Sergey Fedorov <serge.f...@gmail.com> writes: > On 15/04/16 17:23, Alex Bennée wrote: >> This makes multi-threading the default for 32 bit ARM on x86. It has >> been tested with Debian Jessie as well as my extended KVM unit tests >> which stress the SMC and TB invalidation code. Those tests can be found >> at: >> >> https://github.com/stsquad/kvm-unit-tests/tree/mttcg/current-tests-v5 >> >> Signed-off-by: Alex Bennée <alex.ben...@linaro.org> >> --- >> cpus.c | 20 ++++++++++++++++---- >> 1 file changed, 16 insertions(+), 4 deletions(-) >> >> diff --git a/cpus.c b/cpus.c >> index 860e2a9..daa92c7 100644 >> --- a/cpus.c >> +++ b/cpus.c >> @@ -171,12 +171,24 @@ opts_init(tcg_register_config); >> >> static bool default_mttcg_enabled(void) >> { >> - /* >> - * TODO: Check if we have a chance to have MTTCG working on this >> guest/host. >> - * Basically is the atomic instruction implemented? Is there any >> - * memory ordering issue? >> + /* Checklist for enabling MTTCG on a given frontend/backend combination >> + * >> + * - Are atomics correctly modelled for an MTTCG environment > > - Are cross-CPU manipulations safe (e.g. TLB invalidation/flush from > target helper) > - Are TCG context manipulations safe (e.g. TB invalidation from target > helper)
OK > >> + * - If the backend is weakly ordered >> + * - has the front-end implemented explicit memory ordering ops >> + * - does the back-end generate code to ensure memory ordering >> */ >> +#if defined(__i386__) || defined(__x86_64__) >> + /* x86 backend is strongly ordered which helps a lot */ >> + #if defined(TARGET_ARM) >> + return true; >> + #else >> + return false; >> + #endif > > Is it okay to indent preprocessor lines this way? I think preprocessor > lines are better to stand out from regular code and could be indented > like this: > > #if defined(__foo__) > # if defined(BAR) > /* ... */ > # else > /* ... */ > # endif > #else > /* ... */ > #endif To be honest I was expecting more push-back on this because it is such an ugly way of solving the problem and expressing what a default on means. > > Kind regards, > Sergey > >> +#else >> + /* Until memory ordering implemented things will likely break */ >> return false; >> +#endif >> } >> >> void qemu_tcg_configure(QemuOpts *opts) -- Alex Bennée
