--- /dev/null
+/*
+ *
+ * Copyright (c) 2009, Microsoft Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+ * Place - Suite 330, Boston, MA 02111-1307 USA.
+ *
+ * Authors:
+ * Haiyang Zhang <haiyangz@microsoft.com>
+ * Hank Janssen <hjanssen@microsoft.com>
+ * K. Y. Srinivasan <kys@microsoft.com>
+ *
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/hyperv.h>
+#include <linux/uio.h>
+
+#include "hyperv_vmbus.h"
+
+void hv_begin_read(struct hv_ring_buffer_info *rbi)
+{
+ rbi->ring_buffer->interrupt_mask = 1;
+ mb();
+}
+
+u32 hv_end_read(struct hv_ring_buffer_info *rbi)
+{
+ u32 read;
+ u32 write;
+
+ rbi->ring_buffer->interrupt_mask = 0;
+ mb();
+
+ /*
+ * Now check to see if the ring buffer is still empty.
+ * If it is not, we raced and we need to process new
+ * incoming messages.
+ */
+ hv_get_ringbuffer_availbytes(rbi, &read, &write);
+
+ return read;
+}
+
+/*
+ * When we write to the ring buffer, check if the host needs to
+ * be signaled. Here is the details of this protocol:
+ *
+ * 1. The host guarantees that while it is draining the
+ * ring buffer, it will set the interrupt_mask to
+ * indicate it does not need to be interrupted when
+ * new data is placed.
+ *
+ * 2. The host guarantees that it will completely drain
+ * the ring buffer before exiting the read loop. Further,
+ * once the ring buffer is empty, it will clear the
+ * interrupt_mask and re-check to see if new data has
+ * arrived.
+ */
+
+static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
+{
+ mb();
+ if (rbi->ring_buffer->interrupt_mask)
+ return false;
+
+ /* check interrupt_mask before read_index */
+ rmb();
+ /*
+ * This is the only case we need to signal when the
+ * ring transitions from being empty to non-empty.
+ */
+ if (old_write == rbi->ring_buffer->read_index)
+ return true;
+
+ return false;
+}
+
+/*
+ * To optimize the flow management on the send-side,
+ * when the sender is blocked because of lack of
+ * sufficient space in the ring buffer, potential the
+ * consumer of the ring buffer can signal the producer.
+ * This is controlled by the following parameters:
+ *
+ * 1. pending_send_sz: This is the size in bytes that the
+ * producer is trying to send.
+ * 2. The feature bit feat_pending_send_sz set to indicate if
+ * the consumer of the ring will signal when the ring
+ * state transitions from being full to a state where
+ * there is room for the producer to send the pending packet.
+ */
+
+static bool hv_need_to_signal_on_read(u32 old_rd,
+ struct hv_ring_buffer_info *rbi)
+{
+ u32 prev_write_sz;
+ u32 cur_write_sz;
+ u32 r_size;
+ u32 write_loc = rbi->ring_buffer->write_index;
+ u32 read_loc = rbi->ring_buffer->read_index;
+ u32 pending_sz = rbi->ring_buffer->pending_send_sz;
+
+ /*
+ * If the other end is not blocked on write don't bother.
+ */
+ if (pending_sz == 0)
+ return false;
+
+ r_size = rbi->ring_datasize;
+ cur_write_sz = write_loc >= read_loc ? r_size - (write_loc - read_loc) :
+ read_loc - write_loc;
+
+ prev_write_sz = write_loc >= old_rd ? r_size - (write_loc - old_rd) :
+ old_rd - write_loc;
+
+
+ if ((prev_write_sz < pending_sz) && (cur_write_sz >= pending_sz))
+ return true;
+
+ return false;
+}
+
+/*
+ * hv_get_next_write_location()
+ *
+ * Get the next write location for the specified ring buffer
+ *
+ */
+static inline u32
+hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
+{
+ u32 next = ring_info->ring_buffer->write_index;
+
+ return next;
+}
+
+/*
+ * hv_set_next_write_location()
+ *
+ * Set the next write location for the specified ring buffer
+ *
+ */
+static inline void
+hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
+ u32 next_write_location)
+{
+ ring_info->ring_buffer->write_index = next_write_location;
+}
+
+/*
+ * hv_get_next_read_location()
+ *
+ * Get the next read location for the specified ring buffer
+ */
+static inline u32
+hv_get_next_read_location(struct hv_ring_buffer_info *ring_info)
+{
+ u32 next = ring_info->ring_buffer->read_index;
+
+ return next;
+}
+
+/*
+ * hv_get_next_readlocation_withoffset()
+ *
+ * Get the next read location + offset for the specified ring buffer.
