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![K. Y. Srinivasan](/assets/img/avatar_default.png)
Implement APIs for in-place consumption of vmbus packets. Currently, each packet is copied and processed one at a time and as part of processing each packet we potentially may signal the host (if it is waiting for room to produce a packet). These APIs help batched in-place processing of vmbus packets. We also optimize host signaling by having a separate API to signal the end of in-place consumption. With netvsc using these APIs, on an iperf run on average I see about 20X reduction in checks to signal the host. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
404 lines
11 KiB
C
404 lines
11 KiB
C
/*
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*
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* Copyright (c) 2009, Microsoft Corporation.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 59 Temple
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* Place - Suite 330, Boston, MA 02111-1307 USA.
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*
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* Authors:
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* Haiyang Zhang <haiyangz@microsoft.com>
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* Hank Janssen <hjanssen@microsoft.com>
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* K. Y. Srinivasan <kys@microsoft.com>
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*
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/hyperv.h>
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#include <linux/uio.h>
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#include "hyperv_vmbus.h"
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void hv_begin_read(struct hv_ring_buffer_info *rbi)
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{
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rbi->ring_buffer->interrupt_mask = 1;
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virt_mb();
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}
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u32 hv_end_read(struct hv_ring_buffer_info *rbi)
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{
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rbi->ring_buffer->interrupt_mask = 0;
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virt_mb();
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/*
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* Now check to see if the ring buffer is still empty.
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* If it is not, we raced and we need to process new
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* incoming messages.
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*/
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return hv_get_bytes_to_read(rbi);
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}
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/*
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* When we write to the ring buffer, check if the host needs to
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* be signaled. Here is the details of this protocol:
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*
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* 1. The host guarantees that while it is draining the
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* ring buffer, it will set the interrupt_mask to
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* indicate it does not need to be interrupted when
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* new data is placed.
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*
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* 2. The host guarantees that it will completely drain
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* the ring buffer before exiting the read loop. Further,
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* once the ring buffer is empty, it will clear the
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* interrupt_mask and re-check to see if new data has
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* arrived.
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*/
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static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
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{
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virt_mb();
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if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
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return false;
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/* check interrupt_mask before read_index */
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virt_rmb();
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/*
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* This is the only case we need to signal when the
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* ring transitions from being empty to non-empty.
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*/
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if (old_write == READ_ONCE(rbi->ring_buffer->read_index))
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return true;
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return false;
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}
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/* Get the next write location for the specified ring buffer. */
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static inline u32
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hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
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{
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u32 next = ring_info->ring_buffer->write_index;
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return next;
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}
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/* Set the next write location for the specified ring buffer. */
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static inline void
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hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
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u32 next_write_location)
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{
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ring_info->ring_buffer->write_index = next_write_location;
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}
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/* Get the next read location for the specified ring buffer. */
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static inline u32
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hv_get_next_read_location(struct hv_ring_buffer_info *ring_info)
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{
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u32 next = ring_info->ring_buffer->read_index;
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return next;
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}
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/*
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* Get the next read location + offset for the specified ring buffer.
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* This allows the caller to skip.
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*/
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static inline u32
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hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
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u32 offset)
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{
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u32 next = ring_info->ring_buffer->read_index;
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next += offset;
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next %= ring_info->ring_datasize;
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return next;
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}
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/* Set the next read location for the specified ring buffer. */
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static inline void
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hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
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u32 next_read_location)
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{
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ring_info->ring_buffer->read_index = next_read_location;
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ring_info->priv_read_index = next_read_location;
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}
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/* Get the size of the ring buffer. */
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static inline u32
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hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
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{
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return ring_info->ring_datasize;
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}
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/* Get the read and write indices as u64 of the specified ring buffer. */
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static inline u64
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hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
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{
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return (u64)ring_info->ring_buffer->write_index << 32;
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}
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/*
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* Helper routine to copy to source from ring buffer.
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* Assume there is enough room. Handles wrap-around in src case only!!
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*/
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static u32 hv_copyfrom_ringbuffer(
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struct hv_ring_buffer_info *ring_info,
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void *dest,
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u32 destlen,
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u32 start_read_offset)
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{
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void *ring_buffer = hv_get_ring_buffer(ring_info);
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u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
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u32 frag_len;
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/* wrap-around detected at the src */
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if (destlen > ring_buffer_size - start_read_offset) {
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frag_len = ring_buffer_size - start_read_offset;
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memcpy(dest, ring_buffer + start_read_offset, frag_len);
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memcpy(dest + frag_len, ring_buffer, destlen - frag_len);
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} else
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memcpy(dest, ring_buffer + start_read_offset, destlen);
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start_read_offset += destlen;
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start_read_offset %= ring_buffer_size;
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return start_read_offset;
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}
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/*
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* Helper routine to copy from source to ring buffer.
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* Assume there is enough room. Handles wrap-around in dest case only!!
