1 files changed, 338 insertions, 0 deletions
diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
new file mode 100644
index 0000000..bbef376
--- /dev/null
+++ b/drivers/s390/kvm/kvm_virtio.c
@@ -0,0 +1,338 @@
+/*
+ * 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@de.ibm.com>
+ */
+
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <linux/err.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/interrupt.h>
+#include <linux/virtio_ring.h>
+#include <asm/io.h>
+#include <asm/kvm_para.h>
+#include <asm/kvm_virtio.h>
+#include <asm/setup.h>
+#include <asm/s390_ext.h>
+
+#define VIRTIO_SUBCODE_64 0x0D00
+
+/*
+ * The pointer to our (page) of device descriptions.
+ */
+static void *kvm_devices;
+
+/*
+ * Unique numbering for kvm devices.
+ */
+static unsigned int dev_index;
+
+struct kvm_device {
+	struct virtio_device vdev;
+	struct kvm_device_desc *desc;
+};
+
+#define to_kvmdev(vd) container_of(vd, struct kvm_device, vdev)
+
+/*
+ * memory layout:
+ * - kvm_device_descriptor
+ *        struct kvm_device_desc
+ * - configuration
+ *        struct kvm_vqconfig
+ * - feature bits
+ * - config space
+ */
+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 tests (and acknowleges) a feature bit.
+ */
+static bool kvm_feature(struct virtio_device *vdev, unsigned fbit)
+{
+	struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
+	u8 *features;
+
+	if (fbit / 8 > desc->feature_len)
+		return false;
+
+	features = kvm_vq_features(desc);
+	if (!(features[fbit / 8] & (1 << (fbit % 8))))
+		return false;
+
+	/*
+	 * We set the matching bit in the other half of the bitmap to tell the
+	 * Host we want to use this feature.
+	 */
+	features[desc->feature_len + fbit / 8] |= (1 << (fbit % 8));
+	return true;
+}
+
+/*
+ * 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;
+	kvm_hypercall1(KVM_S390_VIRTIO_SET_STATUS,
+		       (unsigned long) to_kvmdev(vdev)->desc);
+}
+
+/*
+ * 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)
+{
+	kvm_hypercall1(KVM_S390_VIRTIO_RESET,
+		       (unsigned long) to_kvmdev(vdev)->desc);
+}
+
+/*
+ * 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_vqconfig *config = vq->priv;
+
+	kvm_hypercall1(KVM_S390_VIRTIO_NOTIFY, config->address);
+}
+
+/*
+ * 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))
+{
+	struct kvm_device *kdev = to_kvmdev(vdev);
+	struct kvm_vqconfig *config;
+	struct virtqueue *vq;
+	int err;
+
+	if (index >= kdev->desc->num_vq)
+		return ERR_PTR(-ENOENT);
+
+	config = kvm_vq_config(kdev->desc)+index;
+
+	if (add_shared_memory(config->address,
+				vring_size(config->num, PAGE_SIZE))) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	vq = vring_new_virtqueue(config->num, vdev, (void *) config->address,
+				 kvm_notify, callback);
+	if (!vq) {
+		err = -ENOMEM;
+		goto unmap;
+	}
+
+	/*
+	 * register a callback token
+	 * The host will sent this via the external interrupt parameter
+	 */
+	config->token = (u64) vq;
+
+	vq->priv = config;
+	return vq;
+unmap:
+	remove_shared_memory(config->address, vring_size(config->num,
+			     PAGE_SIZE));
+out:
+	return ERR_PTR(err);
+}
+
+static void kvm_del_vq(struct virtqueue *vq)
+{
+	struct kvm_vqconfig *config = vq->priv;
+
+	vring_del_virtqueue(vq);
+	remove_shared_memory(config->address,
+			     vring_size(config->num, PAGE_SIZE));
+}
+
+/*
+ * The config ops structure as defined by virtio config
+ */
+static struct virtio_config_ops kvm_vq_configspace_ops = {
+	.feature = kvm_feature,
+	.get = kvm_get,
+	.set = kvm_set,
+	.get_status = kvm_get_status,
+	.set_status = kvm_set_status,
+	.reset = kvm_reset,
+	.find_vq = kvm_find_vq,
+	.del_vq = kvm_del_vq,
+};
+
+/*
+ * The root device for the kvm virtio devices.
+ * This makes them appear as /sys/devices/kvm_s390/0,1,2 not /sys/devices/0,1,2.
+ */
+static struct device kvm_root = {
+	.parent = NULL,
+	.bus_id = "kvm_s390",
+};
+
+/*
+ * 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)
+{
+	struct kvm_device *kdev;
+
+	kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
+	if (!kdev) {
+		printk(KERN_EMERG "Cannot allocate kvm dev %u\n",
+		       dev_index++);
+		return;
+	}
+
+	kdev->vdev.dev.parent = &kvm_root;
+	kdev->vdev.index = dev_index++;
+	kdev->vdev.id.device = d->type;
+	kdev->vdev.config = &kvm_vq_configspace_ops;
+	kdev->desc = d;
+
+	if (register_virtio_device(&kdev->vdev) != 0) {
+		printk(KERN_ERR "Failed to register kvm device %u\n",
+		       kdev->vdev.index);
+		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);
+	}
+}
+
+/*
+ * we emulate the request_irq behaviour on top of s390 extints
+ */
+static void kvm_extint_handler(u16 code)
+{
+	void *data = (void *) *(long *) __LC_PFAULT_INTPARM;
+	u16 subcode = S390_lowcore.cpu_addr;
+
+	if ((subcode & 0xff00) != VIRTIO_SUBCODE_64)
+		return;
+
+	vring_interrupt(0, data);
+}
+
+/*
+ * Init function for virtio
+ * devices are in a single page above top of "normal" mem
+ */
+static int __init kvm_devices_init(void)
+{
+	int rc;
+
+	if (!MACHINE_IS_KVM)
+		return -ENODEV;
+
+	rc = device_register(&kvm_root);
+	if (rc) {
+		printk(KERN_ERR "Could not register kvm_s390 root device");
+		return rc;
+	}
+
+	if (add_shared_memory((max_pfn) << PAGE_SHIFT, PAGE_SIZE)) {
+		device_unregister(&kvm_root);
+		return -ENOMEM;
+	}
+
+	kvm_devices  = (void *) (max_pfn << PAGE_SHIFT);
+
+	ctl_set_bit(0, 9);
+	register_external_interrupt(0x2603, kvm_extint_handler);
+
+	scan_devices();
+	return 0;
+}
+
+/*
+ * We do this after core stuff, but before the drivers.
+ */
+postcore_initcall(kvm_devices_init);