On 2018年05月29日 13:24, Tiwei Bie wrote:
On Tue, May 29, 2018 at 10:49:11AM +0800, Jason Wang wrote:
On 2018年05月22日 16:16, Tiwei Bie wrote:
This commit introduces the support for creating packed ring.
All split ring specific functions are added _split suffix.
Some necessary stubs for packed ring are also added.
Signed-off-by: Tiwei Bie <tiwei.bie@xxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 801 +++++++++++++++++++++++------------
include/linux/virtio_ring.h | 8 +-
2 files changed, 546 insertions(+), 263 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 71458f493cf8..f5ef5f42a7cf 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -61,11 +61,15 @@ struct vring_desc_state {
struct vring_desc *indir_desc; /* Indirect descriptor, if any. */
};
+struct vring_desc_state_packed {
+ int next; /* The next desc state. */
+};
+
struct vring_virtqueue {
struct virtqueue vq;
- /* Actual memory layout for this queue */
- struct vring vring;
+ /* Is this a packed ring? */
+ bool packed;
/* Can we use weak barriers? */
bool weak_barriers;
@@ -87,11 +91,39 @@ struct vring_virtqueue {
/* Last used index we've seen. */
u16 last_used_idx;
- /* Last written value to avail->flags */
- u16 avail_flags_shadow;
+ union {
+ /* Available for split ring */
+ struct {
+ /* Actual memory layout for this queue. */
+ struct vring vring;
- /* Last written value to avail->idx in guest byte order */
- u16 avail_idx_shadow;
+ /* Last written value to avail->flags */
+ u16 avail_flags_shadow;
+
+ /* Last written value to avail->idx in
+ * guest byte order. */
+ u16 avail_idx_shadow;
+ };
+
+ /* Available for packed ring */
+ struct {
+ /* Actual memory layout for this queue. */
+ struct vring_packed vring_packed;
+
+ /* Driver ring wrap counter. */
+ u8 avail_wrap_counter;
+
+ /* Device ring wrap counter. */
+ u8 used_wrap_counter;
How about just use boolean?
I can change it to bool if you want.
Yes, please.
[...]
-static int vring_mapping_error(const struct vring_virtqueue *vq,
- dma_addr_t addr)
-{
- if (!vring_use_dma_api(vq->vq.vdev))
- return 0;
-
- return dma_mapping_error(vring_dma_dev(vq), addr);
-}
It looks to me if you keep vring_mapping_error behind
vring_unmap_one_split(), lots of changes were unncessary.
[...]
+ }
+ /* That should have freed everything. */
+ BUG_ON(vq->vq.num_free != vq->vring.num);
+
+ END_USE(vq);
+ return NULL;
+}
I think the those copy-and-paste hunks could be avoided and the diff should
only contains renaming of the function. If yes, it would be very welcomed
since it requires to compare the changes verbatim otherwise.
Michael suggested to lay out the code as:
XXX_split
XXX_packed
XXX wrappers
https://lkml.org/lkml/2018/4/13/410
That's why I moved some code.
I see, then no need to change but it still looks unnecessary.
+
+/*
+ * The layout for the packed ring is a continuous chunk of memory
+ * which looks like this.
+ *
+ * struct vring_packed {
+ * // The actual descriptors (16 bytes each)
+ * struct vring_packed_desc desc[num];
+ *
+ * // Padding to the next align boundary.
+ * char pad[];
+ *
+ * // Driver Event Suppression
+ * struct vring_packed_desc_event driver;
+ *
+ * // Device Event Suppression
+ * struct vring_packed_desc_event device;
+ * };
+ */
+static inline void vring_init_packed(struct vring_packed *vr, unsigned int num,
+ void *p, unsigned long align)
+{
+ vr->num = num;
+ vr->desc = p;
+ vr->driver = (void *)(((uintptr_t)p + sizeof(struct vring_packed_desc)
+ * num + align - 1) & ~(align - 1));
If we choose not to go uapi, maybe we can use ALIGN() macro here?
Okay.
+ vr->device = vr->driver + 1;
+}
[...]
+/* Only available for split ring */
const struct vring *virtqueue_get_vring(struct virtqueue *vq)
{
A possible issue with this is:
After commit d4674240f31f8c4289abba07d64291c6ddce51bc ("KVM: s390:
virtio-ccw revision 1 SET_VQ"). CCW tries to use
virtqueue_get_avail()/virtqueue_get_used(). Looks like a bug either here or
ccw code.
Do we still need to support:
include/linux/virtio.h
/*
* Legacy accessors -- in almost all cases, these are the wrong functions
* to use.
*/
static inline void *virtqueue_get_desc(struct virtqueue *vq)
{
return virtqueue_get_vring(vq)->desc;
}
static inline void *virtqueue_get_avail(struct virtqueue *vq)
{
return virtqueue_get_vring(vq)->avail;
}
static inline void *virtqueue_get_used(struct virtqueue *vq)
{
return virtqueue_get_vring(vq)->used;
}
in packed ring?
I think it was probably a bug in ccw, they should use e.g
virtqueue_get_desc_addr() instead.
Thanks
If so, I think maybe it's better to expose them as
symbols and implement them in virtio_ring.c.
Best regards,
Tiwei Bie
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