build: Don't test for KVM xsave support on ARM

The current build tests for KVM unconditionally check for xsave
support. This obviously never works on ARM since xsave is
x86-specific. This changeset refactors the build tests probing for KVM
support and moves the xsave test to an x86-specific section of
is_isa_kvm_compatible().

diff --git a/SConstruct b/SConstruct
index c51c7b28cdee19996c608102a5fb8269eafaa6f6..2d61aa0f2e21f83725c1e4243f94283a923383ee 100755 (executable)
--- a/SConstruct
+++ b/SConstruct
@@ -1,6 +1,6 @@
 # -*- mode:python -*-
 
-# Copyright (c) 2013 ARM Limited
+# Copyright (c) 2013, 2015 ARM Limited
 # All rights reserved.
 #
 # The license below extends only to copyright in the software and shall
@@ -1022,18 +1022,19 @@ if not have_fenv:
 # we rely on exists since version 2.6.36 of the kernel, but somehow
 # the KVM_API_VERSION does not reflect the change. We test for one of
 # the types as a fall back.
-have_kvm = conf.CheckHeader('linux/kvm.h', '<>') and \
-    conf.CheckTypeSize('struct kvm_xsave', '#include <linux/kvm.h>') != 0
+have_kvm = conf.CheckHeader('linux/kvm.h', '<>')
 if not have_kvm:
     print "Info: Compatible header file <linux/kvm.h> not found, " \
         "disabling KVM support."
 
+# x86 needs support for xsave. We test for the structure here since we
+# won't be able to run new tests by the time we know which ISA we're
+# targeting.
+have_kvm_xsave = conf.CheckTypeSize('struct kvm_xsave',
+                                    '#include <linux/kvm.h>') != 0
+
 # Check if the requested target ISA is compatible with the host
 def is_isa_kvm_compatible(isa):
-    isa_comp_table = {
-        "arm" : ( "armv7l" ),
-        "x86" : ( "x86_64" ),
-        }
     try:
         import platform
         host_isa = platform.machine()
@@ -1041,7 +1042,24 @@ def is_isa_kvm_compatible(isa):
         print "Warning: Failed to determine host ISA."
         return False
 
-    return host_isa in isa_comp_table.get(isa, [])
+    if not have_posix_timers:
+        print "Warning: Can not enable KVM, host seems to lack support " \
+            "for POSIX timers"
+        return False
+
+    if isa == "arm":
+        return host_isa == "armv7l"
+    elif isa == "x86":
+        if host_isa != "x86_64":
+            return False
+
+        if not have_kvm_xsave:
+            print "KVM on x86 requires xsave support in kernel headers."
+            return False
+
+        return True
+    else:
+        return False
 
 
 # Check if the exclude_host attribute is available. We want this to
@@ -1357,10 +1375,6 @@ for variant_path in variant_paths:
         if not have_kvm:
             print "Warning: Can not enable KVM, host seems to lack KVM support"
             env['USE_KVM'] = False
-        elif not have_posix_timers:
-            print "Warning: Can not enable KVM, host seems to lack support " \
-                "for POSIX timers"
-            env['USE_KVM'] = False
         elif not is_isa_kvm_compatible(env['TARGET_ISA']):
             print "Info: KVM support disabled due to unsupported host and " \
                 "target ISA combination"