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>

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9a742ce..8f5f021 100644 (file)
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -520,6 +520,13 @@ 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"

diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index 540a67f..68ec408 100644 (file)
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -144,6 +144,10 @@ static noinline __init void detect_machine_type(void)
        /* 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

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 2f35133..a9d18aa 100644 (file)
--- 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 */

diff --git a/include/asm-s390/setup.h b/include/asm-s390/setup.h
index a76a6b8..aaf4b51 100644 (file)
--- a/include/asm-s390/setup.h
+++ b/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)