linux/drivers/hv/ring_buffer.c
K. Y. Srinivasan c2b8e5202c Drivers: hv: Implement flow management on the send side
Implement flow management on the send side. When the sender is blocked, the reader
can potentially signal the sender to indicate there is now room to send.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-01-17 11:41:49 -08:00

562 lines
13 KiB
C

/*
*
* 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 "hyperv_vmbus.h"
void hv_begin_read(struct hv_ring_buffer_info *rbi)
{
rbi->ring_buffer->interrupt_mask = 1;
smp_mb();
}
u32 hv_end_read(struct hv_ring_buffer_info *rbi)
{
u32 read;
u32 write;
rbi->ring_buffer->interrupt_mask = 0;
smp_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)
{
if (rbi->ring_buffer->interrupt_mask)
return false;
/*
* 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;
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 scatterlist *sglist, u32 sgcount, bool *signal)
{
int i = 0;
u32 bytes_avail_towrite;
u32 bytes_avail_toread;
u32 totalbytes_towrite = 0;
struct scatterlist *sg;
u32 next_write_location;
u32 old_write;
u64 prev_indices = 0;
unsigned long flags;
for_each_sg(sglist, sg, sgcount, i)
{
totalbytes_towrite += sg->length;
}
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_each_sg(sglist, sg, sgcount, i)
{
next_write_location = hv_copyto_ringbuffer(outring_info,
next_write_location,
sg_virt(sg),
sg->length);
}
/* 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 */
smp_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 */
smp_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;
}