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icount: Add align option to icount

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

Signed-off-by: Sebastian Tanase <sebastian.tanase@openwide.fr>
Tested-by: Camille Bégué <camille.begue@openwide.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sebastian Tanase 2014-07-25 11:56:29 +02:00 committed by Paolo Bonzini
parent 1ad9580bd7
commit a8bfac3708
4 changed files with 30 additions and 9 deletions
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19
cpus.c
View File

@ -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) {
if (qemu_opt_get(opts, "align") != NULL) {
error_setg(errp, "Please specify shift option when using align");
}
return;
}
/* 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");
}
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;

1
include/qemu-common.h
View File

@ -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"

15
qemu-options.hx
View File

@ -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, \

4
vl.c
View File

@ -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 */ }
},