scripts/kvm/kvm_stat: Group arch specific data

Using global variables and multiple initialization functions for arch
specific data makes the code hard to read. By grouping them in the
Arch classes we encapsulate and initialize them in one place.
Signed-off-by: NJanosch Frank <frankja@linux.vnet.ibm.com>
Message-Id: <1452525484-32309-26-git-send-email-frankja@linux.vnet.ibm.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

scripts/kvm/kvm_stat

@@ -213,62 +213,72 @@ X86_EXIT_REASONS = {
     'svm': SVM_EXIT_REASONS,
 }
 
-SC_PERF_EVT_OPEN = None
-EXIT_REASONS = None
-
 IOCTL_NUMBERS = {
-    'SET_FILTER' : 0x40082406,
-    'ENABLE'     : 0x00002400,
-    'DISABLE'    : 0x00002401,
-    'RESET'      : 0x00002403,
+    'SET_FILTER':  0x40082406,
+    'ENABLE':      0x00002400,
+    'DISABLE':     0x00002401,
+    'RESET':       0x00002403,
 }
 
-def x86_init(flag):
-    global SC_PERF_EVT_OPEN
-    global EXIT_REASONS
-
-    SC_PERF_EVT_OPEN = 298
-    EXIT_REASONS = X86_EXIT_REASONS[flag]
-
-def s390_init():
-    global SC_PERF_EVT_OPEN
-
-    SC_PERF_EVT_OPEN = 331
-
-def ppc_init():
-    global SC_PERF_EVT_OPEN
-    global IOCTL_NUMBERS
-
-    SC_PERF_EVT_OPEN = 319
+class Arch(object):
+    """Class that encapsulates global architecture specific data like
+    syscall and ioctl numbers.
 
-    IOCTL_NUMBERS['ENABLE'] = 0x20002400
-    IOCTL_NUMBERS['DISABLE'] = 0x20002401
-    IOCTL_NUMBERS['SET_FILTER'] = 0x80002406 | (ctypes.sizeof(ctypes.c_char_p)
-                                                << 16)
+    """
+    @staticmethod
+    def get_arch():
+        machine = os.uname()[4]
+
+        if machine.startswith('ppc'):
+            return ArchPPC()
+        elif machine.startswith('aarch64'):
+            return ArchA64()
+        elif machine.startswith('s390'):
+            return ArchS390()
+        else:
+            # X86_64
+            for line in open('/proc/cpuinfo'):
+                if not line.startswith('flags'):
+                    continue
+
+                flags = line.split()
+                if 'vmx' in flags:
+                    return ArchX86(VMX_EXIT_REASONS)
+                if 'svm' in flags:
+                    return ArchX86(SVM_EXIT_REASONS)
+                return
+
+class ArchX86(Arch):
+    def __init__(self, exit_reasons):
+        self.sc_perf_evt_open = 298
+        self.ioctl_numbers = IOCTL_NUMBERS
+        self.exit_reasons = exit_reasons
+
+class ArchPPC(Arch):
+    def __init__(self):
+        self.sc_perf_evt_open = 319
+        self.ioctl_numbers = IOCTL_NUMBERS
+        self.ioctl_numbers['ENABLE'] = 0x20002400
+        self.ioctl_numbers['DISABLE'] = 0x20002401
 
-def aarch64_init():
-    global SC_PERF_EVT_OPEN
-    global EXIT_REASONS
+        # PPC comes in 32 and 64 bit and some generated ioctl
+        # numbers depend on the wordsize.
+        char_ptr_size = ctypes.sizeof(ctypes.c_char_p)
+        self.ioctl_numbers['SET_FILTER'] = 0x80002406 | char_ptr_size << 16
 
-    SC_PERF_EVT_OPEN = 241
-    EXIT_REASONS = AARCH64_EXIT_REASONS
+class ArchA64(Arch):
+    def __init__(self):
+        self.sc_perf_evt_open = 241
+        self.ioctl_numbers = IOCTL_NUMBERS
+        self.exit_reasons = AARCH64_EXIT_REASONS
 
-def detect_platform():
-    machine = os.uname()[4]
+class ArchS390(Arch):
+    def __init__(self):
+        self.sc_perf_evt_open = 331
+        self.ioctl_numbers = IOCTL_NUMBERS
+        self.exit_reasons = None
 
-    if machine.startswith('ppc'):
-        ppc_init()
-    elif machine.startswith('aarch64'):
-        aarch64_init()
-    elif machine.startswith('s390'):
-        s390_init()
-    else:
-        for line in file('/proc/cpuinfo').readlines():
-            if line.startswith('flags'):
-                for flag in line.split():
-                    if flag in X86_EXIT_REASONS:
-                        x86_init(flag)
-                        return
+ARCH = Arch.get_arch()
 
 
 def walkdir(path):
@@ -304,11 +314,10 @@ def get_online_cpus():
 
 
 def get_filters():
-    detect_platform()
     filters = {}
     filters['kvm_userspace_exit'] = ('reason', USERSPACE_EXIT_REASONS)
-    if EXIT_REASONS:
-        filters['kvm_exit'] = ('exit_reason', EXIT_REASONS)
+    if ARCH.exit_reasons:
+        filters['kvm_exit'] = ('exit_reason', ARCH.exit_reasons)
     return filters
 
 libc = ctypes.CDLL('libc.so.6', use_errno=True)
@@ -328,9 +337,9 @@ class perf_event_attr(ctypes.Structure):
                 ('bp_len', ctypes.c_uint64),
                 ]
 def perf_event_open(attr, pid, cpu, group_fd, flags):
-    return syscall(SC_PERF_EVT_OPEN, ctypes.pointer(attr), ctypes.c_int(pid),
-                   ctypes.c_int(cpu), ctypes.c_int(group_fd),
-                   ctypes.c_long(flags))
+    return syscall(ARCH.sc_perf_evt_open, ctypes.pointer(attr),
+                   ctypes.c_int(pid), ctypes.c_int(cpu),
+                   ctypes.c_int(group_fd), ctypes.c_long(flags))
 
 PERF_TYPE_TRACEPOINT = 2
 PERF_FORMAT_GROUP = 1 << 3
@@ -388,19 +397,19 @@ class Event(object):
                           'while calling sys_perf_event_open().')
 
         if trace_filter:
-            fcntl.ioctl(fd, IOCTL_NUMBERS['SET_FILTER'],
+            fcntl.ioctl(fd, ARCH.ioctl_numbers['SET_FILTER'],
                         trace_filter)
 
         self.fd = fd
 
     def enable(self):
-        fcntl.ioctl(self.fd, IOCTL_NUMBERS['ENABLE'], 0)
+        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['ENABLE'], 0)
 
     def disable(self):
-        fcntl.ioctl(self.fd, IOCTL_NUMBERS['DISABLE'], 0)
+        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['DISABLE'], 0)
 
     def reset(self):
-        fcntl.ioctl(self.fd, IOCTL_NUMBERS['RESET'], 0)
+        fcntl.ioctl(self.fd, ARCH.ioctl_numbers['RESET'], 0)
 
 class TracepointProvider(object):
     def __init__(self):