On Mon, Oct 19, 2015 at 02:24:37PM +0100, Suzuki K. Poulose wrote: > At the end( Patches 19-24 ) , we add a new ABI to expose the CPU feature > registers to the user space via emulation of MRS. The system exposes only a > limited set of feature values (See the documentation patch) from the above > infrastructure. The feature bits that are not exposed are set to the 'safe > value' which implies 'not supported'. > > Apart from the selected feature registers, we expose MIDR_EL1 (Main > ID Register). The user should be aware that, reading MIDR_EL1 can be > tricky on a heterogeneous system (just like getcpu()). We export the > value of the current CPU where 'MRS' is executed. REVIDR is not exposed > via MRS, since we cannot guarantee atomic access to both MIDR and REVIDR > (task migration). So they both are exposed via sysfs under : > > /sys/devices/system/cpu/cpu$ID/identification/ > \- midr > \- revidr > > The ABI useful for the toolchains (e.g, gcc, dynamic linker, JIT) to make > better runtime decisions based on what is available.
I queued patches 1-18 (I haven't pushed them out yet as I've seen Dave sending some comments) and plan to merge them in 4.4. Patches 19-24 need wider review and input from user space folk (dynamic loader, JDK) on whether the ABI is right for them before we commit to maintaining it in the kernel. Thanks. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
