Hello everyone, This RFC implements packed ring support in virtio driver. Some simple functional tests have been done with Jason's packed ring implementation in vhost: https://lkml.org/lkml/2018/4/23/12 Both of ping and netperf worked as expected (with EVENT_IDX disabled). But there are below known issues: 1. Reloading the guest driver will break the Tx/Rx; 2. Zeroing the flags when detaching a used desc will break the guest -> host path. Some simple functional tests have also been done with Wei's packed ring implementation in QEMU: http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg00342.html Both of ping and netperf worked as expected (with EVENT_IDX disabled). Reloading the guest driver also worked as expected. TODO: - Refinements (for code and commit log) and bug fixes; - Discuss/fix/test EVENT_IDX support; - Test devices other than net; RFC v2 -> RFC v3: - Split into small patches (Jason); - Add helper virtqueue_use_indirect() (Jason); - Just set id for the last descriptor of a list (Jason); - Calculate the prev in virtqueue_add_packed() (Jason); - Fix/improve desc suppression code (Jason/MST); - Refine the code layout for XXX_split/packed and wrappers (MST); - Fix the comments and API in uapi (MST); - Remove the BUG_ON() for indirect (Jason); - Some other refinements and bug fixes; RFC v1 -> RFC v2: - Add indirect descriptor support - compile test only; - Add event suppression supprt - compile test only; - Move vring_packed_init() out of uapi (Jason, MST); - Merge two loops into one in virtqueue_add_packed() (Jason); - Split vring_unmap_one() for packed ring and split ring (Jason); - Avoid using '%' operator (Jason); - Rename free_head -> next_avail_idx (Jason); - Add comments for virtio_wmb() in virtqueue_add_packed() (Jason); - Some other refinements and bug fixes; Thanks! Tiwei Bie (5): virtio: add packed ring definitions virtio_ring: support creating packed ring virtio_ring: add packed ring support virtio_ring: add event idx support in packed ring virtio_ring: enable packed ring drivers/virtio/virtio_ring.c | 1271 ++++++++++++++++++++++++++++-------- include/linux/virtio_ring.h | 8 +- include/uapi/linux/virtio_config.h | 12 +- include/uapi/linux/virtio_ring.h | 36 + 4 files changed, 1049 insertions(+), 278 deletions(-) -- 2.11.0
Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
---
include/uapi/linux/virtio_config.h | 12 +++++++++++-
include/uapi/linux/virtio_ring.h | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/virtio_config.h
b/include/uapi/linux/virtio_config.h
index 308e2096291f..a6e392325e3a 100644
--- a/include/uapi/linux/virtio_config.h
+++ b/include/uapi/linux/virtio_config.h
@@ -49,7 +49,7 @@
* transport being used (eg. virtio_ring), the rest are per-device feature
* bits. */
#define VIRTIO_TRANSPORT_F_START 28
-#define VIRTIO_TRANSPORT_F_END 34
+#define VIRTIO_TRANSPORT_F_END 36
#ifndef VIRTIO_CONFIG_NO_LEGACY
/* Do we get callbacks when the ring is completely used, even if we've
@@ -71,4 +71,14 @@
* this is for compatibility with legacy systems.
*/
#define VIRTIO_F_IOMMU_PLATFORM 33
+
+/* This feature indicates support for the packed virtqueue layout. */
+#define VIRTIO_F_RING_PACKED 34
+
+/*
+ * This feature indicates that all buffers are used by the device
+ * in the same order in which they have been made available.
+ */
+#define VIRTIO_F_IN_ORDER 35
+
#endif /* _UAPI_LINUX_VIRTIO_CONFIG_H */
diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h
index 6d5d5faa989b..3932cb80c347 100644
--- a/include/uapi/linux/virtio_ring.h
+++ b/include/uapi/linux/virtio_ring.h
@@ -44,6 +44,9 @@
/* This means the buffer contains a list of buffer descriptors. */
#define VRING_DESC_F_INDIRECT 4
+#define VRING_DESC_F_AVAIL(b) ((b) << 7)
+#define VRING_DESC_F_USED(b) ((b) << 15)
+
/* The Host uses this in used->flags to advise the Guest: don't kick me
when
* you add a buffer. It's unreliable, so it's simply an optimization.
Guest
* will still kick if it's out of buffers. */
@@ -53,6 +56,10 @@
* optimization. */
#define VRING_AVAIL_F_NO_INTERRUPT 1
+#define VRING_EVENT_F_ENABLE 0x0
+#define VRING_EVENT_F_DISABLE 0x1
+#define VRING_EVENT_F_DESC 0x2
+
/* We support indirect buffer descriptors */
#define VIRTIO_RING_F_INDIRECT_DESC 28
@@ -171,4 +178,33 @@ static inline int vring_need_event(__u16 event_idx, __u16
new_idx, __u16 old)
return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);
}
+struct vring_packed_desc_event {
+ /* __virtio16 off : 15; // Descriptor Event Offset
+ * __virtio16 wrap : 1; // Descriptor Event Wrap Counter */
+ __virtio16 off_wrap;
+ /* __virtio16 flags : 2; // Descriptor Event Flags */
+ __virtio16 flags;
+};
+
+struct vring_packed_desc {
+ /* Buffer Address. */
+ __virtio64 addr;
+ /* Buffer Length. */
+ __virtio32 len;
+ /* Buffer ID. */
+ __virtio16 id;
+ /* The flags depending on descriptor type. */
+ __virtio16 flags;
+};
+
+struct vring_packed {
+ unsigned int num;
+
+ struct vring_packed_desc *desc;
+
+ struct vring_packed_desc_event *driver;
+
+ struct vring_packed_desc_event *device;
+};
+
#endif /* _UAPI_LINUX_VIRTIO_RING_H */
--
2.11.0
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 at intel.com>
---
drivers/virtio/virtio_ring.c | 764 ++++++++++++++++++++++++++++---------------
include/linux/virtio_ring.h | 8 +-
2 files changed, 513 insertions(+), 259 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 71458f493cf8..e164822ca66e 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -64,8 +64,8 @@ struct vring_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;
@@ -79,19 +79,45 @@ struct vring_virtqueue {
/* Host publishes avail event idx */
bool event;
- /* Head of free buffer list. */
- unsigned int free_head;
/* Number we've added since last sync. */
unsigned int num_added;
/* 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;
+ /* Head of free buffer list. */
+ unsigned int free_head;
+
+ /* 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 wrap_counter;
+
+ /* Index of the next avail descriptor. */
+ unsigned int next_avail_idx;
+
+ /* Last written value to driver->flags in
+ * guest byte order. */
+ u16 event_flags_shadow;
+ };
+ };
/* How to notify other side. FIXME: commonalize hcalls! */
bool (*notify)(struct virtqueue *vq);
@@ -201,8 +227,17 @@ static dma_addr_t vring_map_single(const struct
vring_virtqueue *vq,
cpu_addr, size, direction);
}
-static void vring_unmap_one(const struct vring_virtqueue *vq,
- struct vring_desc *desc)
+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);
+}
+
+static void vring_unmap_one_split(const struct vring_virtqueue *vq,
+ struct vring_desc *desc)
{
u16 flags;
@@ -226,17 +261,9 @@ static void vring_unmap_one(const struct vring_virtqueue
*vq,
}
}
-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);
-}
-
-static struct vring_desc *alloc_indirect(struct virtqueue *_vq,
- unsigned int total_sg, gfp_t gfp)
+static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq,
+ unsigned int total_sg,
+ gfp_t gfp)
{
struct vring_desc *desc;
unsigned int i;
@@ -257,14 +284,14 @@ static struct vring_desc *alloc_indirect(struct virtqueue
*_vq,
return desc;
}
-static inline int virtqueue_add(struct virtqueue *_vq,
- struct scatterlist *sgs[],
- unsigned int total_sg,
- unsigned int out_sgs,
- unsigned int in_sgs,
- void *data,
- void *ctx,
- gfp_t gfp)
+static inline int virtqueue_add_split(struct virtqueue *_vq,
+ struct scatterlist *sgs[],
+ unsigned int total_sg,
+ unsigned int out_sgs,
+ unsigned int in_sgs,
+ void *data,
+ void *ctx,
+ gfp_t gfp)
{
struct vring_virtqueue *vq = to_vvq(_vq);
struct scatterlist *sg;
@@ -303,7 +330,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
/* If the host supports indirect descriptor tables, and we have multiple
* buffers, then go indirect. FIXME: tune this threshold */
if (vq->indirect && total_sg > 1 && vq->vq.num_free)
- desc = alloc_indirect(_vq, total_sg, gfp);
+ desc = alloc_indirect_split(_vq, total_sg, gfp);
else {
desc = NULL;
WARN_ON_ONCE(total_sg > vq->vring.num && !vq->indirect);
@@ -424,7 +451,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
for (n = 0; n < total_sg; n++) {
if (i == err_idx)
break;
- vring_unmap_one(vq, &desc[i]);
+ vring_unmap_one_split(vq, &desc[i]);
i = virtio16_to_cpu(_vq->vdev, vq->vring.desc[i].next);
}
@@ -435,6 +462,355 @@ static inline int virtqueue_add(struct virtqueue *_vq,
return -EIO;
}
+static bool virtqueue_kick_prepare_split(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ u16 new, old;
+ bool needs_kick;
