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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *
  * Copyright (c) 2009, Microsoft Corporation.
  *
  * 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 <linux/prefetch.h>
 #include <linux/io.h>
 #include <asm/mshyperv.h>
 
 #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)) {
         ++channel->intr_out_empty;
         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;
 }
 
 /* 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;
 }
 
 /*
  *
  * hv_get_ringbuffer_availbytes()
  *
  * Get number of bytes available to read and to write to
  * for the specified ring buffer
  */
 static void
 hv_get_ringbuffer_availbytes(const struct hv_ring_buffer_info *rbi,
                  u32 *read, u32 *write)
 {
     u32 read_loc, write_loc, dsize;
 
     /* Capture the read/write indices before they changed */
     read_loc = READ_ONCE(rbi->ring_buffer->read_index);
     write_loc = READ_ONCE(rbi->ring_buffer->write_index);
     dsize = rbi->ring_datasize;
 
     *write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
         read_loc - write_loc;
     *read = dsize - *write;
 }
 
 /* Get various debug metrics for the specified ring buffer. */
 int 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;
 
     mutex_lock(&ring_info->ring_buffer_mutex);
 
     if (!ring_info->ring_buffer) {
         mutex_unlock(&ring_info->ring_buffer_mutex);
         return -EINVAL;
     }
 
     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;
     mutex_unlock(&ring_info->ring_buffer_mutex);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(hv_ringbuffer_get_debuginfo);
 
 /* Initialize a channel's ring buffer info mutex locks */
 void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
 {
     mutex_init(&channel->inbound.ring_buffer_mutex);
     mutex_init(&channel->outbound.ring_buffer_mutex);
 }
 
 /* Initialize the ring buffer. */
 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
                struct page *pages, u32 page_cnt, u32 max_pkt_size)
 {
     struct page **pages_wraparound;
     unsigned long *pfns_wraparound;
     u64 pfn;
     int i;
 
     BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
 
     /*
      * First page holds struct hv_ring_buffer, do wraparound mapping for
      * the rest.
      */
     if (hv_isolation_type_snp()) {
         pfn = page_to_pfn(pages) +
             PFN_DOWN(ms_hyperv.shared_gpa_boundary);
 
         pfns_wraparound = kcalloc(page_cnt * 2 - 1,
             sizeof(unsigned long), GFP_KERNEL);
         if (!pfns_wraparound)
             return -ENOMEM;
 
         pfns_wraparound[0] = pfn;
         for (i = 0; i < 2 * (page_cnt - 1); i++)
             pfns_wraparound[i + 1] = pfn + i % (page_cnt - 1) + 1;
 
         ring_info->ring_buffer = (struct hv_ring_buffer *)
             vmap_pfn(pfns_wraparound, page_cnt * 2 - 1,
                  PAGE_KERNEL);
         kfree(pfns_wraparound);
 
         if (!ring_info->ring_buffer)
             return -ENOMEM;
 
         /* Zero ring buffer after setting memory host visibility. */
         memset(ring_info->ring_buffer, 0x00, PAGE_SIZE * page_cnt);
     } else {
         pages_wraparound = kcalloc(page_cnt * 2 - 1,
                        sizeof(struct page *),
                        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_size_div10_reciprocal =
         reciprocal_value(ring_info->ring_size / 10);
     ring_info->ring_datasize = ring_info->ring_size -
         sizeof(struct hv_ring_buffer);
     ring_info->priv_read_index = 0;
 
     /* Initialize buffer that holds copies of incoming packets */
     if (max_pkt_size) {
         ring_info->pkt_buffer = kzalloc(max_pkt_size, GFP_KERNEL);
         if (!ring_info->pkt_buffer)
             return -ENOMEM;
         ring_info->pkt_buffer_size = max_pkt_size;
     }
 
     spin_lock_init(&ring_info->ring_lock);
 
     return 0;
 }
 
 /* Cleanup the ring buffer. */
 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
 {
     mutex_lock(&ring_info->ring_buffer_mutex);
     vunmap(ring_info->ring_buffer);
     ring_info->ring_buffer = NULL;
     mutex_unlock(&ring_info->ring_buffer_mutex);
 
     kfree(ring_info->pkt_buffer);
     ring_info->pkt_buffer = NULL;
     ring_info->pkt_buffer_size = 0;
 }
 
