KVM: remove in_range from io devices

This changes bus accesses to use high-level kvm_io_bus_read/kvm_io_bus_write
functions. in_range now becomes unused so it is removed from device ops in
favor of read/write callbacks performing range checks internally.

This allows aliasing (mostly for in-kernel virtio), as well as better error
handling by making it possible to pass errors up to userspace.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

4 files changed, 50 insertions, 53 deletions

diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index 7b7cc9fe5ee3..0352f81ecc0b 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -19,18 +19,14 @@ 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_io_device *this,
-                                   gpa_t addr, int len, int is_write)
+static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
+                                   gpa_t addr, int len)
 {
-        struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
         struct kvm_coalesced_mmio_zone *zone;
         struct kvm_coalesced_mmio_ring *ring;
         unsigned avail;
         int i;
 
-        if (!is_write)
-                return 0;
-
         /* Are we able to batch it ? */
 
         /* last is the first free entry
@@ -60,11 +56,13 @@ static int coalesced_mmio_in_range(struct kvm_io_device *this,
         return 0;
 }
 
-static void coalesced_mmio_write(struct kvm_io_device *this,
-                                 gpa_t addr, int len, const void *val)
+static int coalesced_mmio_write(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;
+        if (!coalesced_mmio_in_range(dev, addr, len))
+                return -EOPNOTSUPP;
 
         spin_lock(&dev->lock);
 
@@ -76,6 +74,7 @@ static void coalesced_mmio_write(struct kvm_io_device *this,
         smp_wmb();
         ring->last = (ring->last + 1) % KVM_COALESCED_MMIO_MAX;
         spin_unlock(&dev->lock);
+        return 0;
 }
 
 static void coalesced_mmio_destructor(struct kvm_io_device *this)
@@ -87,7 +86,6 @@ static void coalesced_mmio_destructor(struct kvm_io_device *this)
 
 static const struct kvm_io_device_ops coalesced_mmio_ops = {
         .write      = coalesced_mmio_write,
-        .in_range   = coalesced_mmio_in_range,
         .destructor = coalesced_mmio_destructor,
 };
 
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 0eca54e06326..ddf6aa998b18 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -227,20 +227,19 @@ static inline struct kvm_ioapic *to_ioapic(struct kvm_io_device *dev)
         return container_of(dev, struct kvm_ioapic, dev);
 }
 
-static int ioapic_in_range(struct kvm_io_device *this, gpa_t addr,
-                           int len, int is_write)
+static inline int ioapic_in_range(struct kvm_ioapic *ioapic, gpa_t addr)
 {
-        struct kvm_ioapic *ioapic = to_ioapic(this);
-
         return ((addr >= ioapic->base_address &&
                  (addr < ioapic->base_address + IOAPIC_MEM_LENGTH)));
 }
 
-static void ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
-                             void *val)
+static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
+                            void *val)
 {
         struct kvm_ioapic *ioapic = to_ioapic(this);
         u32 result;
+        if (!ioapic_in_range(ioapic, addr))
+                return -EOPNOTSUPP;
 
         ioapic_debug("addr %lx\n", (unsigned long)addr);
         ASSERT(!(addr & 0xf));  /* check alignment */
@@ -273,13 +272,16 @@ static void ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
                 printk(KERN_WARNING "ioapic: wrong length %d\n", len);
         }
         mutex_unlock(&ioapic->kvm->irq_lock);
+        return 0;
 }
 
-static void ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
-                              const void *val)
+static int ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
+                             const void *val)
 {
         struct kvm_ioapic *ioapic = to_ioapic(this);
         u32 data;
+        if (!ioapic_in_range(ioapic, addr))
+                return -EOPNOTSUPP;
 
         ioapic_debug("ioapic_mmio_write addr=%p len=%d val=%p\n",
                      (void*)addr, len, val);
@@ -290,7 +292,7 @@ static void ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
                 data = *(u32 *) val;
         else {
                 printk(KERN_WARNING "ioapic: Unsupported size %d\n", len);
-                return;
+                return 0;
         }
 
         addr &= 0xff;
@@ -312,6 +314,7 @@ static void ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
                 break;
         }
         mutex_unlock(&ioapic->kvm->irq_lock);
+        return 0;
 }
 
 void kvm_ioapic_reset(struct kvm_ioapic *ioapic)
@@ -329,7 +332,6 @@ void kvm_ioapic_reset(struct kvm_ioapic *ioapic)
 static const struct kvm_io_device_ops ioapic_mmio_ops = {
         .read     = ioapic_mmio_read,
         .write    = ioapic_mmio_write,
-        .in_range = ioapic_in_range,
 };
 
 int kvm_ioapic_init(struct kvm *kvm)
diff --git a/virt/kvm/iodev.h b/virt/kvm/iodev.h
index 06e38b23fa61..12fd3caffd2b 100644
--- a/virt/kvm/iodev.h
+++ b/virt/kvm/iodev.h
@@ -17,23 +17,24 @@
 #define __KVM_IODEV_H__
 
