Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 572 insertions, 0 deletions

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
new file mode 100644
index 000000000..7ed6fad3f
--- /dev/null
+++ b/drivers/hv/ring_buffer.c
@@ -0,0 +1,572 @@
+// 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 "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;
+}
+
+/* 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;
+}
+
+/*
+ *
+ * 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)
+{
+	int i;
+	struct page **pages_wraparound;
+
+	BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
+
+	/*
+	 * First page holds struct hv_ring_buffer, do wraparound mapping for
+	 * the rest.
+	 */
+	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;
+
+	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);
+}
+
+/*
+ * Check if the ring buffer spinlock is available to take or not; used on
+ * atomic contexts, like panic path (see the Hyper-V framebuffer driver).
+ */
+
+bool hv_ringbuffer_spinlock_busy(struct vmbus_channel *channel)
+{
+	struct hv_ring_buffer_info *rinfo = &channel->outbound;
+
+	return spin_is_locked(&rinfo->ring_lock);
+}
+EXPORT_SYMBOL_GPL(hv_ringbuffer_spinlock_busy);
+
+/* 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) {
+		++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);
+	}
+
+	/* 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;
+
+	/*
+	 * 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;
+
+	hv_debug_delay_test(channel, MESSAGE_DELAY);
+	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
+		return NULL;
+
+	desc = hv_get_ring_buffer(rbi) + rbi->priv_read_index;
+	if (desc)
+		prefetch((char *)desc + (desc->len8 << 3));
+
+	return desc;
+}
+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);