/* * * 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 * Hank Janssen * K. Y. Srinivasan * */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include "hyperv_vmbus.h" #define VMBUS_PKT_TRAILER 8 /* * 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); } /* 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; } /* 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(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 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 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; } } EXPORT_SYMBOL_GPL(hv_ringbuffer_get_debuginfo); /* 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; u32 bytes_avail_towrite; u32 totalbytes_towrite = sizeof(u64); u32 next_write_location; u32 old_write; u64 prev_indices; unsigned long flags; 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; 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) { struct vmpacket_descriptor *desc; u32 packetlen, offset; if (unlikely(buflen == 0)) return -EINVAL; *buffer_actual_len = 0; *requestid = 0; /* Make sure there is something to read */ desc = hv_pkt_iter_first(channel); if (desc == NULL) { /* * No error is set when there is even no header, drivers are * supposed to analyze buffer_actual_len. */ return 0; } offset = raw ? 0 : (desc->offset8 << 3); packetlen = (desc->len8 << 3) - offset; *buffer_actual_len = packetlen; *requestid = desc->trans_id; if (unlikely(packetlen > buflen)) return -ENOBUFS; /* since ring is double mapped, only one copy is necessary */ memcpy(buffer, (const char *)desc + offset, packetlen); /* Advance ring index to next packet descriptor */ __hv_pkt_iter_next(channel, desc); /* Notify host of update */ hv_pkt_iter_close(channel); return 0; } /* * Determine number of bytes available in ring buffer after * the current iterator (priv_read_index) location. * * This is similar to hv_get_bytes_to_read but with private * read index instead. */ static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi) { u32 priv_read_loc = rbi->priv_read_index; u32 write_loc = READ_ONCE(rbi->ring_buffer->write_index); if (write_loc >= priv_read_loc) return write_loc - priv_read_loc; else return (rbi->ring_datasize - priv_read_loc) + write_loc; } /* * Get first vmbus packet from ring buffer after read_index * * If ring buffer is empty, returns NULL and no other action needed. */ struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel) { struct hv_ring_buffer_info *rbi = &channel->inbound; if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor)) return NULL; return hv_get_ring_buffer(rbi) + rbi->priv_read_index; } EXPORT_SYMBOL_GPL(hv_pkt_iter_first); /* * Get next vmbus packet from ring buffer. * * Advances the current location (priv_read_index) and checks for more * data. If the end of the ring buffer is reached, then return NULL. */ struct vmpacket_descriptor * __hv_pkt_iter_next(struct vmbus_channel *channel, const struct vmpacket_descriptor *desc) { struct hv_ring_buffer_info *rbi = &channel->inbound; u32 packetlen = desc->len8 << 3; u32 dsize = rbi->ring_datasize; /* bump offset to next potential packet */ rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER; if (rbi->priv_read_index >= dsize) rbi->priv_read_index -= dsize; /* more data? */ return hv_pkt_iter_first(channel); } EXPORT_SYMBOL_GPL(__hv_pkt_iter_next); /* * Update host ring buffer after iterating over packets. */ void hv_pkt_iter_close(struct vmbus_channel *channel) { struct hv_ring_buffer_info *rbi = &channel->inbound; u32 orig_write_sz = hv_get_bytes_to_write(rbi); /* * 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_rmb(); rbi->ring_buffer->read_index = rbi->priv_read_index; /* * Issue a full memory barrier before making the signaling decision. * Here is the reason for having this barrier: * If the reading of the pend_sz (in this function) * were to be reordered and read before we commit the new read * index (in the calling function) we could * have a problem. If the host were to set the pending_sz after we * have sampled pending_sz and go to sleep before we commit the * read index, we could miss sending the interrupt. Issue a full * memory barrier to address this. */ virt_mb(); /* If host has disabled notifications then skip */ if (rbi->ring_buffer->interrupt_mask) return; if (rbi->ring_buffer->feature_bits.feat_pending_send_sz) { u32 pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz); /* * If there was space before we began iteration, * then host was not blocked. Also handles case where * pending_sz is zero then host has nothing pending * and does not need to be signaled. */ if (orig_write_sz > pending_sz) return; /* If pending write will not fit, don't give false hope. */ if (hv_get_bytes_to_write(rbi) < pending_sz) return; } vmbus_setevent(channel); } EXPORT_SYMBOL_GPL(hv_pkt_iter_close);