 #include <linux/kvm_types.h>
+#include <asm/errno.h>
 
 struct kvm_io_device;
 
 /**
  * kvm_io_device_ops are called under kvm slots_lock.
+ * read and write handlers return 0 if the transaction has been handled,
+ * or non-zero to have it passed to the next device.
  **/
 struct kvm_io_device_ops {
-        void (*read)(struct kvm_io_device *this,
+        int (*read)(struct kvm_io_device *this,
+                    gpa_t addr,
+                    int len,
+                    void *val);
+        int (*write)(struct kvm_io_device *this,
                      gpa_t addr,
                      int len,
-                     void *val);
-        void (*write)(struct kvm_io_device *this,
-                      gpa_t addr,
-                      int len,
-                      const void *val);
-        int (*in_range)(struct kvm_io_device *this, gpa_t addr, int len,
-                        int is_write);
+                     const void *val);
         void (*destructor)(struct kvm_io_device *this);
 };
 
@@ -48,26 +49,16 @@ static inline void kvm_iodevice_init(struct kvm_io_device *dev,
         dev->ops = ops;
 }
 
-static inline void kvm_iodevice_read(struct kvm_io_device *dev,
-                                     gpa_t addr,
-                                     int len,
-                                     void *val)
+static inline int kvm_iodevice_read(struct kvm_io_device *dev,
+                                    gpa_t addr, int l, void *v)
 {
-        dev->ops->read(dev, addr, len, val);
+        return dev->ops->read ? dev->ops->read(dev, addr, l, v) : -EOPNOTSUPP;
 }
 
-static inline void kvm_iodevice_write(struct kvm_io_device *dev,
-                                      gpa_t addr,
-                                      int len,
-                                      const void *val)
+static inline int kvm_iodevice_write(struct kvm_io_device *dev,
+                                     gpa_t addr, int l, const void *v)
 {
-        dev->ops->write(dev, addr, len, val);
-}
-
-static inline int kvm_iodevice_in_range(struct kvm_io_device *dev,
-                                        gpa_t addr, int len, int is_write)
-{
-        return dev->ops->in_range(dev, addr, len, is_write);
+        return dev->ops->write ? dev->ops->write(dev, addr, l, v) : -EOPNOTSUPP;
 }
 
 static inline void kvm_iodevice_destructor(struct kvm_io_device *dev)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 0edc366ecf89..594606526620 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2512,19 +2512,25 @@ void kvm_io_bus_destroy(struct kvm_io_bus *bus)
         }
 }
 
-struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus,
-                                          gpa_t addr, int len, int is_write)
+/* kvm_io_bus_write - called under kvm->slots_lock */
+int kvm_io_bus_write(struct kvm_io_bus *bus, gpa_t addr,
+                     int len, const void *val)
 {
         int i;
+        for (i = 0; i < bus->dev_count; i++)
+                if (!kvm_iodevice_write(bus->devs[i], addr, len, val))
+                        return 0;
+        return -EOPNOTSUPP;
+}
 
-        for (i = 0; i < bus->dev_count; i++) {
-                struct kvm_io_device *pos = bus->devs[i];
-
-                if (kvm_iodevice_in_range(pos, addr, len, is_write))
-                        return pos;
-        }
-
-        return NULL;
+/* kvm_io_bus_read - called under kvm->slots_lock */
+int kvm_io_bus_read(struct kvm_io_bus *bus, gpa_t addr, int len, void *val)
+{
+        int i;
+        for (i = 0; i < bus->dev_count; i++)
+                if (!kvm_iodevice_read(bus->devs[i], addr, len, val))
+                        return 0;
+        return -EOPNOTSUPP;
 }
 
 void kvm_io_bus_register_dev(struct kvm *kvm, struct kvm_io_bus *bus,