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: Sebastian Tanase <sebastian.tanase@openwide.fr>
Tested-by: Camille Bégué <camille.begue@openwide.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/cpus.c b/cpus.c
index 8291044..7e09538 100644
--- a/cpus.c
+++ b/cpus.c
@@ -476,25 +476,30 @@
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;
diff --git a/include/qemu-common.h b/include/qemu-common.h
index 04b0769..5d10ac2 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -108,6 +108,7 @@
/* 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 5a1b001..96516c1 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3011,9 +3011,9 @@
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 @@
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 f2621a5..a8029d5 100644
--- a/vl.c
+++ b/vl.c
@@ -183,6 +183,7 @@
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 @@
{
.name = "shift",
.type = QEMU_OPT_STRING,
+ }, {
+ .name = "align",
+ .type = QEMU_OPT_BOOL,
},
{ /* end of list */ }
},
