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.tan...@openwide.fr>
Tested-by: Camille Bégué <camille.be...@openwide.fr>
---
cpus.c | 13 +++++++++++++
include/qemu-common.h | 1 +
qemu-options.hx | 15 +++++++++++++--
vl.c | 4 ++++
4 files changed, 31 insertions(+), 2 deletions(-)
diff --git a/cpus.c b/cpus.c
index dcca96a..3fa8ce7 100644
--- a/cpus.c
+++ b/cpus.c
@@ -448,13 +448,24 @@ void configure_icount(QemuOpts *opts, Error **errp)
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;
}
+ icount_align_option = qemu_opt_get_bool(opts, "align", false);
/* 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");
}
+ /* When using icount [shift=]N|auto -icount align, shift becomes
+ align therefore we have to specify align=on|off.
+ We do however inform the user whenever the case. */
+ if (strcmp(option, "align") == 0) {
+ error_setg(errp, "Please specify align=on or off so as not "
+ "to create confusion between the shift and align options");
+ }
icount_warp_timer = timer_new_ns(QEMU_CLOCK_REALTIME,
icount_warp_rt, NULL);
@@ -462,6 +473,8 @@ void configure_icount(QemuOpts *opts, Error **errp)
icount_time_shift = strtol(option, NULL, 0);
use_icount = 1;
return;
+ } else if (icount_align_option) {
+ error_setg(errp, "shift=auto and align=on are incompatible");
}
use_icount = 2;
diff --git a/include/qemu-common.h b/include/qemu-common.h
index cc346ec..860bb15 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -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"
diff --git a/qemu-options.hx b/qemu-options.hx
index 143def4..379d932 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -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, \
diff --git a/vl.c b/vl.c
index 103027f..d270070 100644
--- a/vl.c
+++ b/vl.c
@@ -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 */ }
},
--
2.0.0.rc2
