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author | KONRAD Frederic <fred.konrad@greensocs.com> | 2017-02-23 18:29:08 +0000 |
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committer | Alex Bennée <alex.bennee@linaro.org> | 2017-02-24 10:32:45 +0000 |
commit | 8d4e9146b3568022ea5730d92841345d41275d66 (patch) | |
tree | 76c0c83af2e41e05956a2e29f1a60dc89208c5d3 /cpus.c | |
parent | 20937143145b8f5a4194e5c407731ba38797864e (diff) | |
download | qemu-8d4e9146b3568022ea5730d92841345d41275d66.zip qemu-8d4e9146b3568022ea5730d92841345d41275d66.tar.gz qemu-8d4e9146b3568022ea5730d92841345d41275d66.tar.bz2 |
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.c | 73 |
1 files changed, 73 insertions, 0 deletions
@@ -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) { |