+ * This allows the caller to skip
+ */
+static inline u32
+hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
+ u32 offset)
+{
+ u32 next = ring_info->ring_buffer->read_index;
+
+ next += offset;
+ next %= ring_info->ring_datasize;
+
+ return next;
+}
+
+/*
+ *
+ * hv_set_next_read_location()
+ *
+ * Set the next read location for the specified ring buffer
+ *
+ */
+static inline void
+hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
+ u32 next_read_location)
+{
+ ring_info->ring_buffer->read_index = next_read_location;
+}
+
+
+/*
+ *
+ * hv_get_ring_buffer()
+ *
+ * Get the start of the ring buffer
+ */
+static inline void *
+hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
+{
+ return (void *)ring_info->ring_buffer->buffer;
+}
+
+
+/*
+ *
+ * hv_get_ring_buffersize()
+ *
+ * Get the size of the ring buffer
+ */
+static inline u32
+hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
+{
+ return ring_info->ring_datasize;
+}
+
+/*
+ *
+ * hv_get_ring_bufferindices()
+ *
+ * Get the read and write indices as u64 of the specified ring buffer
+ *
+ */
+static inline u64
+hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
+{
+ return (u64)ring_info->ring_buffer->write_index << 32;
+}
+
+/*
+ *
+ * hv_copyfrom_ringbuffer()
+ *
+ * Helper routine to copy to source from ring buffer.
+ * Assume there is enough room. Handles wrap-around in src case only!!
+ *
+ */
+static u32 hv_copyfrom_ringbuffer(
+ struct hv_ring_buffer_info *ring_info,
+ void *dest,
+ u32 destlen,
+ u32 start_read_offset)
+{
+ void *ring_buffer = hv_get_ring_buffer(ring_info);
+ u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
+
+ u32 frag_len;
+
+ /* wrap-around detected at the src */
+ if (destlen > ring_buffer_size - start_read_offset) {
+ frag_len = ring_buffer_size - start_read_offset;
+
+ memcpy(dest, ring_buffer + start_read_offset, frag_len);
+ memcpy(dest + frag_len, ring_buffer, destlen - frag_len);
+ } else
+
+ memcpy(dest, ring_buffer + start_read_offset, destlen);
+
+
+ start_read_offset += destlen;
+ start_read_offset %= ring_buffer_size;
+
+ return start_read_offset;
+}
+
+
+/*
+ *
+ * hv_copyto_ringbuffer()
+ *
+ * Helper routine to copy from source to ring buffer.
+ * Assume there is enough room. Handles wrap-around in dest case only!!
+ *
+ */
+static u32 hv_copyto_ringbuffer(
+ struct hv_ring_buffer_info *ring_info,
+ u32 start_write_offset,
+ void *src,
+ u32 srclen)
+{
+ void *ring_buffer = hv_get_ring_buffer(ring_info);
+ u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
+ u32 frag_len;
+
+ /* wrap-around detected! */
+ if (srclen > ring_buffer_size - start_write_offset) {
+ frag_len = ring_buffer_size - start_write_offset;
+ memcpy(ring_buffer + start_write_offset, src, frag_len);
+ memcpy(ring_buffer, src + frag_len, srclen - frag_len);
+ } else
+ memcpy(ring_buffer + start_write_offset, src, srclen);
+
+ start_write_offset += srclen;
+ start_write_offset %= ring_buffer_size;
+
+ return start_write_offset;
+}
+
+/*
+ *
+ * hv_ringbuffer_get_debuginfo()
+ *
+ * Get various debug metrics for the specified ring buffer
+ *
+ */
+void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
+ struct hv_ring_buffer_debug_info *debug_info)
+{
+ u32 bytes_avail_towrite;
+ u32 bytes_avail_toread;
+
+ if (ring_info->ring_buffer) {
+ hv_get_ringbuffer_availbytes(ring_info,
+ &bytes_avail_toread,
+ &bytes_avail_towrite);
+
+ debug_info->bytes_avail_toread = bytes_avail_toread;
+ debug_info->bytes_avail_towrite = bytes_avail_towrite;
+ debug_info->current_read_index =
+ ring_info->ring_buffer->read_index;
+ debug_info->current_write_index =
+ ring_info->ring_buffer->write_index;
+ debug_info->current_interrupt_mask =
+ ring_info->ring_buffer->interrupt_mask;
+ }
+}
+
+/*
+ *
+ * hv_ringbuffer_init()
+ *
+ *Initialize the ring buffer
+ *
+ */
+int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
+ void *buffer, u32 buflen)
+{
+ if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
+ return -EINVAL;
+
+ memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
+
+ ring_info->ring_buffer = (struct hv_ring_buffer *)buffer;
+ ring_info->ring_buffer->read_index =
+ ring_info->ring_buffer->write_index = 0;
+
+ /*
+ * Set the feature bit for enabling flow control.