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*/
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static u32 hv_copyto_ringbuffer(
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struct hv_ring_buffer_info *ring_info,
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u32 start_write_offset,
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void *src,
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u32 srclen)
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{
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void *ring_buffer = hv_get_ring_buffer(ring_info);
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u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
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u32 frag_len;
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/* wrap-around detected! */
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if (srclen > ring_buffer_size - start_write_offset) {
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frag_len = ring_buffer_size - start_write_offset;
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memcpy(ring_buffer + start_write_offset, src, frag_len);
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memcpy(ring_buffer, src + frag_len, srclen - frag_len);
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} else
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memcpy(ring_buffer + start_write_offset, src, srclen);
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start_write_offset += srclen;
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start_write_offset %= ring_buffer_size;
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return start_write_offset;
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}
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/* Get various debug metrics for the specified ring buffer. */
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void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
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struct hv_ring_buffer_debug_info *debug_info)
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{
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u32 bytes_avail_towrite;
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u32 bytes_avail_toread;
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if (ring_info->ring_buffer) {
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hv_get_ringbuffer_availbytes(ring_info,
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&bytes_avail_toread,
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&bytes_avail_towrite);
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debug_info->bytes_avail_toread = bytes_avail_toread;
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debug_info->bytes_avail_towrite = bytes_avail_towrite;
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debug_info->current_read_index =
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ring_info->ring_buffer->read_index;
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debug_info->current_write_index =
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ring_info->ring_buffer->write_index;
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debug_info->current_interrupt_mask =
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ring_info->ring_buffer->interrupt_mask;
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}
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}
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/* Initialize the ring buffer. */
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int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
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void *buffer, u32 buflen)
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{
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if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
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return -EINVAL;
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memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
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ring_info->ring_buffer = (struct hv_ring_buffer *)buffer;
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ring_info->ring_buffer->read_index =
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ring_info->ring_buffer->write_index = 0;
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/* Set the feature bit for enabling flow control. */
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ring_info->ring_buffer->feature_bits.value = 1;
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ring_info->ring_size = buflen;
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ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer);
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spin_lock_init(&ring_info->ring_lock);
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return 0;
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}
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/* Cleanup the ring buffer. */
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void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
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{
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}
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/* Write to the ring buffer. */
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int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
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struct kvec *kv_list, u32 kv_count, bool *signal, bool lock)
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{
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int i = 0;
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u32 bytes_avail_towrite;
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u32 totalbytes_towrite = 0;
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u32 next_write_location;
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u32 old_write;
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u64 prev_indices = 0;
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unsigned long flags = 0;
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for (i = 0; i < kv_count; i++)
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totalbytes_towrite += kv_list[i].iov_len;
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totalbytes_towrite += sizeof(u64);
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if (lock)
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spin_lock_irqsave(&outring_info->ring_lock, flags);
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bytes_avail_towrite = hv_get_bytes_to_write(outring_info);
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/*
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* If there is only room for the packet, assume it is full.
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* Otherwise, the next time around, we think the ring buffer
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* is empty since the read index == write index.
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*/
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if (bytes_avail_towrite <= totalbytes_towrite) {
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if (lock)
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spin_unlock_irqrestore(&outring_info->ring_lock, flags);
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return -EAGAIN;
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}
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/* Write to the ring buffer */
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next_write_location = hv_get_next_write_location(outring_info);
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old_write = next_write_location;
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for (i = 0; i < kv_count; i++) {
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next_write_location = hv_copyto_ringbuffer(outring_info,
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next_write_location,
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kv_list[i].iov_base,
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kv_list[i].iov_len);
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}
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/* Set previous packet start */
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prev_indices = hv_get_ring_bufferindices(outring_info);
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next_write_location = hv_copyto_ringbuffer(outring_info,
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next_write_location,
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&prev_indices,
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sizeof(u64));
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/* Issue a full memory barrier before updating the write index */
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virt_mb();
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/* Now, update the write location */
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hv_set_next_write_location(outring_info, next_write_location);
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if (lock)
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spin_unlock_irqrestore(&outring_info->ring_lock, flags);
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*signal = hv_need_to_signal(old_write, outring_info);
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return 0;
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}
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int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
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void *buffer, u32 buflen, u32 *buffer_actual_len,
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u64 *requestid, bool *signal, bool raw)
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{
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u32 bytes_avail_toread;
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u32 next_read_location = 0;
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u64 prev_indices = 0;
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struct vmpacket_descriptor desc;
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u32 offset;
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u32 packetlen;
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int ret = 0;
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if (buflen <= 0)
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return -EINVAL;
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*buffer_actual_len = 0;
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*requestid = 0;
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bytes_avail_toread = hv_get_bytes_to_read(inring_info);
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/* Make sure there is something to read */
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if (bytes_avail_toread < sizeof(desc)) {
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/*
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* No error is set when there is even no header, drivers are
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* supposed to analyze buffer_actual_len.
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*/
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return ret;
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}
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next_read_location = hv_get_next_read_location(inring_info);
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next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc,
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sizeof(desc),
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next_read_location);
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offset = raw ? 0 : (desc.offset8 << 3);
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packetlen = (desc.len8 << 3) - offset;
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*buffer_actual_len = packetlen;
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*requestid = desc.trans_id;
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if (bytes_avail_toread < packetlen + offset)
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return -EAGAIN;
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if (packetlen > buflen)
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return -ENOBUFS;
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next_read_location =
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hv_get_next_readlocation_withoffset(inring_info, offset);
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next_read_location = hv_copyfrom_ringbuffer(inring_info,
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buffer,
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packetlen,
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next_read_location);
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next_read_location = hv_copyfrom_ringbuffer(inring_info,
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&prev_indices,
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sizeof(u64),
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next_read_location);
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/*
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* Make sure all reads are done before we update the read index since
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* the writer may start writing to the read area once the read index
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* is updated.
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*/
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virt_mb();
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/* Update the read index */
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hv_set_next_read_location(inring_info, next_read_location);
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*signal = hv_need_to_signal_on_read(inring_info);
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return ret;
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}
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