+
+ START_USE(vq);
+ /* We need to expose available array entries before checking avail
+ * event. */
+ virtio_mb(vq->weak_barriers);
+
+ old = vq->avail_idx_shadow - vq->num_added;
+ new = vq->avail_idx_shadow;
+ vq->num_added = 0;
+
+#ifdef DEBUG
+ if (vq->last_add_time_valid) {
+ WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
+ vq->last_add_time)) > 100);
+ }
+ vq->last_add_time_valid = false;
+#endif
+
+ if (vq->event) {
+ needs_kick = vring_need_event(virtio16_to_cpu(_vq->vdev,
vring_avail_event(&vq->vring)),
+ new, old);
+ } else {
+ needs_kick = !(vq->vring.used->flags &
cpu_to_virtio16(_vq->vdev, VRING_USED_F_NO_NOTIFY));
+ }
+ END_USE(vq);
+ return needs_kick;
+}
+
+static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
+ void **ctx)
+{
+ unsigned int i, j;
+ __virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
+
+ /* Clear data ptr. */
+ vq->desc_state[head].data = NULL;
+
+ /* Put back on free list: unmap first-level descriptors and find end */
+ i = head;
+
+ while (vq->vring.desc[i].flags & nextflag) {
+ vring_unmap_one_split(vq, &vq->vring.desc[i]);
+ i = virtio16_to_cpu(vq->vq.vdev, vq->vring.desc[i].next);
+ vq->vq.num_free++;
+ }
+
+ vring_unmap_one_split(vq, &vq->vring.desc[i]);
+ vq->vring.desc[i].next = cpu_to_virtio16(vq->vq.vdev, vq->free_head);
+ vq->free_head = head;
+
+ /* Plus final descriptor */
+ vq->vq.num_free++;
+
+ if (vq->indirect) {
+ struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
+ u32 len;
+
+ /* Free the indirect table, if any, now that it's unmapped. */
+ if (!indir_desc)
+ return;
+
+ len = virtio32_to_cpu(vq->vq.vdev, vq->vring.desc[head].len);
+
+ BUG_ON(!(vq->vring.desc[head].flags &
+ cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
+ BUG_ON(len == 0 || len % sizeof(struct vring_desc));
+
+ for (j = 0; j < len / sizeof(struct vring_desc); j++)
+ vring_unmap_one_split(vq, &indir_desc[j]);
+
+ kfree(indir_desc);
+ vq->desc_state[head].indir_desc = NULL;
+ } else if (ctx) {
+ *ctx = vq->desc_state[head].indir_desc;
+ }
+}
+
+static inline bool more_used_split(const struct vring_virtqueue *vq)
+{
+ return vq->last_used_idx != virtio16_to_cpu(vq->vq.vdev,
vq->vring.used->idx);
+}
+
+static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq,
+ unsigned int *len,
+ void **ctx)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ void *ret;
+ unsigned int i;
+ u16 last_used;
+
+ START_USE(vq);
+
+ if (unlikely(vq->broken)) {
+ END_USE(vq);
+ return NULL;
+ }
+
+ if (!more_used_split(vq)) {
+ pr_debug("No more buffers in queue\n");
+ END_USE(vq);
+ return NULL;
+ }
+
+ /* Only get used array entries after they have been exposed by host. */
+ virtio_rmb(vq->weak_barriers);
+
+ last_used = (vq->last_used_idx & (vq->vring.num - 1));
+ i = virtio32_to_cpu(_vq->vdev, vq->vring.used->ring[last_used].id);
+ *len = virtio32_to_cpu(_vq->vdev,
vq->vring.used->ring[last_used].len);
+
+ if (unlikely(i >= vq->vring.num)) {
+ BAD_RING(vq, "id %u out of range\n", i);
+ return NULL;
+ }
+ if (unlikely(!vq->desc_state[i].data)) {
+ BAD_RING(vq, "id %u is not a head!\n", i);
+ return NULL;
+ }
+
+ /* detach_buf_split clears data, so grab it now. */
+ ret = vq->desc_state[i].data;
+ detach_buf_split(vq, i, ctx);
+ vq->last_used_idx++;
+ /* If we expect an interrupt for the next entry, tell host
+ * by writing event index and flush out the write before
+ * the read in the next get_buf call. */
+ if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT))
+ virtio_store_mb(vq->weak_barriers,
+ &vring_used_event(&vq->vring),
+ cpu_to_virtio16(_vq->vdev, vq->last_used_idx));
+
+#ifdef DEBUG
+ vq->last_add_time_valid = false;
+#endif
+
+ END_USE(vq);
+ return ret;
+}
+
+static void virtqueue_disable_cb_split(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+
+ if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
+ vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
+ if (!vq->event)
+ vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev,
vq->avail_flags_shadow);
+ }
+}
+
+static unsigned virtqueue_enable_cb_prepare_split(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ u16 last_used_idx;
+
+ START_USE(vq);
+
+ /* We optimistically turn back on interrupts, then check if there was
+ * more to do. */
+ /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
+ * either clear the flags bit or point the event index at the next
+ * entry. Always do both to keep code simple. */
+ if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
+ vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
+ if (!vq->event)
+ vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev,
vq->avail_flags_shadow);
+ }
+ vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev,
last_used_idx = vq->last_used_idx);
+ END_USE(vq);
+ return last_used_idx;
+}
+
+static bool virtqueue_poll_split(struct virtqueue *_vq, unsigned last_used_idx)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+
+ virtio_mb(vq->weak_barriers);
+ return (u16)last_used_idx != virtio16_to_cpu(_vq->vdev,
vq->vring.used->idx);
+}
+
+static bool virtqueue_enable_cb_delayed_split(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ u16 bufs;
+
+ START_USE(vq);
+
+ /* We optimistically turn back on interrupts, then check if there was
+ * more to do. */
+ /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
+ * either clear the flags bit or point the event index at the next
+ * entry. Always update the event index to keep code simple. */
+ if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
+ vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
+ if (!vq->event)
+ vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev,
vq->avail_flags_shadow);
+ }
+ /* TODO: tune this threshold */
+ bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4;
+
+ virtio_store_mb(vq->weak_barriers,
+ &vring_used_event(&vq->vring),
+ cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs));
+
+ if (unlikely((u16)(virtio16_to_cpu(_vq->vdev, vq->vring.used->idx) -
vq->last_used_idx) > bufs)) {
+ END_USE(vq);
+ return false;
+ }
+
+ END_USE(vq);
+ return true;
+}
+
+static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ unsigned int i;
+ void *buf;
+
+ START_USE(vq);
+
+ for (i = 0; i < vq->vring.num; i++) {
+ if (!vq->desc_state[i].data)
+ continue;
+ /* detach_buf clears data, so grab it now. */
+ buf = vq->desc_state[i].data;
+ detach_buf_split(vq, i, NULL);
+ vq->avail_idx_shadow--;
+ vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev,
vq->avail_idx_shadow);
+ END_USE(vq);
+ return buf;
+ }
+ /* That should have freed everything. */
+ BUG_ON(vq->vq.num_free != vq->vring.num);
+
+ END_USE(vq);
+ return NULL;
+}
+
+/*
+ * 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));
+ vr->device = vr->driver + 1;
+}
+
+static inline unsigned vring_size_packed(unsigned int num, unsigned long align)
+{
+ return ((sizeof(struct vring_packed_desc) * num + align - 1)
+ & ~(align - 1)) + sizeof(struct vring_packed_desc_event) * 2;
+}
+
+static inline int virtqueue_add_packed(struct virtqueue *_vq,
+ struct scatterlist *sgs[],
+ unsigned int total_sg,
+ unsigned int out_sgs,
+ unsigned int in_sgs,
+ void *data,
+ void *ctx,
+ gfp_t gfp)
+{
+ return -EIO;
+}
+
+static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq)
+{
+ return false;
+}
+
+static inline bool more_used_packed(const struct vring_virtqueue *vq)
+{
+ return false;
+}
+
+static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
+ unsigned int *len,
+ void **ctx)
+{
+ return NULL;
+}
+
+static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
+{
+}
+
+static unsigned virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq)
+{
+ return 0;
+}
+
+static bool virtqueue_poll_packed(struct virtqueue *_vq, unsigned
last_used_idx)
+{
+ return false;
+}
+
+static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq)
+{
+ return false;
+}
+
+static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
+{
+ return NULL;
+}
+
+static inline int virtqueue_add(struct virtqueue *_vq,
+ struct scatterlist *sgs[],
+ unsigned int total_sg,
+ unsigned int out_sgs,
+ unsigned int in_sgs,
+ void *data,
+ void *ctx,
+ gfp_t gfp)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+
+ return vq->packed ? virtqueue_add_packed(_vq, sgs, total_sg, out_sgs,
+ in_sgs, data, ctx, gfp) :
+ virtqueue_add_split(_vq, sgs, total_sg, out_sgs,
+ in_sgs, data, ctx, gfp);
+}
+
/**
* virtqueue_add_sgs - expose buffers to other end
* @vq: the struct virtqueue we're talking about.
