KVM: Add coalesced MMIO support (common part)

This patch adds all needed structures to coalesce MMIOs.
Until an architecture uses it, it is not compiled.

Coalesced MMIO introduces two ioctl() to define where are the MMIO zones that
can be coalesced:

- KVM_REGISTER_COALESCED_MMIO registers a coalesced MMIO zone.
  It requests one parameter (struct kvm_coalesced_mmio_zone) which defines
  a memory area where MMIOs can be coalesced until the next switch to
  user space. The maximum number of MMIO zones is KVM_COALESCED_MMIO_ZONE_MAX.

- KVM_UNREGISTER_COALESCED_MMIO cancels all registered zones inside
  the given bounds (bounds are also given by struct kvm_coalesced_mmio_zone).

The userspace client can check kernel coalesced MMIO availability by asking
ioctl(KVM_CHECK_EXTENSION) for the KVM_CAP_COALESCED_MMIO capability.
The ioctl() call to KVM_CAP_COALESCED_MMIO will return 0 if not supported,
or the page offset where will be stored the ring buffer.
The page offset depends on the architecture.

After an ioctl(KVM_RUN), the first page of the KVM memory mapped points to
a kvm_run structure. The offset given by KVM_CAP_COALESCED_MMIO is
an offset to the coalesced MMIO ring expressed in PAGE_SIZE relatively
to the address of the start of th kvm_run structure. The MMIO ring buffer
is defined by the structure kvm_coalesced_mmio_ring.

[akio: fix oops during guest shutdown]

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Akio Takebe <takebe_akio@jp.fujitsu.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 156 insertions, 0 deletions

diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
new file mode 100644
index 000000000000..5ae620d32fac
--- /dev/null
+++ b/virt/kvm/coalesced_mmio.c
@@ -0,0 +1,156 @@
+/*
+ * KVM coalesced MMIO
+ *
+ * Copyright (c) 2008 Bull S.A.S.
+ *
+ *  Author: Laurent Vivier <Laurent.Vivier@bull.net>
+ *
+ */
+
+#include "iodev.h"
+
+#include <linux/kvm_host.h>
+#include <linux/kvm.h>
+
+#include "coalesced_mmio.h"
+
+static int coalesced_mmio_in_range(struct kvm_io_device *this,
+                                   gpa_t addr, int len, int is_write)
+{
+        struct kvm_coalesced_mmio_dev *dev =
+                                (struct kvm_coalesced_mmio_dev*)this->private;
+        struct kvm_coalesced_mmio_zone *zone;
+        int next;
+        int i;
+
+        if (!is_write)
+                return 0;
+
+        /* kvm->lock is taken by the caller and must be not released before
+         * dev.read/write
+         */
+
+        /* 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
+         */
+
+        next = (dev->kvm->coalesced_mmio_ring->last + 1) %
+                                                        KVM_COALESCED_MMIO_MAX;
+        if (next == dev->kvm->coalesced_mmio_ring->first) {
+                /* full */
+                return 0;
+        }
+
+        /* is it in a batchable area ? */
+
+        for (i = 0; i < dev->nb_zones; i++) {
+                zone = &dev->zone[i];
+
+                /* (addr,len) is fully included in
+                 * (zone->addr, zone->size)
+                 */
+
+                if (zone->addr <= addr &&
+                    addr + len <= zone->addr + zone->size)
+                        return 1;
+        }
+        return 0;
+}
+
+static void coalesced_mmio_write(struct kvm_io_device *this,
+                                 gpa_t addr, int len, const void *val)
+{
+        struct kvm_coalesced_mmio_dev *dev =
+                                (struct kvm_coalesced_mmio_dev*)this->private;
+        struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
+
+        /* kvm->lock must be taken by caller before call to in_range()*/
+
+        /* copy data in first free entry of the ring */
+
+        ring->coalesced_mmio[ring->last].phys_addr = addr;
+        ring->coalesced_mmio[ring->last].len = len;
+        memcpy(ring->coalesced_mmio[ring->last].data, val, len);
+        smp_wmb();
+        ring->last = (ring->last + 1) % KVM_COALESCED_MMIO_MAX;
+}
+
+static void coalesced_mmio_destructor(struct kvm_io_device *this)
+{
+        kfree(this);
+}
+
+int kvm_coalesced_mmio_init(struct kvm *kvm)
+{
+        struct kvm_coalesced_mmio_dev *dev;
+
+        dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev), GFP_KERNEL);
+        if (!dev)
+                return -ENOMEM;
+        dev->dev.write  = coalesced_mmio_write;
+        dev->dev.in_range  = coalesced_mmio_in_range;
+        dev->dev.destructor  = coalesced_mmio_destructor;
+        dev->dev.private  = dev;
+        dev->kvm = kvm;
+        kvm->coalesced_mmio_dev = dev;
+        kvm_io_bus_register_dev(&kvm->mmio_bus, &dev->dev);
+
+        return 0;
+}
+
+int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
+                                         struct kvm_coalesced_mmio_zone *zone)
+{
+        struct kvm_coalesced_mmio_dev *dev = kvm->coalesced_mmio_dev;
+
+        if (dev == NULL)
+                return -EINVAL;
+
+        mutex_lock(&kvm->lock);
+        if (dev->nb_zones >= KVM_COALESCED_MMIO_ZONE_MAX) {
+                mutex_unlock(&kvm->lock);
+                return -ENOBUFS;
+        }
+
+        dev->zone[dev->nb_zones] = *zone;
+        dev->nb_zones++;
+
+        mutex_unlock(&kvm->lock);
+        return 0;
+}
+
+int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
+                                           struct kvm_coalesced_mmio_zone *zone)
+{
+        int i;
+        struct kvm_coalesced_mmio_dev *dev = kvm->coalesced_mmio_dev;
+        struct kvm_coalesced_mmio_zone *z;
+
+        if (dev == NULL)
+                return -EINVAL;
+
+        mutex_lock(&kvm->lock);
+
+        i = dev->nb_zones;
+        while(i) {
+                z = &dev->zone[i - 1];
+
+                /* unregister all zones
+                 * included in (zone->addr, zone->size)
+                 */
+
+                if (zone->addr <= z->addr &&
+                    z->addr + z->size <= zone->addr + zone->size) {
+                        dev->nb_zones--;
+                        *z = dev->zone[dev->nb_zones];
+                }
+                i--;
+        }
+
+        mutex_unlock(&kvm->lock);
+
+        return 0;
+}