configs: Enable AVX2 for GPUFS+KVM

AVX is a requirement for some ROCm libraries, such as rocBLAS, which are
themselves requirements for libraries higher up the stack like PyTorch.
This patch sets the necessary CPUID bits in the GPUFS config to enable
AVX, AVX2, and various SSE features so that applications using these
libraries do not cause an illegal instruction trap.

Change-Id: Id22f543fb2a06b268271725a54075ee6a9a1f041

configs/example/gpufs/system/system.py

@@ -231,6 +231,42 @@ def makeGpuFSSystem(args):
         clock=args.ruby_clock, voltage_domain=system.voltage_domain
     )
 
+    # If we are using KVM cpu, enable AVX. AVX is used in some ROCm libraries
+    # such as rocBLAS which is used in higher level libraries like PyTorch.
+    use_avx = False
+    if ObjectList.is_kvm_cpu(TestCPUClass):
+        # AVX also requires CR4.osxsave to be 1. These must be set together
+        # of KVM will error out.
+        system.workload.enable_osxsave = 1
+        use_avx = True
+
+    # These values are taken from a real CPU and are further explained here:
+    # https://sandpile.org/x86/cpuid.htm#level_0000_000Dh
+    avx_extended_state = [
+        0x00000007,
+        0x00000340,
+        0x00000000,
+        0x00000340,
+        0x0000000F,
+        0x00000340,
+        0x00000000,
+        0x00000000,
+        0x00000100,
+        0x00000240,
+        0x00000000,
+        0x00000040,
+        0x00000000,
+        0x00000000,
+        0x00000000,
+        0x00000000,
+    ]
+
+    # This modifies the default value for ECX only (4th in this array).
+    # See: https://sandpile.org/x86/cpuid.htm#level_0000_0001h
+    # Enables AVX, OSXSAVE, XSAVE, POPCNT, SSE4.2, SSE4.1, CMPXCHG16B,
+    # and FMA.
+    avx_cpu_features = [0x00020F51, 0x00000805, 0xEFDBFBFF, 0x1C983209]
+
     for (i, cpu) in enumerate(system.cpu):
         # Break once we reach the shader "CPU"
         if i == args.num_cpus:
@@ -247,6 +283,9 @@ def makeGpuFSSystem(args):
 
         for j in range(len(system.cpu[i].isa)):
             system.cpu[i].isa[j].vendor_string = "AuthenticAMD"
+            if use_avx:
+                system.cpu[i].isa[j].ExtendedState = avx_extended_state
+                system.cpu[i].isa[j].FamilyModelStepping = avx_cpu_features
 
     if args.host_parallel:
         # To get the KVM CPUs to run on different host CPUs, specify a