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Diffstat (limited to 'linux-headers/include/linux/virtio_ring.h')
-rw-r--r--linux-headers/include/linux/virtio_ring.h50
1 files changed, 39 insertions, 11 deletions
diff --git a/linux-headers/include/linux/virtio_ring.h b/linux-headers/include/linux/virtio_ring.h
index 370f7b8..0104834 100644
--- a/linux-headers/include/linux/virtio_ring.h
+++ b/linux-headers/include/linux/virtio_ring.h
@@ -84,6 +84,13 @@
* at the end of the used ring. Guest should ignore the used->flags field. */
#define VIRTIO_RING_F_EVENT_IDX 29
+/* Alignment requirements for vring elements.
+ * When using pre-virtio 1.0 layout, these fall out naturally.
+ */
+#define VRING_AVAIL_ALIGN_SIZE 2
+#define VRING_USED_ALIGN_SIZE 4
+#define VRING_DESC_ALIGN_SIZE 16
+
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
struct vring_desc {
/* Address (guest-physical). */
@@ -110,28 +117,47 @@ struct vring_used_elem {
__virtio32 len;
};
+typedef struct vring_used_elem __attribute__((aligned(VRING_USED_ALIGN_SIZE)))
+ vring_used_elem_t;
+
struct vring_used {
__virtio16 flags;
__virtio16 idx;
- struct vring_used_elem ring[];
+ vring_used_elem_t ring[];
};
+/*
+ * The ring element addresses are passed between components with different
+ * alignments assumptions. Thus, we might need to decrease the compiler-selected
+ * alignment, and so must use a typedef to make sure the aligned attribute
+ * actually takes hold:
+ *
+ * https://gcc.gnu.org/onlinedocs//gcc/Common-Type-Attributes.html#Common-Type-Attributes
+ *
+ * When used on a struct, or struct member, the aligned attribute can only
+ * increase the alignment; in order to decrease it, the packed attribute must
+ * be specified as well. When used as part of a typedef, the aligned attribute
+ * can both increase and decrease alignment, and specifying the packed
+ * attribute generates a warning.
+ */
+typedef struct vring_desc __attribute__((aligned(VRING_DESC_ALIGN_SIZE)))
+ vring_desc_t;
+typedef struct vring_avail __attribute__((aligned(VRING_AVAIL_ALIGN_SIZE)))
+ vring_avail_t;
+typedef struct vring_used __attribute__((aligned(VRING_USED_ALIGN_SIZE)))
+ vring_used_t;
+
struct vring {
unsigned int num;
- struct vring_desc *desc;
+ vring_desc_t *desc;
- struct vring_avail *avail;
+ vring_avail_t *avail;
- struct vring_used *used;
+ vring_used_t *used;
};
-/* Alignment requirements for vring elements.
- * When using pre-virtio 1.0 layout, these fall out naturally.
- */
-#define VRING_AVAIL_ALIGN_SIZE 2
-#define VRING_USED_ALIGN_SIZE 4
-#define VRING_DESC_ALIGN_SIZE 16
+#ifndef VIRTIO_RING_NO_LEGACY
/* The standard layout for the ring is a continuous chunk of memory which looks
* like this. We assume num is a power of 2.
@@ -167,7 +193,7 @@ static __inline__ void vring_init(struct vring *vr, unsigned int num, void *p,
{
vr->num = num;
vr->desc = p;
- vr->avail = p + num*sizeof(struct vring_desc);
+ vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc));
vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16)
+ align-1) & ~(align - 1));
}
@@ -179,6 +205,8 @@ static __inline__ unsigned vring_size(unsigned int num, unsigned long align)
+ sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num;
}
+#endif /* VIRTIO_RING_NO_LEGACY */
+
/* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
/* Assuming a given event_idx value from the other side, if
* we have just incremented index from old to new_idx,