s390: use virtio_console for KVM on s390

This patch enables virtio_console as the default console on kvm for
s390. We currently use the same notify hack as lguest for early
console output. I will try to address this for lguest and s390 later.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

4 files changed, 34 insertions, 1 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index eb530b4128ba..2ed88122be93 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -565,6 +565,7 @@ bool "s390 guest support (EXPERIMENTAL)"
         depends on 64BIT && EXPERIMENTAL
         select VIRTIO
         select VIRTIO_RING
+        select VIRTIO_CONSOLE
         help
           Select this option if you want to run the kernel under s390 linux
 endmenu
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index b358e18273b0..62122bad1e33 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -54,6 +54,7 @@
 #include <asm/sections.h>
 #include <asm/ebcdic.h>
 #include <asm/compat.h>
+#include <asm/kvm_virtio.h>
 
 long psw_kernel_bits    = (PSW_BASE_BITS | PSW_MASK_DAT | PSW_ASC_PRIMARY |
                            PSW_MASK_MCHECK | PSW_DEFAULT_KEY);
@@ -766,7 +767,8 @@ setup_arch(char **cmdline_p)
                 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);
+                add_preferred_console("hvc", 0, NULL);
+                s390_virtio_console_init();
         } else
                 printk("We are running native (64 bit mode)\n");
 #endif /* CONFIG_64BIT */
diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
index 5ab34340919b..d41f234bb2c2 100644
--- a/drivers/s390/kvm/kvm_virtio.c
+++ b/drivers/s390/kvm/kvm_virtio.c
@@ -15,6 +15,7 @@
 #include <linux/err.h>
 #include <linux/virtio.h>
 #include <linux/virtio_config.h>
+#include <linux/virtio_console.h>
 #include <linux/interrupt.h>
 #include <linux/virtio_ring.h>
 #include <linux/pfn.h>
@@ -333,6 +334,25 @@ static int __init kvm_devices_init(void)
         return 0;
 }
 
+/* code for early console output with virtio_console */
+static __init int early_put_chars(u32 vtermno, const char *buf, int count)
+{
+        char scratch[17];
+        unsigned int len = count;
+
+        if (len > sizeof(scratch) - 1)
+                len = sizeof(scratch) - 1;
+        scratch[len] = '\0';
+        memcpy(scratch, buf, len);
+        kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, __pa(scratch));
+        return len;
+}
+
+void s390_virtio_console_init(void)
+{
+        virtio_cons_early_init(early_put_chars);
+}
+
 /*
  * We do this after core stuff, but before the drivers.
  */
diff --git a/include/asm-s390/kvm_virtio.h b/include/asm-s390/kvm_virtio.h
index 5c871a990c29..146100224def 100644
--- a/include/asm-s390/kvm_virtio.h
+++ b/include/asm-s390/kvm_virtio.h
@@ -50,4 +50,14 @@ struct kvm_vqconfig {
 #define KVM_S390_VIRTIO_RESET           1
 #define KVM_S390_VIRTIO_SET_STATUS      2
 
+#ifdef __KERNEL__
+/* early virtio console setup */
+#ifdef CONFIG_VIRTIO_CONSOLE
+extern void s390_virtio_console_init(void);
+#else
+static inline void s390_virtio_console_init(void)
+{
+}
+#endif /* CONFIG_VIRTIO_CONSOLE */
+#endif /* __KERNEL__ */
 #endif