 /* Write to the ring buffer. */
 int hv_ringbuffer_write(struct vmbus_channel *channel,
             const struct kvec *kv_list, u32 kv_count,
             u64 requestid, u64 *trans_id)
 {
     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;
     struct vmpacket_descriptor *desc = kv_list[0].iov_base;
     u64 __trans_id, rqst_id = VMBUS_NO_RQSTOR;
 
     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) {
         ++channel->out_full_total;
 
         if (!channel->out_full_flag) {
             ++channel->out_full_first;
             channel->out_full_flag = true;
         }
 
         spin_unlock_irqrestore(&outring_info->ring_lock, flags);
         return -EAGAIN;
     }
 
     channel->out_full_flag = false;
 
     /* 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);
     }
 
     /*
      * Allocate the request ID after the data has been copied into the
      * ring buffer.  Once this request ID is allocated, the completion
      * path could find the data and free it.
      */
 
     if (desc->flags == VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED) {
         if (channel->next_request_id_callback != NULL) {
             rqst_id = channel->next_request_id_callback(channel, requestid);
             if (rqst_id == VMBUS_RQST_ERROR) {
                 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
                 return -EAGAIN;
             }
         }
     }
     desc = hv_get_ring_buffer(outring_info) + old_write;
     __trans_id = (rqst_id == VMBUS_NO_RQSTOR) ? requestid : rqst_id;
     /*
      * Ensure the compiler doesn't generate code that reads the value of
      * the transaction ID from the ring buffer, which is shared with the
      * Hyper-V host and subject to being changed at any time.
      */
     WRITE_ONCE(desc->trans_id, __trans_id);
     if (trans_id)
         *trans_id = __trans_id;
 
     /* 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) {
         if (rqst_id != VMBUS_NO_RQSTOR) {
             /* Reclaim request ID to avoid leak of IDs */
             if (channel->request_addr_callback != NULL)
                 channel->request_addr_callback(channel, rqst_id);
         }
         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;
 
     /*
      * The Hyper-V host writes the packet data, then uses
      * store_release() to update the write_index.  Use load_acquire()
      * here to prevent loads of the packet data from being re-ordered
      * before the read of the write_index and potentially getting
      * stale data.
      */
     write_loc = virt_load_acquire(&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;
     struct vmpacket_descriptor *desc, *desc_copy;
     u32 bytes_avail, pkt_len, pkt_offset;
 
     hv_debug_delay_test(channel, MESSAGE_DELAY);
 
     bytes_avail = hv_pkt_iter_avail(rbi);
     if (bytes_avail < sizeof(struct vmpacket_descriptor))
         return NULL;
     bytes_avail = min(rbi->pkt_buffer_size, bytes_avail);
 
     desc = (struct vmpacket_descriptor *)(hv_get_ring_buffer(rbi) + rbi->priv_read_index);
 
     /*
      * Ensure the compiler does not use references to incoming Hyper-V values (which
      * could change at any moment) when reading local variables later in the code
      */
     pkt_len = READ_ONCE(desc->len8) << 3;
     pkt_offset = READ_ONCE(desc->offset8) << 3;
 
     /*
      * If pkt_len is invalid, set it to the smaller of hv_pkt_iter_avail() and
      * rbi->pkt_buffer_size
      */
     if (pkt_len < sizeof(struct vmpacket_descriptor) || pkt_len > bytes_avail)
         pkt_len = bytes_avail;
 
     /*
      * If pkt_offset is invalid, arbitrarily set it to
      * the size of vmpacket_descriptor
      */
     if (pkt_offset < sizeof(struct vmpacket_descriptor) || pkt_offset > pkt_len)
         pkt_offset = sizeof(struct vmpacket_descriptor);
 
     /* Copy the Hyper-V packet out of the ring buffer */
     desc_copy = (struct vmpacket_descriptor *)rbi->pkt_buffer;
     memcpy(desc_copy, desc, pkt_len);
 
     /*
      * Hyper-V could still change len8 and offset8 after the earlier read.
      * Ensure that desc_copy has legal values for len8 and offset8 that
      * are consistent with the copy we just made
      */
     desc_copy->len8 = pkt_len >> 3;
     desc_copy->offset8 = pkt_offset >> 3;
 
     return desc_copy;
 }
 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;
 
     hv_debug_delay_test(channel, MESSAGE_DELAY);
     /* 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);
 
