Commit a8bfac37 authored by Sebastian Tanase's avatar Sebastian Tanase Committed by Paolo Bonzini
Browse files

icount: Add align option to icount 



The align option is used for activating the align algorithm
in order to synchronise the host clock and the guest clock.

Signed-off-by: default avatarSebastian Tanase <sebastian.tanase@openwide.fr>
Tested-by: default avatarCamille Bégué <camille.begue@openwide.fr>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 1ad9580b

cpus.c

+12 −7
Original line number Diff line number Diff line
@@ -476,25 +476,30 @@ static const VMStateDescription vmstate_timers = { 
void configure_icount(QemuOpts *opts, Error **errp)

{

    const char *option;

    char *rem_str = NULL;



    seqlock_init(&timers_state.vm_clock_seqlock, NULL);

    vmstate_register(NULL, 0, &vmstate_timers, &timers_state);

    option = qemu_opt_get(opts, "shift");

    if (!option) {

        return;

        if (qemu_opt_get(opts, "align") != NULL) {

            error_setg(errp, "Please specify shift option when using align");

        }

    /* When using -icount shift, the shift option will be

       misinterpreted as a boolean */

    if (strcmp(option, "on") == 0 || strcmp(option, "off") == 0) {

        error_setg(errp, "The shift option must be a number or auto");

        return;

    }



    icount_align_option = qemu_opt_get_bool(opts, "align", false);

    icount_warp_timer = timer_new_ns(QEMU_CLOCK_REALTIME,

                                          icount_warp_rt, NULL);

    if (strcmp(option, "auto") != 0) {

        icount_time_shift = strtol(option, NULL, 0);

        errno = 0;

        icount_time_shift = strtol(option, &rem_str, 0);

        if (errno != 0 || *rem_str != '\0' || !strlen(option)) {

            error_setg(errp, "icount: Invalid shift value");

        }

        use_icount = 1;

        return;

    } else if (icount_align_option) {

        error_setg(errp, "shift=auto and align=on are incompatible");

    }



    use_icount = 2;

include/qemu-common.h

+1 −0
Original line number Diff line number Diff line
@@ -108,6 +108,7 @@ static inline char *realpath(const char *path, char *resolved_path) 
/* icount */

void configure_icount(QemuOpts *opts, Error **errp);

extern int use_icount;

extern int icount_align_option;



#include "qemu/osdep.h"

#include "qemu/bswap.h"

qemu-options.hx

+13 −2
Original line number Diff line number Diff line
@@ -3011,9 +3011,9 @@ re-inject them. 
ETEXI



DEF("icount", HAS_ARG, QEMU_OPTION_icount, \

    "-icount [shift=N|auto]\n" \

    "-icount [shift=N|auto][,align=on|off]\n" \

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

    "                instruction\n", QEMU_ARCH_ALL)

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

STEXI

@item -icount [shift=@var{N}|auto]

@findex -icount
@@ -3026,6 +3026,17 @@ Note that while this option can give deterministic behavior, it does not 
provide cycle accurate emulation.  Modern CPUs contain superscalar out of

order cores with complex cache hierarchies.  The number of instructions

executed often has little or no correlation with actual performance.



@option{align=on} will activate the delay algorithm which will try to

to synchronise the host clock and the virtual clock. The goal is to

have a guest running at the real frequency imposed by the shift option.

Whenever the guest clock is behind the host clock and if

@option{align=on} is specified then we print a messsage to the user

to inform about the delay.

Currently this option does not work when @option{shift} is @code{auto}.

Note: The sync algorithm will work for those shift values for which

the guest clock runs ahead of the host clock. Typically this happens

when the shift value is high (how high depends on the host machine).

ETEXI



DEF("watchdog", HAS_ARG, QEMU_OPTION_watchdog, \

vl.c

+4 −0
Original line number Diff line number Diff line
@@ -183,6 +183,7 @@ uint8_t *boot_splash_filedata; 
size_t boot_splash_filedata_size;

uint8_t qemu_extra_params_fw[2];



int icount_align_option;

typedef struct FWBootEntry FWBootEntry;



struct FWBootEntry {
@@ -546,6 +547,9 @@ static QemuOptsList qemu_icount_opts = { 
        {

            .name = "shift",

            .type = QEMU_OPT_STRING,

        }, {

            .name = "align",

            .type = QEMU_OPT_BOOL,

        },

        { /* end of list */ }

    },