[PATCH v3 3/3] tile: enable VIRTIO support for KVM

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This change enables support for a virtio-based console,
network support, and block driver support.

We remove some debug code in relocate_kernel_64.S that made raw
calls to the hv_console_putc Tilera hypervisor API, since everything
now should funnel through the early_hv_write() API.

Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
---
 arch/tile/Kconfig                       |   3 +
 arch/tile/include/asm/kvm_para.h        |  20 ++
 arch/tile/include/asm/kvm_virtio.h      |  26 ++
 arch/tile/include/uapi/asm/Kbuild       |   1 +
 arch/tile/include/uapi/asm/kvm.h        |   5 +
 arch/tile/include/uapi/asm/kvm_virtio.h |  60 +++++
 arch/tile/kernel/Makefile               |   1 +
 arch/tile/kernel/early_printk.c         |  16 ++
 arch/tile/kernel/hvglue.S               |   1 +
 arch/tile/kernel/kvm_virtio.c           | 430 ++++++++++++++++++++++++++++++++
 arch/tile/kernel/relocate_kernel_64.S   |   9 +-
 11 files changed, 570 insertions(+), 2 deletions(-)
 create mode 100644 arch/tile/include/asm/kvm_para.h
 create mode 100644 arch/tile/include/asm/kvm_virtio.h
 create mode 100644 arch/tile/include/uapi/asm/kvm_virtio.h
 create mode 100644 arch/tile/kernel/kvm_virtio.c

diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index e89aae8..4e8524b 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -370,6 +370,9 @@ config KVM_GUEST
 	bool "Build kernel as guest for KVM"
 	default n
 	depends on TILEGX
+	select VIRTIO
+	select VIRTIO_RING
+	select VIRTIO_CONSOLE
 	---help---
 	  This will build a kernel that runs at a lower protection level
 	  than the default kernel and is suitable to run under KVM.
diff --git a/arch/tile/include/asm/kvm_para.h b/arch/tile/include/asm/kvm_para.h
new file mode 100644
index 0000000..c8c31d5
--- /dev/null
+++ b/arch/tile/include/asm/kvm_para.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright 2013 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+#ifndef _ASM_TILE_KVM_PARA_H
+#define _ASM_TILE_KVM_PARA_H
+
+#include <uapi/asm/kvm_para.h>
+
+int hcall_virtio(unsigned long instrument, unsigned long mem);
+#endif /* _ASM_TILE_KVM_PARA_H */
diff --git a/arch/tile/include/asm/kvm_virtio.h b/arch/tile/include/asm/kvm_virtio.h
new file mode 100644
index 0000000..8faa959
--- /dev/null
+++ b/arch/tile/include/asm/kvm_virtio.h
@@ -0,0 +1,26 @@
+/*
+ * Copyright 2013 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+#ifndef _ASM_TILE_KVM_VIRTIO_H
+#define _ASM_TILE_KVM_VIRTIO_H
+
+#include <uapi/asm/kvm_virtio.h>
+
+
+struct kvm_device {
+	struct virtio_device vdev;
+	struct kvm_device_desc *desc;
+	unsigned long desc_pa;
+};
+
+#endif /* _ASM_TILE_KVM_VIRTIO_H */
diff --git a/arch/tile/include/uapi/asm/Kbuild b/arch/tile/include/uapi/asm/Kbuild
index 89022a5..f07cc24 100644
--- a/arch/tile/include/uapi/asm/Kbuild
+++ b/arch/tile/include/uapi/asm/Kbuild
@@ -8,6 +8,7 @@ header-y += cachectl.h
 header-y += hardwall.h
 header-y += kvm.h
 header-y += kvm_para.h
+header-y += kvm_virtio.h
 header-y += mman.h
 header-y += ptrace.h
 header-y += setup.h
diff --git a/arch/tile/include/uapi/asm/kvm.h b/arch/tile/include/uapi/asm/kvm.h
index aa7b97f..4346520 100644
--- a/arch/tile/include/uapi/asm/kvm.h
+++ b/arch/tile/include/uapi/asm/kvm.h
@@ -149,6 +149,9 @@
  */
 #define KVM_OTHER_HCALL                  128
 
