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Subject[RFC 3/3] s390: use virtio_console for KVM on s390
Date
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>
---
arch/s390/Kconfig | 1 +
arch/s390/kernel/setup.c | 4 +++-
drivers/s390/kvm/kvm_virtio.c | 20 ++++++++++++++++++++
include/asm-s390/kvm_virtio.h | 10 ++++++++++
4 files changed, 34 insertions(+), 1 deletion(-)
Index: kvm/arch/s390/Kconfig
===================================================================
--- kvm.orig/arch/s390/Kconfig
+++ kvm/arch/s390/Kconfig
@@ -540,6 +540,7 @@ 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
Index: kvm/arch/s390/kernel/setup.c
===================================================================
--- kvm.orig/arch/s390/kernel/setup.c
+++ kvm/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);
@@ -799,7 +800,8 @@ 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 */
Index: kvm/drivers/s390/kvm/kvm_virtio.c
===================================================================
--- kvm.orig/drivers/s390/kvm/kvm_virtio.c
+++ kvm/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>
@@ -338,6 +339,25 @@ 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.
*/
Index: kvm/include/asm-s390/kvm_virtio.h
===================================================================
--- kvm.orig/include/asm-s390/kvm_virtio.h
+++ kvm/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

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