On 3/12/2024 2:26 AM, Muhammad Usama Anjum wrote:
How can we check if AMX is available or not?
After a successful check_cpuid_xsave(), examining CPUID(eax=0xd, ecx=0) EDX: EAX, which reports the support bits of XCR0, can give assurance of AMX availability. Perhaps, this change is considerable on top of your patch:
static int check_cpuid_xtiledata(void) { uint32_t eax, ebx, ecx, edx; + uint64_t xfeatures;
__cpuid_count(CPUID_LEAF_XSTATE, CPUID_SUBLEAF_XSTATE_USER, eax, ebx, ecx, edx);
+ xfeatures = eax + ((uint64_t)edx << 32); + if ((xfeatures & XFEATURE_MASK_XTILE) != XFEATURE_MASK_XTILE) { + ksft_print_msg("no AMX support\n"); + return -1; + }
Nevertheless, I still believe that using arch_prctl(ARCH_GET_XCOMP_SUPP, ...) remains a simple and legitimate approach for directly checking dynamic feature support from the kernel: https://docs.kernel.org/arch/x86/xstate.html
Thanks, Chang