@@ -551,34 +927,9 @@ EXPORT_SYMBOL_GPL(virtqueue_add_inbuf_ctx);
bool virtqueue_kick_prepare(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- u16 new, old;
- bool needs_kick;
- START_USE(vq);
- /* We need to expose available array entries before checking avail
- * event. */
- virtio_mb(vq->weak_barriers);
-
- old = vq->avail_idx_shadow - vq->num_added;
- new = vq->avail_idx_shadow;
- vq->num_added = 0;
-
-#ifdef DEBUG
- if (vq->last_add_time_valid) {
- WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
- vq->last_add_time)) > 100);
- }
- vq->last_add_time_valid = false;
-#endif
-
- if (vq->event) {
- needs_kick = vring_need_event(virtio16_to_cpu(_vq->vdev,
vring_avail_event(&vq->vring)),
- new, old);
- } else {
- needs_kick = !(vq->vring.used->flags &
cpu_to_virtio16(_vq->vdev, VRING_USED_F_NO_NOTIFY));
- }
- END_USE(vq);
- return needs_kick;
+ return vq->packed ? virtqueue_kick_prepare_packed(_vq) :
+ virtqueue_kick_prepare_split(_vq);
}
EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
@@ -626,58 +977,9 @@ bool virtqueue_kick(struct virtqueue *vq)
}
EXPORT_SYMBOL_GPL(virtqueue_kick);
-static void detach_buf(struct vring_virtqueue *vq, unsigned int head,
- void **ctx)
-{
- unsigned int i, j;
- __virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
-
- /* Clear data ptr. */
- vq->desc_state[head].data = NULL;
-
- /* Put back on free list: unmap first-level descriptors and find end */
- i = head;
-
- while (vq->vring.desc[i].flags & nextflag) {
- vring_unmap_one(vq, &vq->vring.desc[i]);
- i = virtio16_to_cpu(vq->vq.vdev, vq->vring.desc[i].next);
- vq->vq.num_free++;
- }
-
- vring_unmap_one(vq, &vq->vring.desc[i]);
- vq->vring.desc[i].next = cpu_to_virtio16(vq->vq.vdev, vq->free_head);
- vq->free_head = head;
-
- /* Plus final descriptor */
- vq->vq.num_free++;
-
- if (vq->indirect) {
- struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
- u32 len;
-
- /* Free the indirect table, if any, now that it's unmapped. */
- if (!indir_desc)
- return;
-
- len = virtio32_to_cpu(vq->vq.vdev, vq->vring.desc[head].len);
-
- BUG_ON(!(vq->vring.desc[head].flags &
- cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
- BUG_ON(len == 0 || len % sizeof(struct vring_desc));
-
- for (j = 0; j < len / sizeof(struct vring_desc); j++)
- vring_unmap_one(vq, &indir_desc[j]);
-
- kfree(indir_desc);
- vq->desc_state[head].indir_desc = NULL;
- } else if (ctx) {
- *ctx = vq->desc_state[head].indir_desc;
- }
-}
-
static inline bool more_used(const struct vring_virtqueue *vq)
{
- return vq->last_used_idx != virtio16_to_cpu(vq->vq.vdev,
vq->vring.used->idx);
+ return vq->packed ? more_used_packed(vq) : more_used_split(vq);
}
/**
@@ -700,57 +1002,9 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq,
unsigned int *len,
void **ctx)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- void *ret;
- unsigned int i;
- u16 last_used;
- START_USE(vq);
-
- if (unlikely(vq->broken)) {
- END_USE(vq);
- return NULL;
- }
-
- if (!more_used(vq)) {
- pr_debug("No more buffers in queue\n");
- END_USE(vq);
- return NULL;
- }
-
- /* Only get used array entries after they have been exposed by host. */
- virtio_rmb(vq->weak_barriers);
-
- last_used = (vq->last_used_idx & (vq->vring.num - 1));
- i = virtio32_to_cpu(_vq->vdev, vq->vring.used->ring[last_used].id);
- *len = virtio32_to_cpu(_vq->vdev,
vq->vring.used->ring[last_used].len);
-
- if (unlikely(i >= vq->vring.num)) {
- BAD_RING(vq, "id %u out of range\n", i);
- return NULL;
- }
- if (unlikely(!vq->desc_state[i].data)) {
- BAD_RING(vq, "id %u is not a head!\n", i);
- return NULL;
- }
-
- /* detach_buf clears data, so grab it now. */
- ret = vq->desc_state[i].data;
- detach_buf(vq, i, ctx);
- vq->last_used_idx++;
- /* If we expect an interrupt for the next entry, tell host
- * by writing event index and flush out the write before
- * the read in the next get_buf call. */
- if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT))
- virtio_store_mb(vq->weak_barriers,
- &vring_used_event(&vq->vring),
- cpu_to_virtio16(_vq->vdev, vq->last_used_idx));
-
-#ifdef DEBUG
- vq->last_add_time_valid = false;
-#endif
-
- END_USE(vq);
- return ret;
+ return vq->packed ? virtqueue_get_buf_ctx_packed(_vq, len, ctx) :
+ virtqueue_get_buf_ctx_split(_vq, len, ctx);
}
EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx);
@@ -772,12 +1026,10 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
- vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
- if (!vq->event)
- vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev,
vq->avail_flags_shadow);
- }
-
+ if (vq->packed)
+ virtqueue_disable_cb_packed(_vq);
+ else
+ virtqueue_disable_cb_split(_vq);
}
EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
@@ -796,23 +1048,9 @@ EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- u16 last_used_idx;
- START_USE(vq);
-
- /* We optimistically turn back on interrupts, then check if there was
- * more to do. */
- /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
- * either clear the flags bit or point the event index at the next
- * entry. Always do both to keep code simple. */
- if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
- vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
- if (!vq->event)
- vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev,
vq->avail_flags_shadow);
- }
- vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev,
last_used_idx = vq->last_used_idx);
- END_USE(vq);
- return last_used_idx;
+ return vq->packed ? virtqueue_enable_cb_prepare_packed(_vq) :
+ virtqueue_enable_cb_prepare_split(_vq);
}
EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
@@ -829,8 +1067,8 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned
last_used_idx)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- virtio_mb(vq->weak_barriers);
- return (u16)last_used_idx != virtio16_to_cpu(_vq->vdev,
vq->vring.used->idx);
+ return vq->packed ? virtqueue_poll_packed(_vq, last_used_idx) :
+ virtqueue_poll_split(_vq, last_used_idx);
}
EXPORT_SYMBOL_GPL(virtqueue_poll);
@@ -868,34 +1106,9 @@ EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- u16 bufs;
- START_USE(vq);
-
- /* We optimistically turn back on interrupts, then check if there was
- * more to do. */
- /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
- * either clear the flags bit or point the event index at the next
- * entry. Always update the event index to keep code simple. */
- if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
- vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
- if (!vq->event)
- vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev,
vq->avail_flags_shadow);
- }
- /* TODO: tune this threshold */
- bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4;
-
- virtio_store_mb(vq->weak_barriers,
- &vring_used_event(&vq->vring),
- cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs));
-
- if (unlikely((u16)(virtio16_to_cpu(_vq->vdev, vq->vring.used->idx) -
vq->last_used_idx) > bufs)) {
- END_USE(vq);
- return false;
- }
-
- END_USE(vq);
- return true;
+ return vq->packed ? virtqueue_enable_cb_delayed_packed(_vq) :
+ virtqueue_enable_cb_delayed_split(_vq);
}
EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
@@ -910,27 +1123,9 @@ EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- unsigned int i;
- void *buf;
- START_USE(vq);
-
- for (i = 0; i < vq->vring.num; i++) {
- if (!vq->desc_state[i].data)
- continue;
- /* detach_buf clears data, so grab it now. */
- buf = vq->desc_state[i].data;
- detach_buf(vq, i, NULL);
- vq->avail_idx_shadow--;
- vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev,
vq->avail_idx_shadow);
- END_USE(vq);
- return buf;
- }
- /* That should have freed everything. */
- BUG_ON(vq->vq.num_free != vq->vring.num);
-
- END_USE(vq);
- return NULL;
+ return vq->packed ? virtqueue_detach_unused_buf_packed(_vq) :
