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Disable SME on iOS #433

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Disable SME on iOS #433

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35 changes: 26 additions & 9 deletions src/arm/mach/init.c
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Original file line number Diff line number Diff line change
Expand Up @@ -599,19 +599,36 @@ void cpuinfo_arm_mach_init(void) {
}

cpuinfo_isa.i8mm = get_sys_info_by_name("hw.optional.arm.FEAT_I8MM") != 0;
cpuinfo_isa.sme = get_sys_info_by_name("hw.optional.arm.FEAT_SME") != 0;
cpuinfo_isa.sme2 = get_sys_info_by_name("hw.optional.arm.FEAT_SME2") != 0;
cpuinfo_isa.sme2p1 = get_sys_info_by_name("hw.optional.arm.FEAT_SME2p1") != 0;
cpuinfo_isa.sme_i16i32 = get_sys_info_by_name("hw.optional.arm.SME_I16I32") != 0;
cpuinfo_isa.sme_bi32i32 = get_sys_info_by_name("hw.optional.arm.SME_BI32I32") != 0;
cpuinfo_isa.sme_b16b16 = get_sys_info_by_name("hw.optional.arm.FEAT_SME_B16B16") != 0;
cpuinfo_isa.sme_f16f16 = get_sys_info_by_name("hw.optional.arm.FEAT_SME_F16F16") != 0;

// An Apple processor may have SME hardware (e.g. A18/A19), but the XNU kernel
// only enables EL0 execution if sme_max_svl_b > 0.
// macOS and iPadOS (e.g. on M4) support and enable user-mode SME, but iOS
// disables user-mode SME, which causes SMSTART to trigger an EXC_BAD_INSTRUCTION fault.
const uint32_t smelen = get_sys_info_by_name("hw.optional.arm.sme_max_svl_b");
if (smelen > 0) {
cpuinfo_isa.sme = get_sys_info_by_name("hw.optional.arm.FEAT_SME") != 0;
cpuinfo_isa.sme2 = get_sys_info_by_name("hw.optional.arm.FEAT_SME2") != 0;
cpuinfo_isa.sme2p1 = get_sys_info_by_name("hw.optional.arm.FEAT_SME2p1") != 0;
cpuinfo_isa.sme_i16i32 = get_sys_info_by_name("hw.optional.arm.SME_I16I32") != 0;
cpuinfo_isa.sme_bi32i32 = get_sys_info_by_name("hw.optional.arm.SME_BI32I32") != 0;
cpuinfo_isa.sme_b16b16 = get_sys_info_by_name("hw.optional.arm.FEAT_SME_B16B16") != 0;
cpuinfo_isa.sme_f16f16 = get_sys_info_by_name("hw.optional.arm.FEAT_SME_F16F16") != 0;
cpuinfo_isa.smelen = smelen;
} else {
cpuinfo_isa.sme = false;
cpuinfo_isa.sme2 = false;
cpuinfo_isa.sme2p1 = false;
cpuinfo_isa.sme_i16i32 = false;
cpuinfo_isa.sme_bi32i32 = false;
cpuinfo_isa.sme_b16b16 = false;
cpuinfo_isa.sme_f16f16 = false;
cpuinfo_isa.smelen = 0;
}

cpuinfo_isa.fp8 = get_sys_info_by_name("hw.optional.arm.FEAT_FP8") != 0;
cpuinfo_isa.f8dot = get_sys_info_by_name("hw.optional.arm.FEAT_FP8DOT4") != 0;
cpuinfo_isa.f8mm = get_sys_info_by_name("hw.optional.arm.FEAT_F8F32MM") != 0;

cpuinfo_isa.smelen = get_sys_info_by_name("hw.optional.arm.sme_max_svl_b");

uint32_t num_clusters = 1;
for (uint32_t i = 0; i < mach_topology.cores; i++) {
cores[i] = (struct cpuinfo_core){
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