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xen/tools/libxc/xg_save_restore.h
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Shriram Rajagopalan f6b3d39f5d tools/libxc: Remus Checkpoint Compression 
Instead of sending dirty pages of guest memory as-is, use a simple compression
algorithm that sends a RLE-encoded XOR of the page against its last sent copy.
A small LRU cache is used to hold recently dirtied pages. Pagetable pages are
sent as-is, as they are canonicalized at sender side and uncanonicalized at
receiver.

[ Fixed up a conflict in sg_save_restore.h.  I had to increase the
  ID values used from -11 and -12 to -12 and -13 because -11 had
  been taken by ..._HVM_VIRIDIAN in the meantime. -iwj ]

Signed-off-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Acked-by: Brendan Cully <brendan@cs.ubc.ca>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
2011-12-01 15:36:15 +00:00

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/*
* Definitions and utilities for save / restore.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "xc_private.h"
#include <xen/foreign/x86_32.h>
#include <xen/foreign/x86_64.h>
/*
* SAVE/RESTORE/MIGRATE PROTOCOL
* =============================
*
* The general form of a stream of chunks is a header followed by a
* body consisting of a variable number of chunks (terminated by a
* chunk with type 0) followed by a trailer.
*
* For a rolling/checkpoint (e.g. remus) migration then the body and
* trailer phases can be repeated until an external event
* (e.g. failure) causes the process to terminate and commit to the
* most recent complete checkpoint.
*
* HEADER
* ------
*
* unsigned long : p2m_size
*
* extended-info (PV-only, optional):
*
* If first unsigned long == ~0UL then extended info is present,
* otherwise unsigned long is part of p2m. Note that p2m_size above
* does not include the length of the extended info.
*
* extended-info:
*
* unsigned long : signature == ~0UL
* uint32_t : number of bytes remaining in extended-info
*
* 1 or more extended-info blocks of form:
* char[4] : block identifier
* uint32_t : block data size
* bytes : block data
*
* defined extended-info blocks:
* "vcpu" : VCPU context info containing vcpu_guest_context_t.
* The precise variant of the context structure
* (e.g. 32 vs 64 bit) is distinguished by
* the block size.
* "extv" : Presence indicates use of extended VCPU context in
* tail, data size is 0.
*
* p2m (PV-only):
*
* consists of p2m_size bytes comprising an array of xen_pfn_t sized entries.
*
* BODY PHASE - Format A (for live migration or Remus without compression)
* ----------
*
* A series of chunks with a common header:
* int : chunk type
*
* If the chunk type is +ve then chunk contains guest memory data, and the
* type contains the number of pages in the batch:
*
* unsigned long[] : PFN array, length == number of pages in batch
* Each entry consists of XEN_DOMCTL_PFINFO_*
* in bits 31-28 and the PFN number in bits 27-0.
* page data : PAGE_SIZE bytes for each page marked present in PFN
* array
*
* If the chunk type is -ve then chunk consists of one of a number of
* metadata types. See definitions of XC_SAVE_ID_* below.
*
* If chunk type is 0 then body phase is complete.
*
*
* BODY PHASE - Format B (for Remus with compression)
* ----------
*
* A series of chunks with a common header:
* int : chunk type
*
* If the chunk type is +ve then chunk contains array of PFNs corresponding
* to guest memory and type contains the number of PFNs in the batch:
*
* unsigned long[] : PFN array, length == number of pages in batch
* Each entry consists of XEN_DOMCTL_PFINFO_*
* in bits 31-28 and the PFN number in bits 27-0.
*
* If the chunk type is -ve then chunk consists of one of a number of
* metadata types. See definitions of XC_SAVE_ID_* below.
*
* If the chunk type is -ve and equals XC_SAVE_ID_COMPRESSED_DATA, then the
* chunk consists of compressed page data, in the following format:
*
* unsigned long : Size of the compressed chunk to follow
* compressed data : variable length data of size indicated above.
