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/*
*
* 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)
{
smp_mb();
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
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