Re: [dpdk-dev] DPDK cpuflag check failure

[Neil Horman <nhorman@tuxdriver.com>]

On Sun, Sep 28, 2014 at 07:39:57AM +0000, Zhang, Jerry wrote:
> Hi all, 
> 
> 	Do you know why DPDK(shared library) constructor function rte_cpu_check_supported() needs to check some unnecessary CPU flags which is not used by current DPDK such as "AES"?
>      
>     On Hehalem platform with GCC4.8, using shard DPDK library, it will report AES is not supported. But actually AES instructions is not used by current DPDK.
> 

The function you reference is meant to assert that all the cpu features that
were enabled during the build are supported on the processor.  I expect you
enabled the crypto test, and as such the AES instructions were enabled in the
build.  disable the examples build and you'll probably be ok.
Neil


>     Thanks!
> 
> #ifndef __INTEL_COMPILER
> void __attribute__ ((__constructor__))
> #else
> void
> #endif
> rte_cpu_check_supported(void)
> {
> 	/* This is generated at compile-time by the build system */
> 	static const enum rte_cpu_flag_t compile_time_flags[] = {
> 			RTE_COMPILE_TIME_CPUFLAGS
> 	};
> 	unsigned i;
> 	int ret;
> 
> 	for (i = 0; i < sizeof(compile_time_flags)/sizeof(compile_time_flags[0]); i++) {
> 		ret = rte_cpu_get_flag_enabled(compile_time_flags[i]);
> 
> 		if (ret < 0) {
> 			fprintf(stderr,
> 				"ERROR: CPU feature flag lookup failed with error %d\n",
> 				ret);
> 			exit(1);
> 		}
> 		if (!ret) {
> 			fprintf(stderr,
> 			        "ERROR: This system does not support \"%s\".\n"
> 			        "Please check that RTE_MACHINE is set correctly.\n",
> 			        cpu_feature_table[compile_time_flags[i]].name);
> 			exit(1);
> 		}
> 	}
> }