* This chunk consists of compressed page data.
* The number of pages in one chunk depends on
* the amount of space available in the sender's
* output buffer.
*
* Format of compressed data:
* compressed_data = <deltas>*
* delta = <marker, run*>
* marker = (RUNFLAG|SKIPFLAG) bitwise-or RUNLEN [1 byte marker]
* RUNFLAG = 0
* SKIPFLAG = 1 << 7
* RUNLEN = 7-bit unsigned value indicating number of WORDS in the run
* run = string of bytes of length sizeof(WORD) * RUNLEN
*
* If marker contains RUNFLAG, then RUNLEN * sizeof(WORD) bytes of data following
* the marker is copied into the target page at the appropriate offset indicated by
* the offset_ptr
* If marker contains SKIPFLAG, then the offset_ptr is advanced
* by RUNLEN * sizeof(WORD).
*
* If chunk type is 0 then body phase is complete.
*
* There can be one or more chunks with type XC_SAVE_ID_COMPRESSED_DATA,
* containing compressed pages. The compressed chunks are collated to form
* one single compressed chunk for the entire iteration. The number of pages
* present in this final compressed chunk will be equal to the total number
* of valid PFNs specified by the +ve chunks.
*
* At the sender side, compressed pages are inserted into the output stream
* in the same order as they would have been if compression logic was absent.
*
* Until last iteration, the BODY is sent in Format A, to maintain live
* migration compatibility with receivers of older Xen versions.
* At the last iteration, if Remus compression was enabled, the sender sends
* a trigger, XC_SAVE_ID_ENABLE_COMPRESSION to tell the receiver to parse the
* BODY in Format B from the next iteration onwards.
*
* An example sequence of chunks received in Format B:
* +16 +ve chunk
* unsigned long[16] PFN array
* +100 +ve chunk
* unsigned long[100] PFN array
* +50 +ve chunk
* unsigned long[50] PFN array
*
* XC_SAVE_ID_COMPRESSED_DATA TAG
* N Length of compressed data
* N bytes of DATA Decompresses to 166 pages
*
* XC_SAVE_ID_* other xc save chunks
* 0 END BODY TAG
*
* Corner case with checkpoint compression:
* At sender side, after pausing the domain, dirty pages are usually
* copied out to a temporary buffer. After the domain is resumed,
* compression is done and the compressed chunk(s) are sent, followed by
* other XC_SAVE_ID_* chunks.
* If the temporary buffer gets full while scanning for dirty pages,
* the sender stops buffering of dirty pages, compresses the temporary
* buffer and sends the compressed data with XC_SAVE_ID_COMPRESSED_DATA.
* The sender then resumes the buffering of dirty pages and continues
* scanning for the dirty pages.
* For e.g., assume that the temporary buffer can hold 4096 pages and
* there are 5000 dirty pages. The following is the sequence of chunks
* that the receiver will see:
*
* +1024 +ve chunk
* unsigned long[1024] PFN array
* +1024 +ve chunk
* unsigned long[1024] PFN array
* +1024 +ve chunk
* unsigned long[1024] PFN array
* +1024 +ve chunk
* unsigned long[1024] PFN array
*
* XC_SAVE_ID_COMPRESSED_DATA TAG
* N Length of compressed data
* N bytes of DATA Decompresses to 4096 pages
*
* +4 +ve chunk
* unsigned long[4] PFN array
*
* XC_SAVE_ID_COMPRESSED_DATA TAG
* M Length of compressed data
* M bytes of DATA Decompresses to 4 pages
*
* XC_SAVE_ID_* other xc save chunks
* 0 END BODY TAG
*
* In other words, XC_SAVE_ID_COMPRESSED_DATA can be interleaved with
* +ve chunks arbitrarily. But at the receiver end, the following condition
* always holds true until the end of BODY PHASE:
* num(PFN entries +ve chunks) >= num(pages received in compressed form)
*
* TAIL PHASE
* ----------
*
* Content differs for PV and HVM guests.