+ virtqueue_detach_unused_buf_split(_vq);
}
EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
@@ -955,7 +1150,8 @@ irqreturn_t vring_interrupt(int irq, void *_vq)
EXPORT_SYMBOL_GPL(vring_interrupt);
struct virtqueue *__vring_new_virtqueue(unsigned int index,
- struct vring vring,
+ union vring_union vring,
+ bool packed,
struct virtio_device *vdev,
bool weak_barriers,
bool context,
@@ -963,19 +1159,20 @@ struct virtqueue *__vring_new_virtqueue(unsigned int
index,
void (*callback)(struct virtqueue *),
const char *name)
{
- unsigned int i;
+ unsigned int num, i;
struct vring_virtqueue *vq;
- vq = kmalloc(sizeof(*vq) + vring.num * sizeof(struct vring_desc_state),
+ num = packed ? vring.vring_packed.num : vring.vring_split.num;
+
+ vq = kmalloc(sizeof(*vq) + num * sizeof(struct vring_desc_state),
GFP_KERNEL);
if (!vq)
return NULL;
- vq->vring = vring;
vq->vq.callback = callback;
vq->vq.vdev = vdev;
vq->vq.name = name;
- vq->vq.num_free = vring.num;
+ vq->vq.num_free = num;
vq->vq.index = index;
vq->we_own_ring = false;
vq->queue_dma_addr = 0;
@@ -984,9 +1181,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
vq->weak_barriers = weak_barriers;
vq->broken = false;
vq->last_used_idx = 0;
- vq->avail_flags_shadow = 0;
- vq->avail_idx_shadow = 0;
vq->num_added = 0;
+ vq->packed = packed;
list_add_tail(&vq->vq.list, &vdev->vqs);
#ifdef DEBUG
vq->in_use = false;
@@ -997,18 +1193,37 @@ struct virtqueue *__vring_new_virtqueue(unsigned int
index,
!context;
vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
+ if (vq->packed) {
+ vq->vring_packed = vring.vring_packed;
+ vq->next_avail_idx = 0;
+ vq->wrap_counter = 1;
+ vq->event_flags_shadow = 0;
+ } else {
+ vq->vring = vring.vring_split;
+ vq->avail_flags_shadow = 0;
+ vq->avail_idx_shadow = 0;
+
+ /* Put everything in free lists. */
+ vq->free_head = 0;
+ for (i = 0; i < num-1; i++)
+ vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1);
+ }
+
/* No callback? Tell other side not to bother us. */
if (!callback) {
- vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
- if (!vq->event)
- vq->vring.avail->flags = cpu_to_virtio16(vdev,
vq->avail_flags_shadow);
+ if (packed) {
+ vq->event_flags_shadow = VRING_EVENT_F_DISABLE;
+ vq->vring_packed.driver->flags = cpu_to_virtio16(vdev,
+ vq->event_flags_shadow);
+ } else {
+ vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
+ if (!vq->event)
+ vq->vring.avail->flags = cpu_to_virtio16(vdev,
+ vq->avail_flags_shadow);
+ }
}
- /* Put everything in free lists. */
- vq->free_head = 0;
- for (i = 0; i < vring.num-1; i++)
- vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1);
- memset(vq->desc_state, 0, vring.num * sizeof(struct vring_desc_state));
+ memset(vq->desc_state, 0, num * sizeof(struct vring_desc_state));
return &vq->vq;
}
@@ -1056,6 +1271,12 @@ static void vring_free_queue(struct virtio_device *vdev,
size_t size,
}
}
+static inline int
+__vring_size(unsigned int num, unsigned long align, bool packed)
+{
+ return packed ? vring_size_packed(num, align) : vring_size(num, align);
+}
+
struct virtqueue *vring_create_virtqueue(
unsigned int index,
unsigned int num,
@@ -1072,7 +1293,8 @@ struct virtqueue *vring_create_virtqueue(
void *queue = NULL;
dma_addr_t dma_addr;
size_t queue_size_in_bytes;
- struct vring vring;
+ union vring_union vring;
+ bool packed;
/* We assume num is a power of 2. */
if (num & (num - 1)) {
@@ -1080,9 +1302,13 @@ struct virtqueue *vring_create_virtqueue(
return NULL;
}
+ packed = virtio_has_feature(vdev, VIRTIO_F_RING_PACKED);
+
/* TODO: allocate each queue chunk individually */
- for (; num && vring_size(num, vring_align) > PAGE_SIZE; num /= 2) {
- queue = vring_alloc_queue(vdev, vring_size(num, vring_align),
+ for (; num && __vring_size(num, vring_align, packed) > PAGE_SIZE;
+ num /= 2) {
+ queue = vring_alloc_queue(vdev, __vring_size(num, vring_align,
+ packed),
&dma_addr,
GFP_KERNEL|__GFP_NOWARN|__GFP_ZERO);
if (queue)
@@ -1094,17 +1320,21 @@ struct virtqueue *vring_create_virtqueue(
if (!queue) {
/* Try to get a single page. You are my only hope! */
- queue = vring_alloc_queue(vdev, vring_size(num, vring_align),
+ queue = vring_alloc_queue(vdev, __vring_size(num, vring_align,
+ packed),
&dma_addr, GFP_KERNEL|__GFP_ZERO);
}
if (!queue)
return NULL;
- queue_size_in_bytes = vring_size(num, vring_align);
- vring_init(&vring, num, queue, vring_align);
+ queue_size_in_bytes = __vring_size(num, vring_align, packed);
+ if (packed)
+ vring_init_packed(&vring.vring_packed, num, queue, vring_align);
+ else
+ vring_init(&vring.vring_split, num, queue, vring_align);
- vq = __vring_new_virtqueue(index, vring, vdev, weak_barriers, context,
- notify, callback, name);
+ vq = __vring_new_virtqueue(index, vring, packed, vdev, weak_barriers,
+ context, notify, callback, name);
if (!vq) {
vring_free_queue(vdev, queue_size_in_bytes, queue,
dma_addr);
@@ -1130,10 +1360,17 @@ struct virtqueue *vring_new_virtqueue(unsigned int
index,
void (*callback)(struct virtqueue *vq),
const char *name)
{
- struct vring vring;
- vring_init(&vring, num, pages, vring_align);
- return __vring_new_virtqueue(index, vring, vdev, weak_barriers, context,
- notify, callback, name);
+ union vring_union vring;
+ bool packed;
+
+ packed = virtio_has_feature(vdev, VIRTIO_F_RING_PACKED);
+ if (packed)
+ vring_init_packed(&vring.vring_packed, num, pages, vring_align);
+ else
+ vring_init(&vring.vring_split, num, pages, vring_align);
+
+ return __vring_new_virtqueue(index, vring, packed, vdev, weak_barriers,
+ context, notify, callback, name);
}
EXPORT_SYMBOL_GPL(vring_new_virtqueue);
@@ -1143,7 +1380,9 @@ void vring_del_virtqueue(struct virtqueue *_vq)
if (vq->we_own_ring) {
vring_free_queue(vq->vq.vdev, vq->queue_size_in_bytes,
- vq->vring.desc, vq->queue_dma_addr);
+ vq->packed ? (void *)vq->vring_packed.desc :
+ (void *)vq->vring.desc,
+ vq->queue_dma_addr);
}
list_del(&_vq->list);
kfree(vq);
@@ -1185,7 +1424,7 @@ unsigned int virtqueue_get_vring_size(struct virtqueue
*_vq)
struct vring_virtqueue *vq = to_vvq(_vq);
- return vq->vring.num;
+ return vq->packed ? vq->vring_packed.num : vq->vring.num;
}
EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
@@ -1228,6 +1467,10 @@ dma_addr_t virtqueue_get_avail_addr(struct virtqueue
*_vq)
BUG_ON(!vq->we_own_ring);
+ if (vq->packed)
+ return vq->queue_dma_addr + ((char *)vq->vring_packed.driver -
+ (char *)vq->vring_packed.desc);
+
return vq->queue_dma_addr +
((char *)vq->vring.avail - (char *)vq->vring.desc);
}
@@ -1239,11 +1482,16 @@ dma_addr_t virtqueue_get_used_addr(struct virtqueue
*_vq)
BUG_ON(!vq->we_own_ring);
+ if (vq->packed)
+ return vq->queue_dma_addr + ((char *)vq->vring_packed.device -
+ (char *)vq->vring_packed.desc);
+
return vq->queue_dma_addr +
((char *)vq->vring.used - (char *)vq->vring.desc);
}
EXPORT_SYMBOL_GPL(virtqueue_get_used_addr);
+/* Only available for split ring */
const struct vring *virtqueue_get_vring(struct virtqueue *vq)
{
return &to_vvq(vq)->vring;
diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index bbf32524ab27..a0075894ad16 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -60,6 +60,11 @@ static inline void virtio_store_mb(bool weak_barriers,
struct virtio_device;
struct virtqueue;
+union vring_union {
+ struct vring vring_split;
+ struct vring_packed vring_packed;
+};
+
/*
* Creates a virtqueue and allocates the descriptor ring. If
* may_reduce_num is set, then this may allocate a smaller ring than
@@ -79,7 +84,8 @@ struct virtqueue *vring_create_virtqueue(unsigned int index,
/* Creates a virtqueue with a custom layout. */
struct virtqueue *__vring_new_virtqueue(unsigned int index,
- struct vring vring,
+ union vring_union vring,
+ bool packed,
struct virtio_device *vdev,
bool weak_barriers,
bool ctx,
--
2.11.0
This commit introduces the basic support (without EVENT_IDX)
for packed ring.
Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
---
drivers/virtio/virtio_ring.c | 444 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 434 insertions(+), 10 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index e164822ca66e..0181e93897be 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -58,7 +58,8 @@
struct vring_desc_state {
void *data; /* Data for callback. */
- struct vring_desc *indir_desc; /* Indirect descriptor, if any. */
+ void *indir_desc; /* Indirect descriptor, if any. */
+ int num; /* Descriptor list length. */
};
struct vring_virtqueue {
@@ -142,6 +143,16 @@ struct vring_virtqueue {
#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
+static inline bool virtqueue_use_indirect(struct virtqueue *_vq,
+ unsigned int total_sg)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+
+ /* If the host supports indirect descriptor tables, and we have multiple
+ * buffers, then go indirect. FIXME: tune this threshold */
+ return (vq->indirect && total_sg > 1 &&
vq->vq.num_free);
+}
+
/*
* Modern virtio devices have feature bits to specify whether they need a
* quirk and bypass the IOMMU. If not there, just use the DMA API.
@@ -327,9 +338,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
head = vq->free_head;
- /* If the host supports indirect descriptor tables, and we have multiple
- * buffers, then go indirect. FIXME: tune this threshold */
- if (vq->indirect && total_sg > 1 && vq->vq.num_free)
+ if (virtqueue_use_indirect(_vq, total_sg))
desc = alloc_indirect_split(_vq, total_sg, gfp);
else {
desc = NULL;
@@ -741,6 +750,49 @@ static inline unsigned vring_size_packed(unsigned int num,
unsigned long align)
& ~(align - 1)) + sizeof(struct vring_packed_desc_event) * 2;
}
+static void vring_unmap_one_packed(const struct vring_virtqueue *vq,
+ struct vring_packed_desc *desc)
+{
+ u16 flags;
+
+ if (!vring_use_dma_api(vq->vq.vdev))
+ return;
+
+ flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
+
+ if (flags & VRING_DESC_F_INDIRECT) {
+ dma_unmap_single(vring_dma_dev(vq),
+ virtio64_to_cpu(vq->vq.vdev, desc->addr),
+ virtio32_to_cpu(vq->vq.vdev, desc->len),
+ (flags & VRING_DESC_F_WRITE) ?
+ DMA_FROM_DEVICE : DMA_TO_DEVICE);
+ } else {
+ dma_unmap_page(vring_dma_dev(vq),
+ virtio64_to_cpu(vq->vq.vdev, desc->addr),
+ virtio32_to_cpu(vq->vq.vdev, desc->len),
+ (flags & VRING_DESC_F_WRITE) ?
+ DMA_FROM_DEVICE : DMA_TO_DEVICE);
+ }
+}
+
+static struct vring_packed_desc *alloc_indirect_packed(struct virtqueue *_vq,
+ unsigned int total_sg,
+ gfp_t gfp)
+{
+ struct vring_packed_desc *desc;
+
+ /*
+ * We require lowmem mappings for the descriptors because
+ * otherwise virt_to_phys will give us bogus addresses in the
+ * virtqueue.
+ */
+ gfp &= ~__GFP_HIGHMEM;
+
+ desc = kmalloc(total_sg * sizeof(struct vring_packed_desc), gfp);
+
+ return desc;
+}
+
static inline int virtqueue_add_packed(struct virtqueue *_vq,
struct scatterlist *sgs[],
unsigned int total_sg,
@@ -750,47 +802,419 @@ static inline int virtqueue_add_packed(struct virtqueue
*_vq,
void *ctx,
gfp_t gfp)
{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ struct vring_packed_desc *desc;
+ struct scatterlist *sg;
+ unsigned int i, n, descs_used, uninitialized_var(prev), err_idx;
+ __virtio16 uninitialized_var(head_flags), flags;
+ int head, wrap_counter;
+ bool indirect;
+
+ START_USE(vq);
+
+ BUG_ON(data == NULL);
+ BUG_ON(ctx && vq->indirect);
+
+ if (unlikely(vq->broken)) {
+ END_USE(vq);
+ return -EIO;
+ }
+
+#ifdef DEBUG
+ {
+ ktime_t now = ktime_get();
+
+ /* No kick or get, with .1 second between? Warn. */
+ if (vq->last_add_time_valid)
+ WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))
+ > 100);
+ vq->last_add_time = now;
+ vq->last_add_time_valid = true;
+ }
+#endif
+
+ BUG_ON(total_sg == 0);
+
+ head = vq->next_avail_idx;
+ wrap_counter = vq->wrap_counter;
+
+ if (virtqueue_use_indirect(_vq, total_sg))
+ desc = alloc_indirect_packed(_vq, total_sg, gfp);
+ else {
+ desc = NULL;
+ WARN_ON_ONCE(total_sg > vq->vring_packed.num &&
!vq->indirect);
+ }
+
+ if (desc) {
+ /* Use a single buffer which doesn't continue */
+ indirect = true;
+ /* Set up rest to use this indirect table. */
+ i = 0;
+ descs_used = 1;
+ } else {
+ indirect = false;
+ desc = vq->vring_packed.desc;
+ i = head;
+ descs_used = total_sg;
+ }
+
+ if (vq->vq.num_free < descs_used) {
+ pr_debug("Can't add buf len %i - avail = %i\n",
+ descs_used, vq->vq.num_free);
+ /* FIXME: for historical reasons, we force a notify here if
+ * there are outgoing parts to the buffer. Presumably the
+ * host should service the ring ASAP. */
+ if (out_sgs)
+ vq->notify(&vq->vq);
+ if (indirect)
+ kfree(desc);
+ END_USE(vq);
+ return -ENOSPC;
+ }
+
+ for (n = 0; n < out_sgs + in_sgs; n++) {
+ for (sg = sgs[n]; sg; sg = sg_next(sg)) {
+ dma_addr_t addr = vring_map_one_sg(vq, sg, n < out_sgs ?
