Revert "Drivers: hv: vmbus: Copy packets sent by Hyper-V out of the ring buffer"

This reverts commit a8c3209998afb5c4941b49e35b513cea9050cb4a.

It is reported that the said commit caused regression in netvsc.

Reported-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

5 files changed, 15 insertions, 80 deletions

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 9aa789e5f22b..0bd202de7960 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -597,15 +597,12 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
 	newchannel->onchannel_callback = onchannelcallback;
 	newchannel->channel_callback_context = context;
 
-	if (!newchannel->max_pkt_size)
-		newchannel->max_pkt_size = VMBUS_DEFAULT_MAX_PKT_SIZE;
-
-	err = hv_ringbuffer_init(&newchannel->outbound, page, send_pages, 0);
+	err = hv_ringbuffer_init(&newchannel->outbound, page, send_pages);
 	if (err)
 		goto error_clean_ring;
 
-	err = hv_ringbuffer_init(&newchannel->inbound, &page[send_pages],
-				 recv_pages, newchannel->max_pkt_size);
+	err = hv_ringbuffer_init(&newchannel->inbound,
+				 &page[send_pages], recv_pages);
 	if (err)
 		goto error_clean_ring;
 
diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
index 660036da7449..59ce85e00a02 100644
--- a/drivers/hv/hv_fcopy.c
+++ b/drivers/hv/hv_fcopy.c
@@ -349,7 +349,6 @@ int hv_fcopy_init(struct hv_util_service *srv)
 {
 	recv_buffer = srv->recv_buffer;
 	fcopy_transaction.recv_channel = srv->channel;
-	fcopy_transaction.recv_channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2;
 
 	/*
 	 * When this driver loads, the user level daemon that
diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index c698592b83e4..b49962d312ce 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -757,7 +757,6 @@ hv_kvp_init(struct hv_util_service *srv)
 {
 	recv_buffer = srv->recv_buffer;
 	kvp_transaction.recv_channel = srv->channel;
-	kvp_transaction.recv_channel->max_pkt_size = HV_HYP_PAGE_SIZE * 4;
 
 	/*
 	 * When this driver loads, the user level daemon that
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 42f3d9d123a1..9416e09ebd58 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -174,7 +174,7 @@ extern int hv_synic_cleanup(unsigned int cpu);
 void hv_ringbuffer_pre_init(struct vmbus_channel *channel);
 
 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
-		       struct page *pages, u32 pagecnt, u32 max_pkt_size);
+		       struct page *pages, u32 pagecnt);
 
 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info);
 
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 29e90477363a..35833d4d1a1d 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -190,7 +190,7 @@ void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
 
 /* 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, u32 page_cnt)
 {
 	int i;
 	struct page **pages_wraparound;
@@ -232,14 +232,6 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 		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;
@@ -252,9 +244,6 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
 	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_size = 0;
 }
 
 /* Write to the ring buffer. */
@@ -396,7 +385,7 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
 	memcpy(buffer, (const char *)desc + offset, packetlen);
 
 	/* Advance ring index to next packet descriptor */
-	__hv_pkt_iter_next(channel, desc, true);
+	__hv_pkt_iter_next(channel, desc);
 
 	/* Notify host of update */
 	hv_pkt_iter_close(channel);
@@ -423,22 +412,6 @@ static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
 }
 
 /*
- * Get first vmbus packet without copying it out of the ring buffer
- */
-struct vmpacket_descriptor *hv_pkt_iter_first_raw(struct vmbus_channel *channel)
-{
-	struct hv_ring_buffer_info *rbi = &channel->inbound;
-
-	hv_debug_delay_test(channel, MESSAGE_DELAY);
-
-	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
-		return NULL;
-
-	return (struct vmpacket_descriptor *)(hv_get_ring_buffer(rbi) + rbi->priv_read_index);
-}
-EXPORT_SYMBOL_GPL(hv_pkt_iter_first_raw);
-
-/*
  * Get first vmbus packet from ring buffer after read_index
  *
  * If ring buffer is empty, returns NULL and no other action needed.
@@ -446,49 +419,17 @@ EXPORT_SYMBOL_GPL(hv_pkt_iter_first_raw);
 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;
+	struct vmpacket_descriptor *desc;
 
-	desc = hv_pkt_iter_first_raw(channel);
-	if (!desc)
+	hv_debug_delay_test(channel, MESSAGE_DELAY);
+	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
 		return NULL;
 
-	bytes_avail = min(rbi->pkt_buffer_size, hv_pkt_iter_avail(rbi));
-
-	/*
-	 * 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;
+	desc = hv_get_ring_buffer(rbi) + rbi->priv_read_index;
+	if (desc)
+		prefetch((char *)desc + (desc->len8 << 3));
 
-	return desc_copy;
+	return desc;
 }
 EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
 
@@ -500,8 +441,7 @@ EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
  */
 struct vmpacket_descriptor *
 __hv_pkt_iter_next(struct vmbus_channel *channel,
-		   const struct vmpacket_descriptor *desc,
-		   bool copy)
+		   const struct vmpacket_descriptor *desc)
 {
 	struct hv_ring_buffer_info *rbi = &channel->inbound;
 	u32 packetlen = desc->len8 << 3;
@@ -514,7 +454,7 @@ __hv_pkt_iter_next(struct vmbus_channel *channel,
 		rbi->priv_read_index -= dsize;
 
 	/* more data? */
-	return copy ? hv_pkt_iter_first(channel) : hv_pkt_iter_first_raw(channel);
+	return hv_pkt_iter_first(channel);
 }
 EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);