[RFC/PATCH 14/15] guest: detect when running on kvm

Carsten Otte
2008-03-20T16:25:26Z

From: Christian Borntraeger <borntraeger@de.ibm.com>
From: Carsten Otte <cotte@de.ibm.com>

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>
---
arch/s390/Kconfig | 7 +++++++
arch/s390/kernel/early.c | 4 ++++
arch/s390/kernel/setup.c | 10 +++++++---
include/asm-s390/setup.h | 1 +
4 files changed, 19 insertions(+), 3 deletions(-)

Index: kvm/arch/s390/Kconfig
===================================================================
--- kvm.orig/arch/s390/Kconfig
+++ kvm/arch/s390/Kconfig
@@ -533,6 +533,13 @@ config ZFCPDUMP
Select this option if you want to build an zfcpdump enabled kernel.
Refer to <file:Documentation/s390/zfcpdump.txt> for more details on this.

+config S390_GUEST
+bool "s390 guest support (EXPERIMENTAL)"
+ depends on 64BIT && EXPERIMENTAL
+ select VIRTIO
+ select VIRTIO_RING
+ help
+ Select this option if you want to run the kernel under s390 linux
endmenu

source "net/Kconfig"
Index: kvm/arch/s390/kernel/early.c
===================================================================
--- kvm.orig/arch/s390/kernel/early.c
+++ kvm/arch/s390/kernel/early.c
@@ -143,6 +143,10 @@ static noinline __init void detect_machi
/* Running on a P/390 ? */
if (cpuinfo->cpu_id.machine == 0x7490)
machine_flags |= 4;
+
+ /* Running under KVM ? */
+ if (cpuinfo->cpu_id.version == 0xfe)
+ machine_flags |= 64;
}

#ifdef CONFIG_64BIT
Index: kvm/arch/s390/kernel/setup.c
===================================================================
--- kvm.orig/arch/s390/kernel/setup.c
+++ kvm/arch/s390/kernel/setup.c
@@ -793,9 +793,13 @@ 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 */
Index: kvm/include/asm-s390/setup.h
===================================================================
--- kvm.orig/include/asm-s390/setup.h
+++ kvm/include/asm-s390/setup.h
@@ -62,6 +62,7 @@ extern unsigned long machine_flags;
#define MACHINE_IS_VM (machine_flags & 1)
#define MACHINE_IS_P390 (machine_flags & 4)
#define MACHINE_HAS_MVPG (machine_flags & 16)
+#define MACHINE_IS_KVM (machine_flags & 64)
#define MACHINE_HAS_IDTE (machine_flags & 128)
#define MACHINE_HAS_DIAG9C (machine_flags & 256)