+ DMA_TO_DEVICE : DMA_FROM_DEVICE);
+ if (vring_mapping_error(vq, addr))
+ goto unmap_release;
+
+ flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT |
+ (n < out_sgs ? 0 : VRING_DESC_F_WRITE) |
+ VRING_DESC_F_AVAIL(vq->wrap_counter) |
+ VRING_DESC_F_USED(!vq->wrap_counter));
+ if (!indirect && i == head)
+ head_flags = flags;
+ else
+ desc[i].flags = flags;
+
+ desc[i].addr = cpu_to_virtio64(_vq->vdev, addr);
+ desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
+ i++;
+ if (!indirect && i >= vq->vring_packed.num) {
+ i = 0;
+ vq->wrap_counter ^= 1;
+ }
+ }
+ }
+
+ prev = (i > 0 ? i : vq->vring_packed.num) - 1;
+ desc[prev].id = cpu_to_virtio32(_vq->vdev, head);
+
+ /* Last one doesn't continue. */
+ if (total_sg == 1)
+ head_flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);
+ else
+ desc[prev].flags &= cpu_to_virtio16(_vq->vdev,
+ ~VRING_DESC_F_NEXT);
+
+ if (indirect) {
+ /* Now that the indirect table is filled in, map it. */
+ dma_addr_t addr = vring_map_single(
+ vq, desc, total_sg * sizeof(struct vring_packed_desc),
+ DMA_TO_DEVICE);
+ if (vring_mapping_error(vq, addr))
+ goto unmap_release;
+
+ head_flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_INDIRECT |
+ VRING_DESC_F_AVAIL(wrap_counter) |
+ VRING_DESC_F_USED(!wrap_counter));
+ vq->vring_packed.desc[head].addr = cpu_to_virtio64(_vq->vdev,
+ addr);
+ vq->vring_packed.desc[head].len = cpu_to_virtio32(_vq->vdev,
+ total_sg * sizeof(struct vring_packed_desc));
+ vq->vring_packed.desc[head].id = cpu_to_virtio32(_vq->vdev,
+ head);
+ }
+
+ /* We're using some buffers from the free list. */
+ vq->vq.num_free -= descs_used;
+
+ /* Update free pointer */
+ if (indirect) {
+ n = head + 1;
+ if (n >= vq->vring_packed.num) {
+ n = 0;
+ vq->wrap_counter ^= 1;
+ }
+ vq->next_avail_idx = n;
+ } else
+ vq->next_avail_idx = i;
+
+ /* Store token and indirect buffer state. */
+ vq->desc_state[head].num = descs_used;
+ vq->desc_state[head].data = data;
+ if (indirect)
+ vq->desc_state[head].indir_desc = desc;
+ else
+ vq->desc_state[head].indir_desc = ctx;
+
+ /* A driver MUST NOT make the first descriptor in the list
+ * available before all subsequent descriptors comprising
+ * the list are made available. */
+ virtio_wmb(vq->weak_barriers);
+ vq->vring_packed.desc[head].flags = head_flags;
+ vq->num_added += descs_used;
+
+ pr_debug("Added buffer head %i to %p\n", head, vq);
+ END_USE(vq);
+
+ return 0;
+
+unmap_release:
+ err_idx = i;
+ i = head;
+
+ for (n = 0; n < total_sg; n++) {
+ if (i == err_idx)
+ break;
+ vring_unmap_one_packed(vq, &desc[i]);
+ i++;
+ if (!indirect && i >= vq->vring_packed.num)
+ i = 0;
+ }
+
+ vq->wrap_counter = wrap_counter;
+
+ if (indirect)
+ kfree(desc);
+
+ END_USE(vq);
return -EIO;
}
static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq)
{
- return false;
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ u16 flags;
+ bool needs_kick;
+ u32 snapshot;
+
+ START_USE(vq);
+ /* We need to expose the new flags value before checking notification
+ * suppressions. */
+ virtio_mb(vq->weak_barriers);
+
+ snapshot = *(u32 *)vq->vring_packed.device;
+ flags = cpu_to_virtio16(_vq->vdev, snapshot >> 16) & 0x3;
+
+#ifdef DEBUG
+ if (vq->last_add_time_valid) {
+ WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
+ vq->last_add_time)) > 100);
+ }
+ vq->last_add_time_valid = false;
+#endif
+
+ needs_kick = (flags != VRING_EVENT_F_DISABLE);
+ END_USE(vq);
+ return needs_kick;
+}
+
+static void detach_buf_packed(struct vring_virtqueue *vq, unsigned int head,
+ void **ctx)
+{
+ struct vring_packed_desc *desc;
+ unsigned int i, j;
+
+ /* Clear data ptr. */
+ vq->desc_state[head].data = NULL;
+
+ i = head;
+
+ for (j = 0; j < vq->desc_state[head].num; j++) {
+ desc = &vq->vring_packed.desc[i];
+ vring_unmap_one_packed(vq, desc);
+ i++;
+ if (i >= vq->vring_packed.num)
+ i = 0;
+ }
+
+ vq->vq.num_free += vq->desc_state[head].num;
+
+ if (vq->indirect) {
+ u32 len;
+
+ /* Free the indirect table, if any, now that it's unmapped. */
+ desc = vq->desc_state[head].indir_desc;
+ if (!desc)
+ return;
+
+ len = virtio32_to_cpu(vq->vq.vdev,
+ vq->vring_packed.desc[head].len);
+
+ for (j = 0; j < len / sizeof(struct vring_packed_desc); j++)
+ vring_unmap_one_packed(vq, &desc[j]);
+
+ kfree(desc);
+ vq->desc_state[head].indir_desc = NULL;
+ } else if (ctx) {
+ *ctx = vq->desc_state[head].indir_desc;
+ }
}
static inline bool more_used_packed(const struct vring_virtqueue *vq)
{
- return false;
+ u16 last_used, flags;
+ bool avail, used;
+
+ if (vq->vq.num_free == vq->vring_packed.num)
+ return false;
+
+ last_used = vq->last_used_idx;
+ flags = virtio16_to_cpu(vq->vq.vdev,
+ vq->vring_packed.desc[last_used].flags);
+ avail = flags & VRING_DESC_F_AVAIL(1);
+ used = flags & VRING_DESC_F_USED(1);
+
+ return avail == used;
}
static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
unsigned int *len,
void **ctx)
{
- return NULL;
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ void *ret;
+ unsigned int i;
+ u16 last_used;
+
+ START_USE(vq);
+
+ if (unlikely(vq->broken)) {
+ END_USE(vq);
+ return NULL;
+ }
+
+ if (!more_used_packed(vq)) {
+ pr_debug("No more buffers in queue\n");
+ END_USE(vq);
+ return NULL;
+ }
+
+ /* Only get used elements after they have been exposed by host. */
+ virtio_rmb(vq->weak_barriers);
+
+ last_used = vq->last_used_idx;
+ i = virtio32_to_cpu(_vq->vdev, vq->vring_packed.desc[last_used].id);
+ *len = virtio32_to_cpu(_vq->vdev, vq->vring_packed.desc[last_used].len);
+
+ if (unlikely(i >= vq->vring_packed.num)) {
+ BAD_RING(vq, "id %u out of range\n", i);
+ return NULL;
+ }
+ if (unlikely(!vq->desc_state[i].data)) {
+ BAD_RING(vq, "id %u is not a head!\n", i);
+ return NULL;
+ }
+
+ /* detach_buf_packed clears data, so grab it now. */
+ ret = vq->desc_state[i].data;
+ detach_buf_packed(vq, i, ctx);
+
+ vq->last_used_idx += vq->desc_state[i].num;
+ if (vq->last_used_idx >= vq->vring_packed.num)
+ vq->last_used_idx -= vq->vring_packed.num;
+
+#ifdef DEBUG
+ vq->last_add_time_valid = false;
+#endif
+
+ END_USE(vq);
+ return ret;
}
static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+
+ if (vq->event_flags_shadow != VRING_EVENT_F_DISABLE) {
+ vq->event_flags_shadow = VRING_EVENT_F_DISABLE;
+ vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev,
+ vq->event_flags_shadow);
+ }
}
static unsigned virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq)
{
- return 0;
+ struct vring_virtqueue *vq = to_vvq(_vq);
+
+ START_USE(vq);
+
+ /* We optimistically turn back on interrupts, then check if there was
+ * more to do. */
+
+ if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) {
+ virtio_wmb(vq->weak_barriers);
+ vq->event_flags_shadow = VRING_EVENT_F_ENABLE;
+ vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev,
+ vq->event_flags_shadow);
+ }
+
+ END_USE(vq);
+ return vq->last_used_idx;
}
static bool virtqueue_poll_packed(struct virtqueue *_vq, unsigned
last_used_idx)
{
- return false;
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ bool avail, used;
+ u16 flags;
+
+ virtio_mb(vq->weak_barriers);
+ flags = virtio16_to_cpu(vq->vq.vdev,
+ vq->vring_packed.desc[last_used_idx].flags);
+ avail = flags & VRING_DESC_F_AVAIL(1);
+ used = flags & VRING_DESC_F_USED(1);
+ return avail == used;
}
static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq)
{
- return false;
+ struct vring_virtqueue *vq = to_vvq(_vq);
+
+ START_USE(vq);
+
+ /* We optimistically turn back on interrupts, then check if there was
+ * more to do. */
+
+ if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) {
+ virtio_wmb(vq->weak_barriers);
+ vq->event_flags_shadow = VRING_EVENT_F_ENABLE;
+ vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev,
+ vq->event_flags_shadow);
+ }
+
+ if (more_used_packed(vq)) {
+ END_USE(vq);
+ return false;
+ }
+
+ END_USE(vq);
+ return true;
}
static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ unsigned int i;
+ void *buf;
+
+ START_USE(vq);
+
+ for (i = 0; i < vq->vring_packed.num; i++) {
+ if (!vq->desc_state[i].data)
+ continue;
+ /* detach_buf clears data, so grab it now. */
+ buf = vq->desc_state[i].data;
+ detach_buf_packed(vq, i, NULL);
+ END_USE(vq);
+ return buf;
+ }
+ /* That should have freed everything. */
+ BUG_ON(vq->vq.num_free != vq->vring_packed.num);
+
+ END_USE(vq);
return NULL;
}
--
2.11.0
Tiwei Bie
2018-Apr-25 05:15 UTC
[RFC v3 4/5] virtio_ring: add event idx support in packed ring
This commit introduces the event idx support in packed
ring. This feature is temporarily disabled, because the
implementation in this patch may not work as expected,
and some further discussions on the implementation are
needed, e.g. do we have to check the wrap counter when
checking whether a kick is needed?
Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
---
drivers/virtio/virtio_ring.c | 53 ++++++++++++++++++++++++++++++++++++++++----
1 file changed, 49 insertions(+), 4 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 0181e93897be..b1039c2985b9 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -986,7 +986,7 @@ static inline int virtqueue_add_packed(struct virtqueue
*_vq,
static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- u16 flags;
+ u16 new, old, off_wrap, flags;
bool needs_kick;
u32 snapshot;
@@ -995,7 +995,12 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue
*_vq)
* suppressions. */
virtio_mb(vq->weak_barriers);
+ old = vq->next_avail_idx - vq->num_added;
+ new = vq->next_avail_idx;
+ vq->num_added = 0;
+
snapshot = *(u32 *)vq->vring_packed.device;
+ off_wrap = virtio16_to_cpu(_vq->vdev, snapshot & 0xffff);
flags = cpu_to_virtio16(_vq->vdev, snapshot >> 16) & 0x3;
#ifdef DEBUG
@@ -1006,7 +1011,10 @@ static bool virtqueue_kick_prepare_packed(struct
virtqueue *_vq)
vq->last_add_time_valid = false;
#endif
- needs_kick = (flags != VRING_EVENT_F_DISABLE);
+ if (flags == VRING_EVENT_F_DESC)
+ needs_kick = vring_need_event(off_wrap & ~(1<<15), new, old);
+ else
+ needs_kick = (flags != VRING_EVENT_F_DISABLE);
END_USE(vq);
return needs_kick;
}
@@ -1116,6 +1124,15 @@ static void *virtqueue_get_buf_ctx_packed(struct
virtqueue *_vq,
if (vq->last_used_idx >= vq->vring_packed.num)
vq->last_used_idx -= vq->vring_packed.num;
+ /* If we expect an interrupt for the next entry, tell host
+ * by writing event index and flush out the write before
+ * the read in the next get_buf call. */
+ if (vq->event_flags_shadow == VRING_EVENT_F_DESC)
+ virtio_store_mb(vq->weak_barriers,
+ &vq->vring_packed.driver->off_wrap,
+ cpu_to_virtio16(_vq->vdev, vq->last_used_idx |
+ (vq->wrap_counter << 15)));
+
#ifdef DEBUG
vq->last_add_time_valid = false;
#endif
@@ -1143,10 +1160,17 @@ static unsigned
virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq)
/* We optimistically turn back on interrupts, then check if there was
* more to do. */
+ /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
+ * either clear the flags bit or point the event index at the next
+ * entry. Always update the event index to keep code simple. */
+
+ vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev,
+ vq->last_used_idx | (vq->wrap_counter << 15));
if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) {
virtio_wmb(vq->weak_barriers);
- vq->event_flags_shadow = VRING_EVENT_F_ENABLE;
+ vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC :
+ VRING_EVENT_F_ENABLE;
vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev,
vq->event_flags_shadow);
}
@@ -1172,15 +1196,34 @@ static bool virtqueue_poll_packed(struct virtqueue *_vq,
unsigned last_used_idx)
static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
+ u16 bufs, used_idx, wrap_counter;
START_USE(vq);
/* We optimistically turn back on interrupts, then check if there was
* more to do. */
+ /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
+ * either clear the flags bit or point the event index at the next
+ * entry. Always update the event index to keep code simple. */
+
+ /* TODO: tune this threshold */
+ bufs = (u16)(vq->next_avail_idx - vq->last_used_idx) * 3 / 4;
+
+ used_idx = vq->last_used_idx + bufs;
+ wrap_counter = vq->wrap_counter;
+
+ if (used_idx >= vq->vring_packed.num) {
+ used_idx -= vq->vring_packed.num;
+ wrap_counter ^= 1;
+ }
+
+ vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev,
+ used_idx | (wrap_counter << 15));
if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) {
virtio_wmb(vq->weak_barriers);
- vq->event_flags_shadow = VRING_EVENT_F_ENABLE;
+ vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC :
+ VRING_EVENT_F_ENABLE;
vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev,
vq->event_flags_shadow);
}
@@ -1822,8 +1865,10 @@ void vring_transport_features(struct virtio_device *vdev)
switch (i) {
case VIRTIO_RING_F_INDIRECT_DESC:
break;
+#if 0
case VIRTIO_RING_F_EVENT_IDX:
break;
+#endif
case VIRTIO_F_VERSION_1:
break;
case VIRTIO_F_IOMMU_PLATFORM:
--
2.11.0
Signed-off-by: Tiwei Bie <tiwei.bie at intel.com> --- drivers/virtio/virtio_ring.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index b1039c2985b9..9a3d13e1e2ba 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1873,6 +1873,8 @@ void vring_transport_features(struct virtio_device *vdev) break; case VIRTIO_F_IOMMU_PLATFORM: break; + case VIRTIO_F_RING_PACKED: + break; default: /* We don't understand this bit. */ __virtio_clear_bit(vdev, i); -- 2.11.0
Jason Wang
2018-May-02 02:51 UTC
[RFC v3 4/5] virtio_ring: add event idx support in packed ring
On 2018?04?25? 13:15, Tiwei Bie wrote:> This commit introduces the event idx support in packed > ring. This feature is temporarily disabled, because the > implementation in this patch may not work as expected, > and some further discussions on the implementation are > needed, e.g. do we have to check the wrap counter when > checking whether a kick is needed? > > Signed-off-by: Tiwei Bie <tiwei.bie at intel.com> > --- > drivers/virtio/virtio_ring.c | 53 ++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 49 insertions(+), 4 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 0181e93897be..b1039c2985b9 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -986,7 +986,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > { > struct vring_virtqueue *vq = to_vvq(_vq); > - u16 flags; > + u16 new, old, off_wrap, flags; > bool needs_kick; > u32 snapshot; > > @@ -995,7 +995,12 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > * suppressions. */ > virtio_mb(vq->weak_barriers); > > + old = vq->next_avail_idx - vq->num_added; > + new = vq->next_avail_idx; > + vq->num_added = 0; > + > snapshot = *(u32 *)vq->vring_packed.device; > + off_wrap = virtio16_to_cpu(_vq->vdev, snapshot & 0xffff); > flags = cpu_to_virtio16(_vq->vdev, snapshot >> 16) & 0x3; > > #ifdef DEBUG > @@ -1006,7 +1011,10 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > vq->last_add_time_valid = false; > #endif > > - needs_kick = (flags != VRING_EVENT_F_DISABLE); > + if (flags == VRING_EVENT_F_DESC) > + needs_kick = vring_need_event(off_wrap & ~(1<<15), new, old);I wonder whether or not the math is correct. Both new and event are in the unit of descriptor ring size, but old looks not. Thanks> + else > + needs_kick = (flags != VRING_EVENT_F_DISABLE); > END_USE(vq); > return needs_kick; > } > @@ -1116,6 +1124,15 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > if (vq->last_used_idx >= vq->vring_packed.num) > vq->last_used_idx -= vq->vring_packed.num; > > + /* If we expect an interrupt for the next entry, tell host > + * by writing event index and flush out the write before > + * the read in the next get_buf call. */ > + if (vq->event_flags_shadow == VRING_EVENT_F_DESC) > + virtio_store_mb(vq->weak_barriers, > + &vq->vring_packed.driver->off_wrap, > + cpu_to_virtio16(_vq->vdev, vq->last_used_idx | > + (vq->wrap_counter << 15))); > + > #ifdef DEBUG > vq->last_add_time_valid = false; > #endif > @@ -1143,10 +1160,17 @@ static unsigned virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq) > > /* We optimistically turn back on interrupts, then check if there was > * more to do. */ > + /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to > + * either clear the flags bit or point the event index at the next > + * entry. Always update the event index to keep code simple. */ > + > + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, > + vq->last_used_idx | (vq->wrap_counter << 15)); > > if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { > virtio_wmb(vq->weak_barriers); > - vq->event_flags_shadow = VRING_EVENT_F_ENABLE; > + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : > + VRING_EVENT_F_ENABLE; > vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, > vq->event_flags_shadow); > } > @@ -1172,15 +1196,34 @@ static bool virtqueue_poll_packed(struct virtqueue *_vq, unsigned last_used_idx) > static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq) > { > struct vring_virtqueue *vq = to_vvq(_vq); > + u16 bufs, used_idx, wrap_counter; > > START_USE(vq); > > /* We optimistically