1 files changed, 211 insertions, 0 deletions
diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
new file mode 100644
index 000000000..ce6f3b916
--- /dev/null
+++ b/virt/kvm/coalesced_mmio.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KVM coalesced MMIO
+ *
+ * Copyright (c) 2008 Bull S.A.S.
+ * Copyright 2009 Red Hat, Inc. and/or its affiliates.
+ *
+ *  Author: Laurent Vivier <Laurent.Vivier@bull.net>
+ *
+ */
+
+#include <kvm/iodev.h>
+
+#include <linux/kvm_host.h>
+#include <linux/slab.h>
+#include <linux/kvm.h>
+
+#include "coalesced_mmio.h"
+
+static inline struct kvm_coalesced_mmio_dev *to_mmio(struct kvm_io_device *dev)
+{
+	return container_of(dev, struct kvm_coalesced_mmio_dev, dev);
+}
+
+static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
+				   gpa_t addr, int len)
+{
+	/* is it in a batchable area ?
+	 * (addr,len) is fully included in
+	 * (zone->addr, zone->size)
+	 */
+	if (len < 0)
+		return 0;
+	if (addr + len < addr)
+		return 0;
+	if (addr < dev->zone.addr)
+		return 0;
+	if (addr + len > dev->zone.addr + dev->zone.size)
+		return 0;
+	return 1;
+}
+
+static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev, u32 last)
+{
+	struct kvm_coalesced_mmio_ring *ring;
+	unsigned avail;
+
+	/* Are we able to batch it ? */
+
+	/* last is the first free entry
+	 * check if we don't meet the first used entry
+	 * there is always one unused entry in the buffer
+	 */
+	ring = dev->kvm->coalesced_mmio_ring;
+	avail = (ring->first - last - 1) % KVM_COALESCED_MMIO_MAX;
+	if (avail == 0) {
+		/* full */
+		return 0;
+	}
+
+	return 1;
+}
+
+static int coalesced_mmio_write(struct kvm_vcpu *vcpu,
+				struct kvm_io_device *this, gpa_t addr,
+				int len, const void *val)
+{
+	struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
+	struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
+	__u32 insert;
+
+	if (!coalesced_mmio_in_range(dev, addr, len))
+		return -EOPNOTSUPP;
+
+	spin_lock(&dev->kvm->ring_lock);
+
+	insert = READ_ONCE(ring->last);
+	if (!coalesced_mmio_has_room(dev, insert) ||
+	    insert >= KVM_COALESCED_MMIO_MAX) {
+		spin_unlock(&dev->kvm->ring_lock);
+		return -EOPNOTSUPP;
+	}
+
+	/* copy data in first free entry of the ring */
+
+	ring->coalesced_mmio[insert].phys_addr = addr;
+	ring->coalesced_mmio[insert].len = len;
+	memcpy(ring->coalesced_mmio[insert].data, val, len);
+	ring->coalesced_mmio[insert].pio = dev->zone.pio;
+	smp_wmb();
+	ring->last = (insert + 1) % KVM_COALESCED_MMIO_MAX;
+	spin_unlock(&dev->kvm->ring_lock);
+	return 0;
+}
+
+static void coalesced_mmio_destructor(struct kvm_io_device *this)
+{
+	struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
+
+	list_del(&dev->list);
+
+	kfree(dev);
+}
+
+static const struct kvm_io_device_ops coalesced_mmio_ops = {
+	.write      = coalesced_mmio_write,
+	.destructor = coalesced_mmio_destructor,
+};
+
+int kvm_coalesced_mmio_init(struct kvm *kvm)
+{
+	struct page *page;
+
+	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+	if (!page)
+		return -ENOMEM;
+
+	kvm->coalesced_mmio_ring = page_address(page);
+
+	/*
+	 * We're using this spinlock to sync access to the coalesced ring.
+	 * The list doesn't need its own lock since device registration and
+	 * unregistration should only happen when kvm->slots_lock is held.
+	 */
+	spin_lock_init(&kvm->ring_lock);
+	INIT_LIST_HEAD(&kvm->coalesced_zones);
+
+	return 0;
+}
+
+void kvm_coalesced_mmio_free(struct kvm *kvm)
+{
+	if (kvm->coalesced_mmio_ring)
+		free_page((unsigned long)kvm->coalesced_mmio_ring);
+}
+
+int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
+					 struct kvm_coalesced_mmio_zone *zone)
+{
+	int ret;
+	struct kvm_coalesced_mmio_dev *dev;
+
+	if (zone->pio != 1 && zone->pio != 0)
+		return -EINVAL;
+
+	dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev),
+		      GFP_KERNEL_ACCOUNT);
+	if (!dev)
+		return -ENOMEM;
+
+	kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
+	dev->kvm = kvm;
+	dev->zone = *zone;
+
+	mutex_lock(&kvm->slots_lock);
+	ret = kvm_io_bus_register_dev(kvm,
+				zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS,
+				zone->addr, zone->size, &dev->dev);
+	if (ret < 0)
+		goto out_free_dev;
+	list_add_tail(&dev->list, &kvm->coalesced_zones);
+	mutex_unlock(&kvm->slots_lock);
+
+	return 0;
+
+out_free_dev:
+	mutex_unlock(&kvm->slots_lock);
+	kfree(dev);
+
+	return ret;
+}
+
+int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
+					   struct kvm_coalesced_mmio_zone *zone)
+{
+	struct kvm_coalesced_mmio_dev *dev, *tmp;
+	int r;
+
+	if (zone->pio != 1 && zone->pio != 0)
+		return -EINVAL;
+
+	mutex_lock(&kvm->slots_lock);
+
+	list_for_each_entry_safe(dev, tmp, &kvm->coalesced_zones, list) {
+		if (zone->pio == dev->zone.pio &&
+		    coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
+			r = kvm_io_bus_unregister_dev(kvm,
+				zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);
+
+			kvm_iodevice_destructor(&dev->dev);
+
+			/*
+			 * On failure, unregister destroys all devices on the
+			 * bus _except_ the target device, i.e. coalesced_zones
+			 * has been modified.  Bail after destroying the target
+			 * device, there's no need to restart the walk as there
+			 * aren't any zones left.
+			 */
+			if (r)
+				break;
+		}
+	}
+
+	mutex_unlock(&kvm->slots_lock);
+
+	/*
+	 * Ignore the result of kvm_io_bus_unregister_dev(), from userspace's
+	 * perspective, the coalesced MMIO is most definitely unregistered.
+	 */
+	return 0;
+}