cpu-gather: Move msr decoding to new script

Fixes the leaking file descriptors. Does not silently ignore errors
(e.g. permission denied on /dev/cpu/0/msr if run as non-root) and
always attempt to read from /dev/kvm if /dev/cpu/0/msr failed.

'gather_msr()' returns a dictionary of values, as a later patch will
add more registers to be interrogated.

Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

tests/cputestdata/cpu-gather.py

@@ -1,8 +1,11 @@
 #!/usr/bin/env python3
 
 import argparse
+import fcntl
 import os
+import struct
 import subprocess
+import sys
 
 
 def gather_name(args):
@@ -38,6 +41,31 @@ def gather_cpuid_leaves(args):
         yield line.strip()
 
 
+def gather_msr():
+    IA32_ARCH_CAPABILITIES_MSR = 0x10a
+    KVM_GET_MSRS = 0xc008ae88
+
+    try:
+        with open("/dev/cpu/0/msr", "rb") as f:
+            f.seek(IA32_ARCH_CAPABILITIES_MSR)
+            buf = f.read(8)
+            msr = struct.unpack("=Q", buf)[0]
+            return "", {IA32_ARCH_CAPABILITIES_MSR: msr}
+    except IOError as e:
+        print("Warning: {}".format(e), file=sys.stderr)
+
+    try:
+        bufIn = struct.pack("=LLLLQ", 1, 0, IA32_ARCH_CAPABILITIES_MSR, 0, 0)
+        with open("/dev/kvm", "rb") as f:
+            bufOut = fcntl.ioctl(f, KVM_GET_MSRS, bufIn)
+            msr = struct.unpack("=LLLLQ", bufOut)[4]
+            return " via KVM", {IA32_ARCH_CAPABILITIES_MSR: msr}
+    except IOError as e:
+        print("Warning: {}".format(e), file=sys.stderr)
+
+    return None, {}
+
+
 def main():
     parser = argparse.ArgumentParser(description="Gather cpu test data")
     parser.add_argument(
@@ -61,6 +89,12 @@ def main():
         print("   {}".format(leave))
     print()
 
+    via, msr = gather_msr()
+    if via is not None:
+        print("MSR{}:".format(via))
+        for key, value in sorted(msr.items()):
+            print("   0x{:x}: 0x{:016x}\n".format(int(key), value))
+
     print(end="", flush=True)
     os.environ["CPU_GATHER_PY"] = "true"
     subprocess.check_call("./cpu-gather.sh")

tests/cputestdata/cpu-gather.sh

@@ -5,46 +5,6 @@ if [ -z "${CPU_GATHER_PY}" ]; then
     exit 1
 fi
 
-python3 <<EOF
-from struct import pack, unpack
-from fcntl import ioctl
-import sys, errno
-
-IA32_ARCH_CAPABILITIES_MSR = 0x10a
-KVM_GET_MSRS = 0xc008ae88
-
-def print_msr(msr, via=None):
-    if via is None:
-        print("MSR:")
-    else:
-        print("MSR via %s:" % via)
-    print("   0x%x: 0x%016x" % (IA32_ARCH_CAPABILITIES_MSR, msr))
-    print()
-
-try:
-    fd = open("/dev/cpu/0/msr", "rb")
-    fd.seek(IA32_ARCH_CAPABILITIES_MSR)
-    buf = fd.read(8)
-    msr = unpack("=Q", buf)[0]
-
-    print_msr(msr)
-    sys.exit(0)
-except IOError as e:
-    # The MSR is not supported on the host
-    if e.errno == errno.EIO:
-        sys.exit(0)
-
-try:
-    fd = open("/dev/kvm", "r")
-    bufIn = pack("=LLLLQ", 1, 0, IA32_ARCH_CAPABILITIES_MSR, 0, 0)
-    bufOut = ioctl(fd, KVM_GET_MSRS, bufIn)
-    msr = unpack("=LLLLQ", bufOut)[4]
-
-    print_msr(msr, via="KVM")
-except IOError as e:
-    pass
-EOF
-
 qemu=qemu-system-x86_64
 for cmd in /usr/bin/$qemu /usr/bin/qemu-kvm /usr/libexec/qemu-kvm; do
     if [[ -x $cmd ]]; then