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authorKONRAD Frederic <fred.konrad@greensocs.com>2017-02-23 18:29:08 +0000
committerAlex Bennée <alex.bennee@linaro.org>2017-02-24 10:32:45 +0000
commit8d4e9146b3568022ea5730d92841345d41275d66 (patch)
tree76c0c83af2e41e05956a2e29f1a60dc89208c5d3 /cpus.c
parent20937143145b8f5a4194e5c407731ba38797864e (diff)
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tcg: add options for enabling MTTCG
We know there will be cases where MTTCG won't work until additional work is done in the front/back ends to support. It will however be useful to be able to turn it on. As a result MTTCG will default to off unless the combination is supported. However the user can turn it on for the sake of testing. Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com> [AJB: move to -accel tcg,thread=multi|single, defaults] Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net>
Diffstat (limited to 'cpus.c')
-rw-r--r--cpus.c73
1 files changed, 73 insertions, 0 deletions
diff --git a/cpus.c b/cpus.c
index 0bcb5b5..c94b330 100644
--- a/cpus.c
+++ b/cpus.c
@@ -25,6 +25,7 @@
/* Needed early for CONFIG_BSD etc. */
#include "qemu/osdep.h"
#include "qemu-common.h"
+#include "qemu/config-file.h"
#include "cpu.h"
#include "monitor/monitor.h"
#include "qapi/qmp/qerror.h"
@@ -45,6 +46,7 @@
#include "qemu/main-loop.h"
#include "qemu/bitmap.h"
#include "qemu/seqlock.h"
+#include "tcg.h"
#include "qapi-event.h"
#include "hw/nmi.h"
#include "sysemu/replay.h"
@@ -150,6 +152,77 @@ typedef struct TimersState {
} TimersState;
static TimersState timers_state;
+bool mttcg_enabled;
+
+/*
+ * We default to false if we know other options have been enabled
+ * which are currently incompatible with MTTCG. Otherwise when each
+ * guest (target) has been updated to support:
+ * - atomic instructions
+ * - memory ordering primitives (barriers)
+ * they can set the appropriate CONFIG flags in ${target}-softmmu.mak
+ *
+ * Once a guest architecture has been converted to the new primitives
+ * there are two remaining limitations to check.
+ *
+ * - The guest can't be oversized (e.g. 64 bit guest on 32 bit host)
+ * - The host must have a stronger memory order than the guest
+ *
+ * It may be possible in future to support strong guests on weak hosts
+ * but that will require tagging all load/stores in a guest with their
+ * implicit memory order requirements which would likely slow things
+ * down a lot.
+ */
+
+static bool check_tcg_memory_orders_compatible(void)
+{
+#if defined(TCG_GUEST_DEFAULT_MO) && defined(TCG_TARGET_DEFAULT_MO)
+ return (TCG_GUEST_DEFAULT_MO & ~TCG_TARGET_DEFAULT_MO) == 0;
+#else
+ return false;
+#endif
+}
+
+static bool default_mttcg_enabled(void)
+{
+ QemuOpts *icount_opts = qemu_find_opts_singleton("icount");
+ const char *rr = qemu_opt_get(icount_opts, "rr");
+
+ if (rr || TCG_OVERSIZED_GUEST) {
+ return false;
+ } else {
+#ifdef TARGET_SUPPORTS_MTTCG
+ return check_tcg_memory_orders_compatible();
+#else
+ return false;
+#endif
+ }
+}
+
+void qemu_tcg_configure(QemuOpts *opts, Error **errp)
+{
+ const char *t = qemu_opt_get(opts, "thread");
+ if (t) {
+ if (strcmp(t, "multi") == 0) {
+ if (TCG_OVERSIZED_GUEST) {
+ error_setg(errp, "No MTTCG when guest word size > hosts");
+ } else {
+ if (!check_tcg_memory_orders_compatible()) {
+ error_report("Guest expects a stronger memory ordering "
+ "than the host provides");
+ error_printf("This may cause strange/hard to debug errors");
+ }
+ mttcg_enabled = true;
+ }
+ } else if (strcmp(t, "single") == 0) {
+ mttcg_enabled = false;
+ } else {
+ error_setg(errp, "Invalid 'thread' setting %s", t);
+ }
+ } else {
+ mttcg_enabled = default_mttcg_enabled();
+ }
+}
int64_t cpu_get_icount_raw(void)
{