+/* Hypercall index for virtio. */
+#define KVM_HCALL_virtio                 128
+
 /* One greater than the maximum hypercall number. */
 #define KVM_NUM_HCALLS                   256
 
@@ -256,6 +259,8 @@ struct kvm_sync_regs {
 	KVM_EMULATE(get_ipi_pte) \
 	KVM_EMULATE(set_pte_super_shift) \
 	KVM_EMULATE(set_speed) \
+	/* For others */ \
+	USER_HCALL(virtio)
 
 #endif
 
diff --git a/arch/tile/include/uapi/asm/kvm_virtio.h b/arch/tile/include/uapi/asm/kvm_virtio.h
new file mode 100644
index 0000000..d94f535
--- /dev/null
+++ b/arch/tile/include/uapi/asm/kvm_virtio.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2013 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+
+#ifndef _UAPI_ASM_TILE_KVM_VIRTIO_H
+#define _UAPI_ASM_TILE_KVM_VIRTIO_H
+
+#include <linux/types.h>
+
+#define KVM_VIRTIO_UNKNOWN	0
+#define KVM_VIRTIO_NOTIFY	1
+#define KVM_VIRTIO_RESET	2
+#define KVM_VIRTIO_SET_STATUS	3
+
+struct kvm_device_desc {
+	/* The device type: console, network, disk etc.  Type 0 terminates. */
+	__u8 type;
+	/* The number of virtqueues (first in config array) */
+	__u8 num_vq;
+	/*
+	 * The number of bytes of feature bits.  Multiply by 2: one for host
+	 * features and one for Guest acknowledgements.
+	 */
+	__u8 feature_len;
+	/* The number of bytes of the config array after virtqueues. */
+	__u8 config_len;
+	/* A status byte, written by the Guest. */
+	__u8 status;
+	__u64 config[0];
+};
+
+struct kvm_vqinfo {
+	/* Pointer to the information contained in the device config. */
+	struct kvm_vqconfig *config;
+	/* The address where we mapped the virtio ring, so we can unmap it. */
+	void *pages;
+};
+
+struct kvm_vqconfig {
+	/* The physical address of the virtio ring */
+	__u64 pa;
+	/* The number of entries in the virtio_ring */
+	__u64 num;
+	/* The interrupt we get when something happens. Set by the guest. */
+	__u32 irq;
+
+};
+
+
+#endif /* _UAPI_ASM_TILE_KVM_VIRTIO_H */
diff --git a/arch/tile/kernel/Makefile b/arch/tile/kernel/Makefile
index b7c8b5e..b638d3e 100644
--- a/arch/tile/kernel/Makefile
+++ b/arch/tile/kernel/Makefile
@@ -29,5 +29,6 @@ obj-$(CONFIG_TILE_USB)		+= usb.o
 obj-$(CONFIG_TILE_HVGLUE_TRACE)	+= hvglue_trace.o
 obj-$(CONFIG_FUNCTION_TRACER)	+= ftrace.o mcount_64.o
 obj-$(CONFIG_KPROBES)		+= kprobes.o
+obj-$(CONFIG_KVM_GUEST)		+= kvm_virtio.o
 
 obj-y				+= vdso/
diff --git a/arch/tile/kernel/early_printk.c b/arch/tile/kernel/early_printk.c
index b608e00..53f2be4 100644
--- a/arch/tile/kernel/early_printk.c
+++ b/arch/tile/kernel/early_printk.c
@@ -18,11 +18,26 @@
 #include <linux/string.h>
 #include <linux/irqflags.h>
 #include <linux/printk.h>
+#ifdef CONFIG_KVM_GUEST
+#include <linux/virtio_console.h>
+#include <linux/kvm_para.h>
+#include <asm/kvm_virtio.h>
+#endif
 #include <asm/setup.h>
 #include <hv/hypervisor.h>
 
 static void early_hv_write(struct console *con, const char *s, unsigned n)
 {
+#ifdef CONFIG_KVM_GUEST
+	char buf[512];
+
+	if (n > sizeof(buf) - 1)
+		n = sizeof(buf) - 1;
+	memcpy(buf, s, n);
+	buf[n] = '\0';
+
+	hcall_virtio(KVM_VIRTIO_NOTIFY, __pa(buf));
+#else
 	tile_console_write(s, n);
 