 /* How many bytes were read in this iterator cycle */
 static u32 hv_pkt_iter_bytes_read(const struct hv_ring_buffer_info *rbi,
                     u32 start_read_index)
 {
     if (rbi->priv_read_index >= start_read_index)
         return rbi->priv_read_index - start_read_index;
     else
         return rbi->ring_datasize - start_read_index +
             rbi->priv_read_index;
 }
 
 /*
  * Update host ring buffer after iterating over packets. If the host has
  * stopped queuing new entries because it found the ring buffer full, and
  * sufficient space is being freed up, signal the host. But be careful to
  * only signal the host when necessary, both for performance reasons and
  * because Hyper-V protects itself by throttling guests that signal
  * inappropriately.
  *
  * Determining when to signal is tricky. There are three key data inputs
  * that must be handled in this order to avoid race conditions:
  *
  * 1. Update the read_index
  * 2. Read the pending_send_sz
  * 3. Read the current write_index
  *
  * The interrupt_mask is not used to determine when to signal. The
  * interrupt_mask is used only on the guest->host ring buffer when
  * sending requests to the host. The host does not use it on the host->
  * guest ring buffer to indicate whether it should be signaled.
  */
 void hv_pkt_iter_close(struct vmbus_channel *channel)
 {
     struct hv_ring_buffer_info *rbi = &channel->inbound;
     u32 curr_write_sz, pending_sz, bytes_read, start_read_index;
 
     /*
      * 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();
     start_read_index = rbi->ring_buffer->read_index;
     rbi->ring_buffer->read_index = rbi->priv_read_index;
 
     /*
      * Older versions of Hyper-V (before WS2102 and Win8) do not
      * implement pending_send_sz and simply poll if the host->guest
      * ring buffer is full.  No signaling is needed or expected.
      */
     if (!rbi->ring_buffer->feature_bits.feat_pending_send_sz)
         return;
 
     /*
      * Issue a full memory barrier before making the signaling decision.
      * If reading pending_send_sz were to be reordered and happen
      * before we commit the new read_index, a race could occur.  If the
      * host were to set the pending_send_sz after we have sampled
      * pending_send_sz, and the ring buffer blocks before we commit the
      * read index, we could miss sending the interrupt. Issue a full
      * memory barrier to address this.
      */
     virt_mb();
 
     /*
      * If the pending_send_sz is zero, then the ring buffer is not
      * blocked and there is no need to signal.  This is far by the
      * most common case, so exit quickly for best performance.
      */
     pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
     if (!pending_sz)
         return;
 
     /*
      * Ensure the read of write_index in hv_get_bytes_to_write()
      * happens after the read of pending_send_sz.
      */
     virt_rmb();
     curr_write_sz = hv_get_bytes_to_write(rbi);
     bytes_read = hv_pkt_iter_bytes_read(rbi, start_read_index);
 
     /*
      * We want to signal the host only if we're transitioning
      * from a "not enough free space" state to a "enough free
      * space" state.  For example, it's possible that this function
      * could run and free up enough space to signal the host, and then
      * run again and free up additional space before the host has a
      * chance to clear the pending_send_sz.  The 2nd invocation would
      * be a null transition from "enough free space" to "enough free
      * space", which doesn't warrant a signal.
      *
      * Exactly filling the ring buffer is treated as "not enough
      * space". The ring buffer always must have at least one byte
      * empty so the empty and full conditions are distinguishable.
      * hv_get_bytes_to_write() doesn't fully tell the truth in
      * this regard.
      *
      * So first check if we were in the "enough free space" state
      * before we began the iteration. If so, the host was not
      * blocked, and there's no need to signal.
      */
     if (curr_write_sz - bytes_read > pending_sz)
         return;
 
     /*
      * Similarly, if the new state is "not enough space", then
      * there's no need to signal.
      */
     if (curr_write_sz <= pending_sz)
         return;
 
     ++channel->intr_in_full;
     vmbus_setevent(channel);
 }
 EXPORT_SYMBOL_GPL(hv_pkt_iter_close);

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