/* * * 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 <linux/vmalloc.h>#include <linux/slab.h> #include "hyperv_vmbus.h" /* * 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. * * KYS: Oct. 30, 2016: * It looks like Windows hosts have logic to deal with DOS attacks that * can be triggered if it receives interrupts when it is not expecting * the interrupt. The host expects interrupts only when the ring * transitions from empty to non-empty (or full to non full on the guest * to host ring). * So, base the signaling decision solely on the ring state until the * host logic is fixed. */ static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel){	struct hv_ring_buffer_info *rbi = &channel->outbound; 	virt_mb();	if (READ_ONCE(rbi->ring_buffer->interrupt_mask))		return; 	/* 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))		vmbus_setevent(channel); 	return;} /* Get the next write location for the specified ring buffer. */static inline u32hv_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 voidhv_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 u32hv_get_next_read_location(const struct hv_ring_buffer_info *ring_info){	return ring_info->ring_buffer->read_index;} /* * Get the next read location + offset for the specified ring buffer. * This allows the caller to skip. */static inline u32hv_get_next_readlocation_withoffset(const struct hv_ring_buffer_info *ring_info,				    u32 offset){	u32 next = ring_info->ring_buffer->read_index; 	next += offset;	if (next >= ring_info->ring_datasize)		next -= ring_info->ring_datasize; 	return next;} /* Set the next read location for the specified ring buffer. */static inline voidhv_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 u32hv_get_ring_buffersize(const 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 u64hv_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(	const 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); 	memcpy(dest, ring_buffer + start_read_offset, destlen); 	start_read_offset += destlen;	if (start_read_offset >= ring_buffer_size)		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,	const void			*src,	u32				srclen){	void *ring_buffer = hv_get_ring_buffer(ring_info);	u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); 	memcpy(ring_buffer + start_write_offset, src, srclen); 	start_write_offset += srclen;	if (start_write_offset >= ring_buffer_size)		start_write_offset -= ring_buffer_size; 	return start_write_offset;} /* Get various debug metrics for the specified ring buffer. */void hv_ringbuffer_get_debuginfo(const 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,		       struct page *pages, u32 page_cnt){	int i;	struct page **pages_wraparound; 	BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE)); 	memset(ring_info, 0, sizeof(struct hv_ring_buffer_info)); 	/*	 * First page holds struct hv_ring_buffer, do wraparound mapping for	 * the rest.	 */	pages_wraparound = kzalloc(sizeof(struct page *) * (page_cnt * 2 - 1),				   GFP_KERNEL);	if (!pages_wraparound)		return -ENOMEM; 	pages_wraparound[0] = pages;	for (i = 0; i < 2 * (page_cnt - 1); i++)		pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1]; 	ring_info->ring_buffer = (struct hv_ring_buffer *)		vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL); 	kfree(pages_wraparound);  	if (!ring_info->ring_buffer)		return -ENOMEM; 	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 = page_cnt << PAGE_SHIFT;	ring_info->ring_datasize = ring_info->ring_size -		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){	vunmap(ring_info->ring_buffer);} /* Write to the ring buffer. */int hv_ringbuffer_write(struct vmbus_channel *channel,			const struct kvec *kv_list, u32 kv_count){	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;	struct hv_ring_buffer_info *outring_info = &channel->outbound; 	if (channel->rescind)		return -ENODEV; 	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); 	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) {		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);  	spin_unlock_irqrestore(&outring_info->ring_lock, flags); 	hv_signal_on_write(old_write, channel); 	if (channel->rescind)		return -ENODEV; 	return 0;} int hv_ringbuffer_read(struct vmbus_channel *channel,		       void *buffer, u32 buflen, u32 *buffer_actual_len,		       u64 *requestid, 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;	struct hv_ring_buffer_info *inring_info = &channel->inbound; 	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;	} 	init_cached_read_index(channel);	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); 	hv_signal_on_read(channel); 	return ret;}