 	/*
@@ -32,6 +47,7 @@ static void early_hv_write(struct console *con, const char *s, unsigned n)
 	 */
 	if (n && s[n-1] == '\n')
 		tile_console_write("\r", 1);
+#endif
 }
 
 static struct console early_hv_console = {
diff --git a/arch/tile/kernel/hvglue.S b/arch/tile/kernel/hvglue.S
index dc5b417..2914a9e 100644
--- a/arch/tile/kernel/hvglue.S
+++ b/arch/tile/kernel/hvglue.S
@@ -77,4 +77,5 @@ gensym hv_install_guest_context, 0x7a0, 32
 gensym hv_inquire_guest_context, 0x7c0, 32
 gensym hv_console_set_ipi, 0x7e0, 32
 gensym hv_glue_internals, 0x800, 2048
+gensym hcall_virtio, 0x1000, 32
 gensym hv_hcall_internals, 0x1020, 28640
diff --git a/arch/tile/kernel/kvm_virtio.c b/arch/tile/kernel/kvm_virtio.c
new file mode 100644
index 0000000..c6b6c6a
--- /dev/null
+++ b/arch/tile/kernel/kvm_virtio.c
@@ -0,0 +1,430 @@
+/*
+ * Copyright 2013 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+
+/* Referred lguest & s390 implemenation */
+/*
+ * kvm_virtio.c - virtio for kvm on s390
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License (version 2 only)
+ * as published by the Free Software Foundation.
+ *
+ *    Author(s): Christian Borntraeger <borntraeger@xxxxxxxxxx>
+ */
+
+#include <linux/bootmem.h>
+#include <linux/io.h>
+#include <linux/vmalloc.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/export.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_console.h>
+#include <linux/virtio_ring.h>
+#include <linux/virtio_pci.h>
+
+#include <linux/kvm_para.h>
+#include <asm/kvm_virtio.h>
+
+static void *kvm_devices;
+
+/*
+ * TODO: We actually does not use PCI virtio here. We use this
+ * because qemu: virtqueue_init() uses VIRTIO_PCI_VRING_ALIGN.
+ * Maybe we should change them to generic definitions in both qemu & Linux.
+ * Besides, Let's check whether the alignment value (4096, i.e. default
+ * x86 page size) affects performance later.
+ */
+#define KVM_TILE_VIRTIO_RING_ALIGN	VIRTIO_PCI_VRING_ALIGN
+#define to_kvmdev(vd)	container_of(vd, struct kvm_device, vdev)
+
+/*
+ * memory layout: (Total: PAGE_SIZE)
+ * <device 0>
+ * - kvm device descriptor
+ *        struct kvm_device_desc
+ * - vqueue configuration (totally desc->num_vq)
+ *        struct kvm_vqconfig
+ *        ......
+ *        struct kvm_vqconfig
+ * - feature bits (size: desc->feature_len * 2)
+ * - config space (size: desc->config_len)
+ * <device 1>
+ * ......
+ */
+static struct kvm_vqconfig *kvm_vq_config(const struct kvm_device_desc *desc)
+{
+	return (struct kvm_vqconfig *)(desc + 1);
+}
+
+static u8 *kvm_vq_features(const struct kvm_device_desc *desc)
+{
+	return (u8 *)(kvm_vq_config(desc) + desc->num_vq);
+}
+
+static u8 *kvm_vq_configspace(const struct kvm_device_desc *desc)
+{
+	return kvm_vq_features(desc) + desc->feature_len * 2;
+}
+
+/*
+ * The total size of the config page used by this device (incl. desc)
+ */
+static unsigned desc_size(const struct kvm_device_desc *desc)
+{
+	return sizeof(*desc)
+		+ desc->num_vq * sizeof(struct kvm_vqconfig)
+		+ desc->feature_len * 2
+		+ desc->config_len;
+}
+
+/* This gets the device's feature bits. */
+static u32 kvm_get_features(struct virtio_device *vdev)
+{
+	unsigned int i;
+	u32 features = 0;
+	struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
+	u8 *in_features = kvm_vq_features(desc);
+
+	for (i = 0; i < min(desc->feature_len * 8, 32); i++)
+		if (in_features[i / 8] & (1 << (i % 8)))
+			features |= (1 << i);
+	return features;
+}
+
+static void kvm_finalize_features(struct virtio_device *vdev)
+{
+	unsigned int i, bits;
+	struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
+	/* Second half of bitmap is features we accept. */
+	u8 *out_features = kvm_vq_features(desc) + desc->feature_len;
+
+	/* Give virtio_ring a chance to accept features. */
+	vring_transport_features(vdev);
+
+	memset(out_features, 0, desc->feature_len);
+	bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
