Line data    Source code

       1             : /* SPDX-License-Identifier: GPL-2.0 */
       2             : #ifndef _LINUX_VIRTIO_RING_H
       3             : #define _LINUX_VIRTIO_RING_H
       4             : 
       5             : #include <asm/barrier.h>
       6             : #include <linux/irqreturn.h>
       7             : #include <uapi/linux/virtio_ring.h>
       8             : 
       9             : /*
      10             :  * Barriers in virtio are tricky.  Non-SMP virtio guests can't assume
      11             :  * they're not on an SMP host system, so they need to assume real
      12             :  * barriers.  Non-SMP virtio hosts could skip the barriers, but does
      13             :  * anyone care?
      14             :  *
      15             :  * For virtio_pci on SMP, we don't need to order with respect to MMIO
      16             :  * accesses through relaxed memory I/O windows, so virt_mb() et al are
      17             :  * sufficient.
      18             :  *
      19             :  * For using virtio to talk to real devices (eg. other heterogeneous
      20             :  * CPUs) we do need real barriers.  In theory, we could be using both
      21             :  * kinds of virtio, so it's a runtime decision, and the branch is
      22             :  * actually quite cheap.
      23             :  */
      24             : 
      25             : static inline void virtio_mb(bool weak_barriers)
      26             : {
      27           0 :         if (weak_barriers)
      28           0 :                 virt_mb();
      29             :         else
      30           0 :                 mb();
      31             : }
      32             : 
      33             : static inline void virtio_rmb(bool weak_barriers)
      34             : {
      35           0 :         if (weak_barriers)
      36           0 :                 virt_rmb();
      37             :         else
      38           0 :                 dma_rmb();
      39             : }
      40             : 
      41             : static inline void virtio_wmb(bool weak_barriers)
      42             : {
      43           0 :         if (weak_barriers)
      44           0 :                 virt_wmb();
      45             :         else
      46           0 :                 dma_wmb();
      47             : }
      48             : 
      49             : #define virtio_store_mb(weak_barriers, p, v) \
      50             : do { \
      51             :         if (weak_barriers) { \
      52             :                 virt_store_mb(*p, v); \
      53             :         } else { \
      54             :                 WRITE_ONCE(*p, v); \
      55             :                 mb(); \
      56             :         } \
      57             : } while (0) \
      58             : 
      59             : struct virtio_device;
      60             : struct virtqueue;
      61             : 
      62             : /*
      63             :  * Creates a virtqueue and allocates the descriptor ring.  If
      64             :  * may_reduce_num is set, then this may allocate a smaller ring than
      65             :  * expected.  The caller should query virtqueue_get_vring_size to learn
      66             :  * the actual size of the ring.
      67             :  */
      68             : struct virtqueue *vring_create_virtqueue(unsigned int index,
      69             :                                          unsigned int num,
      70             :                                          unsigned int vring_align,
      71             :                                          struct virtio_device *vdev,
      72             :                                          bool weak_barriers,
      73             :                                          bool may_reduce_num,
      74             :                                          bool ctx,
      75             :                                          bool (*notify)(struct virtqueue *vq),
      76             :                                          void (*callback)(struct virtqueue *vq),
      77             :                                          const char *name);
      78             : 
      79             : /*
      80             :  * Creates a virtqueue and allocates the descriptor ring with per
      81             :  * virtqueue DMA device.
      82             :  */
      83             : struct virtqueue *vring_create_virtqueue_dma(unsigned int index,
      84             :                                              unsigned int num,
      85             :                                              unsigned int vring_align,
      86             :                                              struct virtio_device *vdev,
      87             :                                              bool weak_barriers,
      88             :                                              bool may_reduce_num,
      89             :                                              bool ctx,
      90             :                                              bool (*notify)(struct virtqueue *vq),
      91             :                                              void (*callback)(struct virtqueue *vq),
      92             :                                              const char *name,
      93             :                                              struct device *dma_dev);
      94             : 
      95             : /*
      96             :  * Creates a virtqueue with a standard layout but a caller-allocated
      97             :  * ring.
      98             :  */
      99             : struct virtqueue *vring_new_virtqueue(unsigned int index,
     100             :                                       unsigned int num,
     101             :                                       unsigned int vring_align,
     102             :                                       struct virtio_device *vdev,
     103             :                                       bool weak_barriers,
     104             :                                       bool ctx,
     105             :                                       void *pages,
     106             :                                       bool (*notify)(struct virtqueue *vq),
     107             :                                       void (*callback)(struct virtqueue *vq),
     108             :                                       const char *name);
     109             : 
     110             : /*
     111             :  * Destroys a virtqueue.  If created with vring_create_virtqueue, this
     112             :  * also frees the ring.
     113             :  */
     114             : void vring_del_virtqueue(struct virtqueue *vq);
     115             : 
     116             : /* Filter out transport-specific feature bits. */
     117             : void vring_transport_features(struct virtio_device *vdev);
     118             : 
     119             : irqreturn_t vring_interrupt(int irq, void *_vq);
     120             : #endif /* _LINUX_VIRTIO_RING_H */