Commit 9c2037d0 authored by Pavel Dovgalyuk's avatar Pavel Dovgalyuk Committed by Paolo Bonzini
Browse files

replay: save/load initial state 



This patch implements initial vmstate creation or loading at the start
of record/replay. It is needed for rewinding the execution in the replay mode.

v4 changes:
 - snapshots are not created by default anymore

v3 changes:
 - added rrsnapshot option

Signed-off-by: default avatarPavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20170124071746.4572.61449.stgit@PASHA-ISP>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent ac8c19ba

docs/replay.txt

+16 −0
Original line number Diff line number Diff line
@@ -196,6 +196,22 @@ is recorded to the log. In replay phase the queue is matched with 
events read from the log. Therefore block devices requests are processed

deterministically.



Snapshotting

------------



New VM snapshots may be created in replay mode. They can be used later

to recover the desired VM state. All VM states created in replay mode

are associated with the moment of time in the replay scenario.

After recovering the VM state replay will start from that position.



Default starting snapshot name may be specified with icount field

rrsnapshot as follows:

 -icount shift=7,rr=record,rrfile=replay.bin,rrsnapshot=snapshot_name



This snapshot is created at start of recording and restored at start

of replaying. It also can be loaded while replaying to roll back

the execution.



Network devices

---------------

include/sysemu/replay.h

+9 −0
Original line number Diff line number Diff line
@@ -43,6 +43,9 @@ typedef struct ReplayNetState ReplayNetState; 


extern ReplayMode replay_mode;



/* Name of the initial VM snapshot */

extern char *replay_snapshot;



/* Replay process control functions */



/*! Enables recording or saving event log with specified parameters */
@@ -149,4 +152,10 @@ void replay_unregister_net(ReplayNetState *rns); 
void replay_net_packet_event(ReplayNetState *rns, unsigned flags,

                             const struct iovec *iov, int iovcnt);



/* VM state operations */



/*! Called at the start of execution.

    Loads or saves initial vmstate depending on execution mode. */

void replay_vmstate_init(void);



#endif

qemu-options.hx

+6 −2
Original line number Diff line number Diff line
@@ -3400,12 +3400,12 @@ re-inject them. 
ETEXI



DEF("icount", HAS_ARG, QEMU_OPTION_icount, \

    "-icount [shift=N|auto][,align=on|off][,sleep=on|off,rr=record|replay,rrfile=<filename>]\n" \

    "-icount [shift=N|auto][,align=on|off][,sleep=on|off,rr=record|replay,rrfile=<filename>,rrsnapshot=<snapshot>]\n" \

    "                enable virtual instruction counter with 2^N clock ticks per\n" \

    "                instruction, enable aligning the host and virtual clocks\n" \

    "                or disable real time cpu sleeping\n", QEMU_ARCH_ALL)

STEXI

@item -icount [shift=@var{N}|auto][,rr=record|replay,rrfile=@var{filename}]

@item -icount [shift=@var{N}|auto][,rr=record|replay,rrfile=@var{filename},rrsnapshot=@var{snapshot}]

@findex -icount

Enable virtual instruction counter.  The virtual cpu will execute one

instruction every 2^@var{N} ns of virtual time.  If @code{auto} is specified
@@ -3438,6 +3438,10 @@ when the shift value is high (how high depends on the host machine). 
When @option{rr} option is specified deterministic record/replay is enabled.

Replay log is written into @var{filename} file in record mode and

read from this file in replay mode.



Option rrsnapshot is used to create new vm snapshot named @var{snapshot}

at the start of execution recording. In replay mode this option is used

to load the initial VM state.

ETEXI



DEF("watchdog", HAS_ARG, QEMU_OPTION_watchdog, \

replay/replay-snapshot.c

+17 −0
Original line number Diff line number Diff line
@@ -59,3 +59,20 @@ void replay_vmstate_register(void) 
{

    vmstate_register(NULL, 0, &vmstate_replay, &replay_state);

}



void replay_vmstate_init(void)

{

    if (replay_snapshot) {

        if (replay_mode == REPLAY_MODE_RECORD) {

            if (save_vmstate(cur_mon, replay_snapshot) != 0) {

                error_report("Could not create snapshot for icount record");

                exit(1);

            }

        } else if (replay_mode == REPLAY_MODE_PLAY) {

            if (load_vmstate(replay_snapshot) != 0) {

                error_report("Could not load snapshot for icount replay");

                exit(1);

            }

        }

    }

}

replay/replay.c

+5 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 
#define HEADER_SIZE                 (sizeof(uint32_t) + sizeof(uint64_t))



ReplayMode replay_mode = REPLAY_MODE_NONE;

char *replay_snapshot;



/* Name of replay file  */

static char *replay_filename;
@@ -292,6 +293,7 @@ void replay_configure(QemuOpts *opts) 
        exit(1);

    }



    replay_snapshot = g_strdup(qemu_opt_get(opts, "rrsnapshot"));

    replay_vmstate_register();

    replay_enable(fname, mode);
@@ -346,6 +348,9 @@ void replay_finish(void) 
        replay_filename = NULL;

    }



    g_free(replay_snapshot);

    replay_snapshot = NULL;



    replay_finish_events();

    replay_mutex_destroy();

}