+	for (i = 0; i < bits; i++) {
+		if (test_bit(i, vdev->features))
+			out_features[i / 8] |= (1 << (i % 8));
+	}
+}
+
+/*
+ * Reading and writing elements in config space
+ */
+static void kvm_get(struct virtio_device *vdev, unsigned int offset,
+		   void *buf, unsigned len)
+{
+	struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
+
+	BUG_ON(offset + len > desc->config_len);
+	memcpy(buf, kvm_vq_configspace(desc) + offset, len);
+}
+
+static void kvm_set(struct virtio_device *vdev, unsigned int offset,
+		   const void *buf, unsigned len)
+{
+	struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
+
+	BUG_ON(offset + len > desc->config_len);
+	memcpy(kvm_vq_configspace(desc) + offset, buf, len);
+}
+
+/*
+ * The operations to get and set the status word just access
+ * the status field of the device descriptor. set_status will also
+ * make a hypercall to the host, to tell about status changes
+ */
+static u8 kvm_get_status(struct virtio_device *vdev)
+{
+	return to_kvmdev(vdev)->desc->status;
+}
+
+static void kvm_set_status(struct virtio_device *vdev, u8 status)
+{
+	BUG_ON(!status);
+	to_kvmdev(vdev)->desc->status = status;
+	hcall_virtio(KVM_VIRTIO_SET_STATUS, to_kvmdev(vdev)->desc_pa);
+}
+
+/*
+ * To reset the device, we use the KVM_VIRTIO_RESET hypercall, using the
+ * descriptor address. The Host will zero the status and all the
+ * features.
+ */
+static void kvm_reset(struct virtio_device *vdev)
+{
+	hcall_virtio(KVM_VIRTIO_RESET, to_kvmdev(vdev)->desc_pa);
+}
+
+/*
+ * When the virtio_ring code wants to notify the Host, it calls us here and we
+ * make a hypercall.  We hand the address  of the virtqueue so the Host
+ * knows which virtqueue we're talking about.
+ */
+static void kvm_notify(struct virtqueue *vq)
+{
+	struct kvm_vqinfo *vqi = vq->priv;
+
+	hcall_virtio(KVM_VIRTIO_NOTIFY, vqi->config->pa);
+}
+
+/*
+ * Must set some caching mode to keep set_pte() happy.
+ * It doesn't matter what we choose, because the PFN
+ * is illegal, so we're going to take a page fault anyway.
+ */
+static inline pgprot_t io_prot(void)
+{
+	return hv_pte_set_mode(PAGE_KERNEL, HV_PTE_MODE_UNCACHED);
+}
+
+/*
+ * This routine finds the first virtqueue described in the configuration of
+ * this device and sets it up.
+ */
+static struct virtqueue *kvm_find_vq(struct virtio_device *vdev,
+				     unsigned index,
+				     void (*callback)(struct virtqueue *vq),
+				     const char *name)
+{
+	struct kvm_device *kdev = to_kvmdev(vdev);
+	struct kvm_vqinfo *vqi;
+	struct kvm_vqconfig *config;
+	struct virtqueue *vq;
+	long irq;
+	int err = -EINVAL;
+
+	if (index >= kdev->desc->num_vq)
+		return ERR_PTR(-ENOENT);
+
+	vqi = kzalloc(sizeof(*vqi), GFP_KERNEL);
+	if (!vqi)
+		return ERR_PTR(-ENOMEM);
+
+	config = kvm_vq_config(kdev->desc)+index;
+
+	vqi->config = config;
+	vqi->pages = generic_remap_prot(config->pa,
+				vring_size(config->num,
+					KVM_TILE_VIRTIO_RING_ALIGN),
+					0, io_prot());
+	if (!vqi->pages) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	vq = vring_new_virtqueue(index, config->num, KVM_TILE_VIRTIO_RING_ALIGN,
+				 vdev, 0, vqi->pages,
+				 kvm_notify, callback, name);
+	if (!vq) {
+		err = -ENOMEM;
+		goto unmap;
+	}
+
+	/*
+	 * Trigger the IPI interrupt in SW way.
+	 * TODO: We do not need to create one irq for each vq. A bit wasteful.
+	 */
+	irq = create_irq();
+	if (irq < 0) {
+		err = -ENXIO;
+		goto del_virtqueue;
+	}
+
+	tile_irq_activate(irq, TILE_IRQ_SW_CLEAR);
+
+	if (request_irq(irq, vring_interrupt, 0, dev_name(&vdev->dev), vq)) {
+		err = -ENXIO;
+		destroy_irq(irq);
+		goto del_virtqueue;
+	}
+
+	config->irq = irq;
+
+	vq->priv = vqi;
+	return vq;
+
+del_virtqueue:
+	vring_del_virtqueue(vq);
+unmap:
+	vunmap(vqi->pages);
+out:
+	return ERR_PTR(err);
+}
+
+static void kvm_del_vq(struct virtqueue *vq)
+{
+	struct kvm_vqinfo *vqi = vq->priv;
+