*
* HVM TAIL:
*
* "Magic" pages:
* uint64_t : I/O req PFN
* uint64_t : Buffered I/O req PFN
* uint64_t : Store PFN
* Xen HVM Context:
* uint32_t : Length of context in bytes
* bytes : Context data
* Qemu context:
* char[21] : Signature:
* "QemuDeviceModelRecord" : Read Qemu save data until EOF
* "DeviceModelRecord0002" : uint32_t length field followed by that many
* bytes of Qemu save data
* "RemusDeviceModelState" : Currently the same as "DeviceModelRecord0002".
*
* PV TAIL:
*
* Unmapped PFN list : list of all the PFNs that were not in map at the close
* unsigned int : Number of unmapped pages
* unsigned long[] : PFNs of unmapped pages
*
* VCPU context data : A series of VCPU records, one per present VCPU
* Maximum and present map supplied in XC_SAVE_ID_VCPUINFO
* bytes: : VCPU context structure. Size is determined by size
* provided in extended-info header
* bytes[128] : Extended VCPU context (present IFF "extv" block
* present in extended-info header)
*
* Shared Info Page : 4096 bytes of shared info page
*/
#define XC_SAVE_ID_ENABLE_VERIFY_MODE -1 /* Switch to validation phase. */
#define XC_SAVE_ID_VCPU_INFO -2 /* Additional VCPU info */
#define XC_SAVE_ID_HVM_IDENT_PT -3 /* (HVM-only) */
#define XC_SAVE_ID_HVM_VM86_TSS -4 /* (HVM-only) */
#define XC_SAVE_ID_TMEM -5
#define XC_SAVE_ID_TMEM_EXTRA -6
#define XC_SAVE_ID_TSC_INFO -7
#define XC_SAVE_ID_HVM_CONSOLE_PFN -8 /* (HVM-only) */
#define XC_SAVE_ID_LAST_CHECKPOINT -9 /* Commit to restoring after completion of current iteration. */
#define XC_SAVE_ID_HVM_ACPI_IOPORTS_LOCATION -10
#define XC_SAVE_ID_HVM_VIRIDIAN -11
#define XC_SAVE_ID_COMPRESSED_DATA -12 /* Marker to indicate arrival of compressed data */
#define XC_SAVE_ID_ENABLE_COMPRESSION -13 /* Marker to enable compression logic at receiver side */
