ctxt *bc,
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struct vm_snapshot_meta *meta);
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#endif
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#endif /* _BLOCK_IF_H_ */
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