+ */
+ ring_info->ring_buffer->feature_bits.value = 1;
+
+ ring_info->ring_size = buflen;
+ ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer);
+
+ spin_lock_init(&ring_info->ring_lock);
+
+ return 0;
+}
+
+/*
+ *
+ * hv_ringbuffer_cleanup()
+ *
+ * Cleanup the ring buffer
+ *
+ */
+void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
+{
+}
+
+/*
+ *
+ * hv_ringbuffer_write()
+ *
+ * Write to the ring buffer
+ *
+ */
+int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
+ struct kvec *kv_list, u32 kv_count, bool *signal)
+{
+ int i = 0;
+ u32 bytes_avail_towrite;
+ u32 bytes_avail_toread;
+ u32 totalbytes_towrite = 0;
+
+ u32 next_write_location;
+ u32 old_write;
+ u64 prev_indices = 0;
+ unsigned long flags;
+
+ for (i = 0; i < kv_count; i++)
+ totalbytes_towrite += kv_list[i].iov_len;
+
+ totalbytes_towrite += sizeof(u64);
+
+ spin_lock_irqsave(&outring_info->ring_lock, flags);
+
+ hv_get_ringbuffer_availbytes(outring_info,
+ &bytes_avail_toread,
+ &bytes_avail_towrite);
+
+
+ /* If there is only room for the packet, assume it is full. */
+ /* Otherwise, the next time around, we think the ring buffer */
+ /* is empty since the read index == write index */
+ if (bytes_avail_towrite <= totalbytes_towrite) {
+ spin_unlock_irqrestore(&outring_info->ring_lock, flags);
+ return -EAGAIN;
+ }
+
+ /* Write to the ring buffer */
+ next_write_location = hv_get_next_write_location(outring_info);
+
+ old_write = next_write_location;
+
+ for (i = 0; i < kv_count; i++) {
+ next_write_location = hv_copyto_ringbuffer(outring_info,
+ next_write_location,
+ kv_list[i].iov_base,
+ kv_list[i].iov_len);
+ }
+
+ /* Set previous packet start */
+ prev_indices = hv_get_ring_bufferindices(outring_info);
+
+ next_write_location = hv_copyto_ringbuffer(outring_info,
+ next_write_location,
+ &prev_indices,
+ sizeof(u64));
+
+ /* Issue a full memory barrier before updating the write index */
+ mb();
+
+ /* Now, update the write location */
+ hv_set_next_write_location(outring_info, next_write_location);
+
+
+ spin_unlock_irqrestore(&outring_info->ring_lock, flags);
+
+ *signal = hv_need_to_signal(old_write, outring_info);
+ return 0;
+}
+
+
+/*
+ *
+ * hv_ringbuffer_peek()
+ *
+ * Read without advancing the read index
+ *
+ */
+int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info,
+ void *Buffer, u32 buflen)
+{
+ u32 bytes_avail_towrite;
+ u32 bytes_avail_toread;
+ u32 next_read_location = 0;
+ unsigned long flags;
+
+ spin_lock_irqsave(&Inring_info->ring_lock, flags);
+
+ hv_get_ringbuffer_availbytes(Inring_info,
+ &bytes_avail_toread,
+ &bytes_avail_towrite);
+
+ /* Make sure there is something to read */
+ if (bytes_avail_toread < buflen) {
+
+ spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
+
+ return -EAGAIN;
+ }
+
+ /* Convert to byte offset */
+ next_read_location = hv_get_next_read_location(Inring_info);
+
+ next_read_location = hv_copyfrom_ringbuffer(Inring_info,
+ Buffer,
+ buflen,
+ next_read_location);
+
+ spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
+
+ return 0;
+}
+
+
+/*
+ *
+ * hv_ringbuffer_read()
+ *
+ * Read and advance the read index
+ *
+ */
+int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
+ u32 buflen, u32 offset, bool *signal)
+{
+ u32 bytes_avail_towrite;
+ u32 bytes_avail_toread;
+ u32 next_read_location = 0;
+ u64 prev_indices = 0;
+ unsigned long flags;
+ u32 old_read;
+
+ if (buflen <= 0)
+ return -EINVAL;
+
+ spin_lock_irqsave(&inring_info->ring_lock, flags);
+
+ hv_get_ringbuffer_availbytes(inring_info,
+ &bytes_avail_toread,
+ &bytes_avail_towrite);
+
+ old_read = bytes_avail_toread;
+
+ /* Make sure there is something to read */
+ if (bytes_avail_toread < buflen) {
+ spin_unlock_irqrestore(&inring_info->ring_lock, flags);
+
+ return -EAGAIN;
+ }
+
+ next_read_location =
+ hv_get_next_readlocation_withoffset(inring_info, offset);
+
+ next_read_location = hv_copyfrom_ringbuffer(inring_info,
+ buffer,
+ buflen,
+ next_read_location);
+
+ next_read_location = hv_copyfrom_ringbuffer(inring_info,
+ &prev_indices,
+ sizeof(u64),
+ next_read_location);
+
+ /* Make sure all reads are done before we update the read index since */
+ /* the writer may start writing to the read area once the read index */
+ /*is updated */
+ mb();
+
+ /* Update the read index */
+ hv_set_next_read_location(inring_info, next_read_location);
+
+ spin_unlock_irqrestore(&inring_info->ring_lock, flags);
+
+ *signal = hv_need_to_signal_on_read(old_read, inring_info);
+
+ return 0;
+}
Code Review / kvmfornfv.git / blobdiff