s390: KVM guest: detect when running on kvm

This patch adds functionality to detect if the kernel runs under the KVM
hypervisor. A macro MACHINE_IS_KVM is exported for device drivers. This
allows drivers to skip device detection if the systems runs non-virtualized.
We also define a preferred console to avoid having the ttyS0, which is a line
mode only console.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 2f35133ebc18..a9d18aafa5f4 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -801,9 +801,13 @@ setup_arch(char **cmdline_p)
                "This machine has an IEEE fpu\n" :
                "This machine has no IEEE fpu\n");
 #else /* CONFIG_64BIT */
-        printk((MACHINE_IS_VM) ?
-               "We are running under VM (64 bit mode)\n" :
-               "We are running native (64 bit mode)\n");
+        if (MACHINE_IS_VM)
+                printk("We are running under VM (64 bit mode)\n");
+        else if (MACHINE_IS_KVM) {
+                printk("We are running under KVM (64 bit mode)\n");
+                add_preferred_console("ttyS", 1, NULL);
+        } else
+                printk("We are running native (64 bit mode)\n");
 #endif /* CONFIG_64BIT */
 
         /* Save unparsed command line copy for /proc/cmdline */