/*
*
* 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;
virt_mb();
}
u32 hv_end_read(struct hv_ring_buffer_info *rbi)
{
rbi->ring_buffer->interrupt_mask = 0;
virt_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.
*/
return hv_get_bytes_to_read(rbi);
}
/*
* 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)
{
virt_mb();
if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
return false;
/* check interrupt_mask before read_index */
virt_rmb();
/*
* This is the only case we need to signal when the
* ring transitions from being empty to non-empty.
*/
if (old_write == READ_ONCE(rbi->ring_buffer->read_index))
return true;
return false;
}
/* 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;
}
/* 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;
}
/* 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;
}
/*
* 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;
}
/* 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;
ring_info->priv_read_index = next_read_location;
}
/* 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;
}
/* 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;
}
/*
* 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;
}
/*
* 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;
}
/* 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;
}
}
/* 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;
}
/* Cleanup the ring buffer. */
void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
{
}
/* 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, bool lock)
{
int i = 0;
u32 bytes_avail_towrite;
u32 totalbytes_towrite = 0;
u32 next_write_location;
u32 old_write;
u64 prev_indices = 0;
unsigned long flags = 0;
for (i = 0; i < kv_count; i++)
totalbytes_towrite += kv_list[i].iov_len;
totalbytes_towrite += sizeof(u64);
if (lock)
spin_lock_irqsave(&outring_info->ring_lock, flags);
bytes_avail_towrite = hv_get_bytes_to_write(outring_info);
/*
* 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) {
if (lock)
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 */
virt_mb();
/* Now, update the write location */
hv_set_next_write_location(outring_info, next_write_location);
if (lock)
spin_unlock_irqrestore(&outring_info->ring_lock, flags);
*signal = hv_need_to_signal(old_write, outring_info);
return 0;
}
int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
void *buffer, u32 buflen, u32 *buffer_actual_len,
u64 *requestid, bool *signal, bool raw)
{
u32 bytes_avail_toread;
u32 next_read_location = 0;
u64 prev_indices = 0;
struct vmpacket_descriptor desc;
u32 offset;
u32 packetlen;
int ret = 0;
if (buflen <= 0)
return -EINVAL;
*buffer_actual_len = 0;
*requestid = 0;
bytes_avail_toread = hv_get_bytes_to_read(inring_info);
/* Make sure there is something to read */
if (bytes_avail_toread < sizeof(desc)) {
/*
* No error is set when there is even no header, drivers are
* supposed to analyze buffer_actual_len.
*/
return ret;
}
next_read_location = hv_get_next_read_location(inring_info);
next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc,
sizeof(desc),
next_read_location);
offset = raw ? 0 : (desc.offset8 << 3);
packetlen = (desc.len8 << 3) - offset;
*buffer_actual_len = packetlen;
*requestid = desc.trans_id;
if (bytes_avail_toread < packetlen + offset)
return -EAGAIN;
if (packetlen > buflen)
return -ENOBUFS;
next_read_location =
hv_get_next_readlocation_withoffset(inring_info, offset);
next_read_location = hv_copyfrom_ringbuffer(inring_info,
buffer,
packetlen,
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.
*/
virt_mb();
/* Update the read index */
hv_set_next_read_location(inring_info, next_read_location);
*signal = hv_need_to_signal_on_read(inring_info);
return ret;
}