/*
** We process save/restore/migrate in batches of pages; the below
** determines how many pages we (at maximum) deal with in each batch.
*/
#define MAX_BATCH_SIZE 1024 /* up to 1024 pages (4MB) at a time */
/* When pinning page tables at the end of restore, we also use batching. */
#define MAX_PIN_BATCH 1024
/*
** Determine various platform information required for save/restore, in
** particular:
**
** - the maximum MFN on this machine, used to compute the size of
** the M2P table;
**
** - the starting virtual address of the the hypervisor; we use this
** to determine which parts of guest address space(s) do and don't
** require canonicalization during save/restore; and
**
** - the number of page-table levels for save/ restore. This should
** be a property of the domain, but for the moment we just read it
** from the hypervisor.
**
** - The width of a guest word (unsigned long), in bytes.
**
** Returns 1 on success, 0 on failure.
*/
static inline int get_platform_info(xc_interface *xch, uint32_t dom,
/* OUT */ unsigned long *max_mfn,
/* OUT */ unsigned long *hvirt_start,
/* OUT */ unsigned int *pt_levels,
/* OUT */ unsigned int *guest_width)
{
xen_capabilities_info_t xen_caps = "";
xen_platform_parameters_t xen_params;
DECLARE_DOMCTL;
if (xc_version(xch, XENVER_platform_parameters, &xen_params) != 0)
return 0;
if (xc_version(xch, XENVER_capabilities, &xen_caps) != 0)
return 0;
*max_mfn = xc_maximum_ram_page(xch);
*hvirt_start = xen_params.virt_start;
memset(&domctl, 0, sizeof(domctl));
domctl.domain = dom;
domctl.cmd = XEN_DOMCTL_get_address_size;
if ( do_domctl(xch, &domctl) != 0 )
return 0;
*guest_width = domctl.u.address_size.size / 8;
/* 64-bit tools will see the 64-bit hvirt_start, but 32-bit guests
* will be using the compat one. */
if ( *guest_width < sizeof (unsigned long) )
/* XXX need to fix up a way of extracting this value from Xen if
* XXX it becomes variable for domU */
*hvirt_start = 0xf5800000;
if (strstr(xen_caps, "xen-3.0-x86_64"))
/* Depends on whether it's a compat 32-on-64 guest */
*pt_levels = ( (*guest_width == 8) ? 4 : 3 );
else if (strstr(xen_caps, "xen-3.0-x86_32p"))
*pt_levels = 3;
else if (strstr(xen_caps, "xen-3.0-x86_32"))
*pt_levels = 2;
else
return 0;
return 1;
}
/*
** Save/restore deal with the mfn_to_pfn (M2P) and pfn_to_mfn (P2M) tables.
** The M2P simply holds the corresponding PFN, while the top bit of a P2M
** entry tell us whether or not the the PFN is currently mapped.
*/
#define PFN_TO_KB(_pfn) ((_pfn) << (PAGE_SHIFT - 10))
/*
** The M2P is made up of some number of 'chunks' of at least 2MB in size.
** The below definitions and utility function(s) deal with mapping the M2P
** regarldess of the underlying machine memory size or architecture.
*/
#define M2P_SHIFT L2_PAGETABLE_SHIFT_PAE
#define M2P_CHUNK_SIZE (1 << M2P_SHIFT)
#define M2P_SIZE(_m) ROUNDUP(((_m) * sizeof(xen_pfn_t)), M2P_SHIFT)
#define M2P_CHUNKS(_m) (M2P_SIZE((_m)) >> M2P_SHIFT)
/* Returns TRUE if the PFN is currently mapped */
#define is_mapped(pfn_type) (!((pfn_type) & 0x80000000UL))
#define GET_FIELD(_p, _f) ((dinfo->guest_width==8) ? ((_p)->x64._f) : ((_p)->x32._f))
#define SET_FIELD(_p, _f, _v) do { \
if (dinfo->guest_width == 8) \
(_p)->x64._f = (_v); \
else \
(_p)->x32._f = (_v); \
} while (0)
#define UNFOLD_CR3(_c) \
((uint64_t)((dinfo->guest_width == 8) \
? ((_c) >> 12) \
: (((uint32_t)(_c) >> 12) | ((uint32_t)(_c) << 20))))
#define FOLD_CR3(_c) \
((uint64_t)((dinfo->guest_width == 8) \
? ((uint64_t)(_c)) << 12 \
: (((uint32_t)(_c) << 12) | ((uint32_t)(_c) >> 20))))
#define MEMCPY_FIELD(_d, _s, _f) do { \
if (dinfo->guest_width == 8) \
memcpy(&(_d)->x64._f, &(_s)->x64._f,sizeof((_d)->x64._f)); \
else \
memcpy(&(_d)->x32._f, &(_s)->x32._f,sizeof((_d)->x32._f)); \
} while (0)
#define MEMSET_ARRAY_FIELD(_p, _f, _v) do { \
if (dinfo->guest_width == 8) \
memset(&(_p)->x64._f[0], (_v), sizeof((_p)->x64._f)); \
else \
memset(&(_p)->x32._f[0], (_v), sizeof((_p)->x32._f)); \
} while (0)
#ifndef MAX
#define MAX(_a, _b) ((_a) >= (_b) ? (_a) : (_b))
#endif
#ifndef MIN
#define MIN(_a, _b) ((_a) <= (_b) ? (_a) : (_b))
#endif
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