turn back on interrupts, then check if there was > * more to do. */ > + /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to > + * either clear the flags bit or point the event index at the next > + * entry. Always update the event index to keep code simple. */ > + > + /* TODO: tune this threshold */ > + bufs = (u16)(vq->next_avail_idx - vq->last_used_idx) * 3 / 4; > + > + used_idx = vq->last_used_idx + bufs; > + wrap_counter = vq->wrap_counter; > + > + if (used_idx >= vq->vring_packed.num) { > + used_idx -= vq->vring_packed.num; > + wrap_counter ^= 1; > + } > + > + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, > + used_idx | (wrap_counter << 15)); > > if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { > virtio_wmb(vq->weak_barriers); > - vq->event_flags_shadow = VRING_EVENT_F_ENABLE; > + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : > + VRING_EVENT_F_ENABLE; > vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, > vq->event_flags_shadow); > } > @@ -1822,8 +1865,10 @@ void vring_transport_features(struct virtio_device *vdev) > switch (i) { > case VIRTIO_RING_F_INDIRECT_DESC: > break; > +#if 0 > case VIRTIO_RING_F_EVENT_IDX: > break; > +#endif > case VIRTIO_F_VERSION_1: > break; > case VIRTIO_F_IOMMU_PLATFORM:
On 2018?04?25? 13:15, Tiwei Bie wrote:> Hello everyone, > > This RFC implements packed ring support in virtio driver. > > Some simple functional tests have been done with Jason's > packed ring implementation in vhost: > > https://lkml.org/lkml/2018/4/23/12 > > Both of ping and netperf worked as expected (with EVENT_IDX > disabled). But there are below known issues: > > 1. Reloading the guest driver will break the Tx/Rx;It looks like the reason is we don't sync wrap counter information between host and qemu through VHOST_SET/GET_VRING_BASE. And both vhost and qemu need to do this through encoding warp counters to higher bits of vhost_vring_state.num, Thanks
On 2018?04?25? 13:15, Tiwei Bie wrote:> + /* We're using some buffers from the free list. */ > + vq->vq.num_free -= descs_used; > + > + /* Update free pointer */ > + if (indirect) { > + n = head + 1; > + if (n >= vq->vring_packed.num) { > + n = 0; > + vq->wrap_counter ^= 1; > + } > + vq->next_avail_idx = n; > + } else > + vq->next_avail_idx = i;During testing zerocopy (out of order completion), I found driver may submit two identical buffer id to vhost. So the above code may not work well. Consider the case that driver adds 3 buffer and virtqueue size is 8. a) id = 0,count = 2,next_avail = 2 b) id = 2,count = 4,next_avail = 2 c) id = 4,count = 2,next_avail = 0 if packet b is done before packet a, driver may think buffer id 0 is available and try to use it if even if the real buffer 0 was not done. Thanks
Jason Wang
2018-May-16 05:01 UTC
[RFC v3 4/5] virtio_ring: add event idx support in packed ring
On 2018?04?25? 13:15, Tiwei Bie wrote:> This commit introduces the event idx support in packed > ring. This feature is temporarily disabled, because the > implementation in this patch may not work as expected, > and some further discussions on the implementation are > needed, e.g. do we have to check the wrap counter when > checking whether a kick is needed? > > Signed-off-by: Tiwei Bie <tiwei.bie at intel.com> > --- > drivers/virtio/virtio_ring.c | 53 ++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 49 insertions(+), 4 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 0181e93897be..b1039c2985b9 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -986,7 +986,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > { > struct vring_virtqueue *vq = to_vvq(_vq); > - u16 flags; > + u16 new, old, off_wrap, flags; > bool needs_kick; > u32 snapshot; > > @@ -995,7 +995,12 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > * suppressions. */ > virtio_mb(vq->weak_barriers); > > + old = vq->next_avail_idx - vq->num_added; > + new = vq->next_avail_idx; > + vq->num_added = 0; > + > snapshot = *(u32 *)vq->vring_packed.device; > + off_wrap = virtio16_to_cpu(_vq->vdev, snapshot & 0xffff); > flags = cpu_to_virtio16(_vq->vdev, snapshot >> 16) & 0x3; > > #ifdef DEBUG > @@ -1006,7 +1011,10 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > vq->last_add_time_valid = false; > #endif > > - needs_kick = (flags != VRING_EVENT_F_DISABLE); > + if (flags == VRING_EVENT_F_DESC) > + needs_kick = vring_need_event(off_wrap & ~(1<<15), new, old); > + else > + needs_kick = (flags != VRING_EVENT_F_DISABLE); > END_USE(vq); > return needs_kick; > } > @@ -1116,6 +1124,15 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > if (vq->last_used_idx >= vq->vring_packed.num) > vq->last_used_idx -= vq->vring_packed.num; > > + /* If we expect an interrupt for the next entry, tell host > + * by writing event index and flush out the write before > + * the read in the next get_buf call. */ > + if (vq->event_flags_shadow == VRING_EVENT_F_DESC) > + virtio_store_mb(vq->weak_barriers, > + &vq->vring_packed.driver->off_wrap, > + cpu_to_virtio16(_vq->vdev, vq->last_used_idx | > + (vq->wrap_counter << 15))); > + > #ifdef DEBUG > vq->last_add_time_valid = false; > #endif > @@ -1143,10 +1160,17 @@ static unsigned virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq) > > /* We optimistically turn back on interrupts, then check if there was > * more to do. */ > + /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to > + * either clear the flags bit or point the event index at the next > + * entry. Always update the event index to keep code simple. */ > + > + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, > + vq->last_used_idx | (vq->wrap_counter << 15));Using vq->wrap_counter seems not correct, what we need is the warp counter for the last_used_idx not next_avail_idx. And I think there's even no need to bother with event idx here, how about just set VRING_EVENT_F_ENABLE?> > if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { > virtio_wmb(vq->weak_barriers); > - vq->event_flags_shadow = VRING_EVENT_F_ENABLE; > + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : > + VRING_EVENT_F_ENABLE; > vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, > vq->event_flags_shadow); > } > @@ -1172,15 +1196,34 @@ static bool virtqueue_poll_packed(struct virtqueue *_vq, unsigned last_used_idx) > static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq) > { > struct vring_virtqueue *vq = to_vvq(_vq); > + u16 bufs, used_idx, wrap_counter; > > START_USE(vq); > > /* We optimistically turn back on interrupts, then check if there was > * more to do. */ > + /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to > + * either clear the flags bit or point the event index at the next > + * entry. Always update the event index to keep code simple. */ > + > + /* TODO: tune this threshold */ > + bufs = (u16)(vq->next_avail_idx - vq->last_used_idx) * 3 / 4;bufs could be more than vq->num here, is this intended?> + > + used_idx = vq->last_used_idx + bufs; > + wrap_counter = vq->wrap_counter; > + > + if (used_idx >= vq->vring_packed.num) { > + used_idx -= vq->vring_packed.num; > + wrap_counter ^= 1;When used_idx is greater or equal vq->num, there's no need to flip warp_counter bit since it should match next_avail_idx. And we need also care about the case when next_avail wraps but used_idx not. so we probaly need: else if (vq->next_avail_idx < used_idx) { ??? wrap_counter ^= 1; } I think maybe it's time to add some sample codes in the spec to avoid duplicating the efforts(bugs). Thanks> + } > + > + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, > + used_idx | (wrap_counter << 15)); > > if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { > virtio_wmb(vq->weak_barriers); > - vq->event_flags_shadow = VRING_EVENT_F_ENABLE; > + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : > + VRING_EVENT_F_ENABLE; > vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, > vq->event_flags_shadow); > } > @@ -1822,8 +1865,10 @@ void vring_transport_features(struct virtio_device *vdev) > switch (i) { > case VIRTIO_RING_F_INDIRECT_DESC: > break; > +#if 0 > case VIRTIO_RING_F_EVENT_IDX: > break; > +#endif > case VIRTIO_F_VERSION_1: > break; > case VIRTIO_F_IOMMU_PLATFORM:
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