X86: Add a check to catch Xen emulation of Hyper-V
authorK. Y. Srinivasan <kys@microsoft.com>
Mon, 4 Feb 2013 01:22:38 +0000 (17:22 -0800)
committerH. Peter Anvin <hpa@linux.intel.com>
Wed, 13 Feb 2013 00:27:03 +0000 (16:27 -0800)
Xen emulates Hyper-V to host enlightened Windows. Looks like this
emulation may be turned on by default even for Linux guests. Check and
fail Hyper-V detection if we are on Xen.

[ hpa: the problem here is that Xen doesn't emulate Hyper-V well
  enough, and if the Xen support isn't compiled in, we end up stubling
  over the Hyper-V emulation and try to activate it -- and it fails. ]

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Link: http://lkml.kernel.org/r/1359940959-32168-2-git-send-email-kys@microsoft.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
arch/x86/kernel/cpu/mshyperv.c

index 646d192b18a216ff6305e0aea0046968a5b39b7b..4dab317f79b923b616a57b96bad52c1298b61562 100644 (file)
@@ -30,6 +30,13 @@ static bool __init ms_hyperv_platform(void)
        if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
                return false;
 
+       /*
+        * Xen emulates Hyper-V to support enlightened Windows.
+        * Check to see first if we are on a Xen Hypervisor.
+        */
+       if (xen_cpuid_base())
+               return false;
+
        cpuid(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS,
              &eax, &hyp_signature[0], &hyp_signature[1], &hyp_signature[2]);