Isolate the access to user-memory in separate inline
functions. This open up for reuse from host-side virtioqueue
implementation accessing virtio-ring in kernel space.
Signed-off-by: Sjur Brændeland <sjur.brandeland@xxxxxxxxxxxxxx>
---
drivers/virtio/virtio_ring_host.c | 81 ++++++++++++++++++++++++++-----------
1 files changed, 57 insertions(+), 24 deletions(-)
diff --git a/drivers/virtio/virtio_ring_host.c b/drivers/virtio/virtio_ring_host.c
index 192b838..0750099 100644
--- a/drivers/virtio/virtio_ring_host.c
+++ b/drivers/virtio/virtio_ring_host.c
@@ -18,44 +18,45 @@
#include <linux/virtio_ring.h>
#include <linux/module.h>
#include <linux/uaccess.h>
+#include <linux/kconfig.h>
MODULE_LICENSE("GPL");
-struct vring_used_elem *vring_add_used_user(struct vring_host *vh,
- unsigned int head, int len)
+
+static inline struct vring_used_elem *_vring_add_used(struct vring_host *vh,
+ u32 head, u32 len,
+ bool (*cpy)(void *dst,
+ void *src,
+ size_t s),
+ void (*wbarrier)(void))
{
struct vring_used_elem *used;
+ u16 last_used;
/* The virtqueue contains a ring of used buffers. Get a pointer to the
* next entry in that used ring. */
- used = &vh->vr.used->ring[vh->last_used_idx % vh->vr.num];
- if (__put_user(head, &used->id)) {
- pr_debug("Failed to write used id");
+ used = &vh->vr.used->ring[vh->last_used_idx & (vh->vr.num - 1)];
+ if (!cpy(&used->id, &head, sizeof(used->id)) ||
+ !cpy(&used->len, &len, sizeof(used->len)))
return NULL;
- }
- if (__put_user(len, &used->len)) {
- pr_debug("Failed to write used len");
+ wbarrier();
+ last_used = vh->last_used_idx + 1;
+ if (!cpy(&vh->vr.used->idx, &last_used, sizeof(vh->vr.used->idx)))
return NULL;
- }
- /* Make sure buffer is written before we update index. */
- smp_wmb();
- if (__put_user(vh->last_used_idx + 1, &vh->vr.used->idx)) {
- pr_debug("Failed to increment used idx");
- return NULL;
- }
- vh->last_used_idx++;
+ vh->last_used_idx = last_used;
return used;
}
-EXPORT_SYMBOL(vring_add_used_user);
-int vring_avail_desc_user(struct vring_host *vh)
+static inline int _vring_avail_desc(struct vring_host *vh,
+ bool (*get)(u16 *dst, u16 *src),
+ void (*read_barrier)(void))
{
- int head;
+ u16 head;
u16 last_avail_idx;
/* Check it isn't doing very strange things with descriptor numbers. */
last_avail_idx = vh->last_avail_idx;
- if (unlikely(__get_user(vh->avail_idx, &vh->vr.avail->idx))) {
+ if (unlikely(!get(&vh->avail_idx, &vh->vr.avail->idx))) {
pr_debug("Failed to access avail idx at %p\n",
&vh->vr.avail->idx);
return -EFAULT;
@@ -69,13 +70,12 @@ int vring_avail_desc_user(struct vring_host *vh)
return vh->vr.num;
/* Only get avail ring entries after they have been exposed by guest. */
- smp_rmb();
+ read_barrier();
/* Grab the next descriptor number they're advertising, and increment
* the index we've seen. */
- if (unlikely(__get_user(head,
- &vh->vr.avail->ring[last_avail_idx %
- vh->vr.num]))) {
+ if (unlikely(!get(&head, &vh->vr.avail->ring[last_avail_idx &
+ (vh->vr.num - 1)]))) {
pr_debug("Failed to read head: idx %d address %p\n",
last_avail_idx,
&vh->vr.avail->ring[last_avail_idx %
@@ -92,6 +92,39 @@ int vring_avail_desc_user(struct vring_host *vh)
return head;
}
+
+static inline void smp_write_barrier(void)
+{
+ smp_wmb();
+}
+
+static inline void smp_read_barrier(void)
+{
+ smp_rmb();
+}
+
+static inline bool userspace_cpy_to(void *dst, void *src, size_t s)
+{
+ return __copy_to_user(dst, src, s) == 0;
+}
+
+static inline bool userspace_get(u16 *dst, u16 *src)
+{
+ return __get_user(*dst, src);
+}
+
+struct vring_used_elem *vring_add_used_user(struct vring_host *vh,
+ unsigned int head, int len)
+{
+ return _vring_add_used(vh, head, len, userspace_cpy_to,
+ smp_write_barrier);
+}
+EXPORT_SYMBOL(vring_add_used_user);
+
+int vring_avail_desc_user(struct vring_host *vh)
+{
+ return _vring_avail_desc(vh, userspace_get, smp_read_barrier);
+}
EXPORT_SYMBOL(vring_avail_desc_user);
/* Each buffer in the virtqueues is actually a chain of descriptors. This
--
1.7.5.4
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