HostFeatures: Moves MIDR querying to the frontend

The MIDR querying is inherently OS specific and needs a bit of special
casing. Instead let the frontend inform FEXCore how many CPU cores there
are and their MIDRs instead.

This lets us keep the Linux specific code in the frontend.

FEXCore/Source/Interface/Core/CPUID.cpp

@@ -114,27 +114,16 @@ void CPUIDEmu::SetupHostHybridFlag() {
 
   uint64_t MIDR {};
   for (size_t i = 0; i < Cores; ++i) {
-    std::error_code ec {};
-    fextl::string MIDRPath = fextl::fmt::format("/sys/devices/system/cpu/cpu{}/regs/identification/midr_el1", i);
-
-    std::array<char, 18> Data;
-    // Needs to be a fixed size since depending on kernel it will try to read a full page of data and fail
-    // Only read 18 bytes for a 64bit value prefixed with 0x
-    if (FEXCore::FileLoading::LoadFileToBuffer(MIDRPath, Data) == sizeof(Data)) {
-      uint64_t NewMIDR {};
-      std::string_view MIDRView(Data.data(), sizeof(Data));
-      if (FEXCore::StrConv::Conv(MIDRView, &NewMIDR)) {
-        if (MIDR != 0 && MIDR != NewMIDR) {
-          // CPU mismatch, claim hybrid
-          Hybrid = true;
-        }
-
-        // Truncate to 32-bits, top 32-bits are all reserved in MIDR
-        PerCPUData[i].ProductName = ProductNames::ARM_UNKNOWN;
-        PerCPUData[i].MIDR = NewMIDR;
-        MIDR = NewMIDR;
-      }
+    auto NewMIDR = CTX->HostFeatures.CPUMIDRs[i];
+    if (MIDR != 0 && MIDR != NewMIDR) {
+      // CPU mismatch, claim hybrid
+      Hybrid = true;
     }
+
+    // Truncate to 32-bits, top 32-bits are all reserved in MIDR
+    PerCPUData[i].ProductName = ProductNames::ARM_UNKNOWN;
+    PerCPUData[i].MIDR = NewMIDR;
+    MIDR = NewMIDR;
   }
 
   struct CPUMIDR {
@@ -1185,7 +1174,7 @@ FEXCore::CPUID::XCRResults CPUIDEmu::XCRFunction_0h() const {
 
 CPUIDEmu::CPUIDEmu(const FEXCore::Context::ContextImpl* ctx)
   : CTX {ctx} {
-  Cores = FEXCore::CPUInfo::CalculateNumberOfCPUs();
+  Cores = CTX->HostFeatures.CPUMIDRs.size();
 
   // Setup some state tracking
   SetupHostHybridFlag();

FEXCore/include/FEXCore/Core/HostFeatures.h

@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: MIT
 #pragma once
+
+#include <FEXCore/fextl/vector.h>
 #include <cstdint>
 
 namespace FEXCore {
@@ -37,5 +39,9 @@ struct HostFeatures {
   // Float exception behaviour
   bool SupportsAFP {};
   bool SupportsFloatExceptions {};
+
+  // MIDR information
+  // Also used for determining number of CPU cores for CPUID
+  fextl::vector<uint32_t> CPUMIDRs;
 };
 } // namespace FEXCore

Source/Common/HostFeatures.cpp

@@ -3,6 +3,9 @@
 
 #include <FEXCore/Config/Config.h>
 #include <FEXCore/Core/HostFeatures.h>
+#include <FEXCore/Utils/CPUInfo.h>
+#include <FEXCore/Utils/FileLoading.h>
+#include <FEXCore/Utils/StringUtils.h>
 
 #ifdef _M_X86_64
 #define XBYAK64
@@ -17,6 +20,28 @@
 
 namespace FEX {
 
+void FillMIDRInformationViaLinux(FEXCore::HostFeatures* Features) {
+  auto Cores = FEXCore::CPUInfo::CalculateNumberOfCPUs();
+  Features->CPUMIDRs.resize(Cores);
+#ifdef _M_ARM_64
+  for (size_t i = 0; i < Cores; ++i) {
+    std::error_code ec {};
+    fextl::string MIDRPath = fextl::fmt::format("/sys/devices/system/cpu/cpu{}/regs/identification/midr_el1", i);
+    std::array<char, 18> Data;
+    // Needs to be a fixed size since depending on kernel it will try to read a full page of data and fail
+    // Only read 18 bytes for a 64bit value prefixed with 0x
+    if (FEXCore::FileLoading::LoadFileToBuffer(MIDRPath, Data) == sizeof(Data)) {
+      uint64_t MIDR {};
+      auto Results = std::from_chars(Data.data() + 2, Data.data() + sizeof(Data), MIDR, 16);
+      if (Results.ec == std::errc()) {
+        // Truncate to 32-bits, top 32-bits are all reserved in MIDR
+        Features->CPUMIDRs[i] = static_cast<uint32_t>(MIDR);
+      }
+    }
+  }
+#endif
+}
+
 #ifdef _M_ARM_64
 #define GetSysReg(name, reg)                         \
   static uint64_t Get_##name() {                     \
@@ -603,6 +628,8 @@ FEXCore::HostFeatures FetchHostFeatures() {
   __asm volatile("mrs %[midr], midr_el1" : [midr] "=r"(MIDR));
 #endif
 
-  return FetchHostFeatures(Features, true, CTR, MIDR);
+  auto HostFeatures = FetchHostFeatures(Features, true, CTR, MIDR);
+  FillMIDRInformationViaLinux(&HostFeatures);
+  return HostFeatures;
 }
 } // namespace FEX

Source/Common/HostFeatures.h

@@ -623,6 +623,8 @@ class CPUFeatures {
   }
 };
 
+void FillMIDRInformationViaLinux(FEXCore::HostFeatures* Features);
+
 FEXCore::HostFeatures FetchHostFeatures(FEX::CPUFeatures& Features, bool SupportsCacheMaintenanceOps, uint64_t CTR, uint64_t MIDR);
 FEXCore::HostFeatures FetchHostFeatures();
 } // namespace FEX

Source/Windows/Common/CPUFeatures.cpp

@@ -2,13 +2,21 @@
 
 #include <FEXCore/Core/Context.h>
 #include <FEXCore/Core/HostFeatures.h>
+#include <FEXCore/Utils/CPUInfo.h>
 #include <FEXCore/fextl/fmt.h>
 
 #include <windows.h>
 
 #include "CPUFeatures.h"
 
 namespace {
+
+static void FillMIDRInformation(FEXCore::HostFeatures* Features, uint64_t MIDR) {
+  auto Cores = FEXCore::CPUInfo::CalculateNumberOfCPUs();
+  // Truncate to 32-bits, top 32-bits are all reserved in MIDR
+  Features->CPUMIDRs.resize(Cores, static_cast<uint32_t>(MIDR));
+}
+
 HKEY OpenProcessorKey(uint32_t Idx) {
   HKEY Out;
   auto Path = fextl::fmt::format("Hardware\\Description\\System\\CentralProcessor\\{}", Idx);
@@ -57,7 +65,9 @@ FEXCore::HostFeatures CPUFeatures::FetchHostFeatures(bool IsWine) {
 
   RegCloseKey(Key);
 
-  return FEX::FetchHostFeatures(Features, !IsWine, CTR, MIDR);
+  auto HostFeatures = FEX::FetchHostFeatures(Features, !IsWine, CTR, MIDR);
+  FillMIDRInformation(&HostFeatures, MIDR);
+  return HostFeatures;
 }
 
 CPUFeatures::CPUFeatures(FEXCore::Context::Context& CTX) {