+	vring_del_virtqueue(vq);
+	vunmap(vqi->pages);
+	kfree(vqi);
+}
+
+static void kvm_del_vqs(struct virtio_device *vdev)
+{
+	struct virtqueue *vq, *n;
+
+	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
+		kvm_del_vq(vq);
+}
+
+static int kvm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
+			struct virtqueue *vqs[],
+			vq_callback_t *callbacks[],
+			const char *names[])
+{
+	struct kvm_device *kdev = to_kvmdev(vdev);
+	int i;
+
+	/* We must have this many virtqueues. */
+	if (nvqs > kdev->desc->num_vq)
+		return -ENOENT;
+
+	for (i = 0; i < nvqs; ++i) {
+		vqs[i] = kvm_find_vq(vdev, i, callbacks[i], names[i]);
+		if (IS_ERR(vqs[i]))
+			goto error;
+	}
+	return 0;
+
+error:
+	kvm_del_vqs(vdev);
+	return PTR_ERR(vqs[i]);
+}
+
+/*
+ * The config ops structure as defined by virtio config
+ */
+static struct virtio_config_ops kvm_vq_config_ops = {
+	.get_features = kvm_get_features,
+	.finalize_features = kvm_finalize_features,
+	.get = kvm_get,
+	.set = kvm_set,
+	.get_status = kvm_get_status,
+	.set_status = kvm_set_status,
+	.reset = kvm_reset,
+	.find_vqs = kvm_find_vqs,
+	.del_vqs = kvm_del_vqs,
+};
+
+/*
+ * The root device for the kvm virtio devices.
+ * This makes them appear as /sys/devices/kvm_tile/0,1,2 not /sys/devices/0,1,2.
+ */
+static struct device *kvm_root;
+
+/*
+ * adds a new device and register it with virtio
+ * appropriate drivers are loaded by the device model
+ */
+static void add_kvm_device(struct kvm_device_desc *d, unsigned int offset)
+{
+	struct kvm_device *kdev;
+
+	kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
+	if (!kdev) {
+		pr_emerg("Cannot allocate kvm dev %u type %u\n",
+			 offset, d->type);
+		return;
+	}
+
+	kdev->vdev.dev.parent = kvm_root;
+	kdev->vdev.id.device = d->type;
+	kdev->vdev.config = &kvm_vq_config_ops;
+	kdev->desc = d;
+	kdev->desc_pa = PFN_PHYS(max_pfn) + offset;
+
+	if (register_virtio_device(&kdev->vdev) != 0) {
+		pr_err("Failed to register kvm device %u type %u\n",
+		       offset, d->type);
+		kfree(kdev);
+	}
+}
+
+/*
+ * scan_devices() simply iterates through the device page.
+ * The type 0 is reserved to mean "end of devices".
+ */
+static void scan_devices(void)
+{
+	unsigned int i;
+	struct kvm_device_desc *d;
+
+	for (i = 0; i < PAGE_SIZE; i += desc_size(d)) {
+		d = kvm_devices + i;
+
+		if (d->type == 0)
+			break;
+
+		add_kvm_device(d, i);
+	}
+}
+
+/*
+ * Init function for virtio.
+ * devices are in a single page above the top of "normal" mem.
+ */
+static int __init kvm_devices_init(void)
+{
+	int rc = -ENOMEM;
+
+	kvm_root = root_device_register("kvm_tile");
+	if (IS_ERR(kvm_root)) {
+		rc = PTR_ERR(kvm_root);
+		pr_err("Could not register kvm_tile root device");
+		return rc;
+	}
+
+	kvm_devices = generic_remap_prot(PFN_PHYS(max_pfn), PAGE_SIZE,
+					 0, io_prot());
+	if (!kvm_devices) {
+		kvm_devices = NULL;
+		root_device_unregister(kvm_root);
+		return rc;
+	}
+
+	scan_devices();
+	return 0;
+}
+
+/* code for early console output with virtio_console */
+static __init int early_put_chars(u32 vtermno, const char *buf, int len)
+{
+	char scratch[512];
+
+	if (len > sizeof(scratch) - 1)
+		len = sizeof(scratch) - 1;
+	scratch[len] = '\0';
+	memcpy(scratch, buf, len);
+	hcall_virtio(KVM_VIRTIO_NOTIFY, __pa(scratch));
+
+	return len;
+}
+
+static int __init tile_virtio_console_init(void)
+{
+	return virtio_cons_early_init(early_put_chars);
+}
+console_initcall(tile_virtio_console_init);
+
+/*
+ * We do this after core stuff, but before the drivers.
+ */
+postcore_initcall(kvm_devices_init);
diff --git a/arch/tile/kernel/relocate_kernel_64.S b/arch/tile/kernel/relocate_kernel_64.S
index 1c09a4f..02bc446 100644
--- a/arch/tile/kernel/relocate_kernel_64.S
+++ b/arch/tile/kernel/relocate_kernel_64.S
@@ -34,11 +34,11 @@ STD_ENTRY(relocate_new_kernel)
 	addi	sp, sp, -8
 	/* we now have a stack (whether we need one or not) */
 
+#ifdef RELOCATE_NEW_KERNEL_VERBOSE
 	moveli	r40, hw2_last(hv_console_putc)
 	shl16insli r40, r40, hw1(hv_console_putc)
 	shl16insli r40, r40, hw0(hv_console_putc)
 
-#ifdef RELOCATE_NEW_KERNEL_VERBOSE
 	moveli	r0, 'r'
 	jalr	r40
 
@@ -176,10 +176,12 @@ STD_ENTRY(relocate_new_kernel)
 
 	/* we should not get here */
 
+#ifdef RELOCATE_NEW_KERNEL_VERBOSE
 	moveli	r0, '?'
 	jalr	r40
 	moveli	r0, '\n'
 	jalr	r40
+#endif
 
 	j	.Lhalt
 
@@ -237,7 +239,9 @@ STD_ENTRY(relocate_new_kernel)
 	j	.Lloop
 
 
-.Lerr:	moveli	r0, 'e'
+.Lerr:
+#ifdef RELOCATE_NEW_KERNEL_VERBOSE
+	moveli	r0, 'e'
 	jalr	r40
 	moveli	r0, 'r'
 	jalr	r40
@@ -245,6 +249,7 @@ STD_ENTRY(relocate_new_kernel)
 	jalr	r40
 	moveli	r0, '\n'
 	jalr	r40
+#endif
 .Lhalt:
 	moveli r41, hw2_last(hv_halt)
 	shl16insli r41, r41, hw1(hv_halt)
-- 
1.8.3.1

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