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Groups > linux.kernel > #1513427

[PATCH V2 01/14] Drivers: hv: ring_buffer: count on wrap around mappings in get_next_pkt_raw() (v2)

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From: Vitaly Kuznetsov <vkuznets@redhat.com>

With wrap around mappings in place we can always provide drivers with
direct links to packets on the ring buffer, even when they wrap around.
Do the required updates to get_next_pkt_raw()/put_pkt_raw()

The first version of this commit was reverted (65a532f3d50a) to deal with
cross-tree merge issues which are (hopefully) resolved now.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Tested-by: Dexuan Cui <decui@microsoft.com>
---
 include/linux/hyperv.h |   32 +++++++++++---------------------
 1 files changed, 11 insertions(+), 21 deletions(-)

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 6824556..42ae6a5 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1526,31 +1526,23 @@ static inline  bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
 get_next_pkt_raw(struct vmbus_channel *channel)
 {
 	struct hv_ring_buffer_info *ring_info = &channel->inbound;
-	u32 read_loc = ring_info->priv_read_index;
+	u32 priv_read_loc = ring_info->priv_read_index;
 	void *ring_buffer = hv_get_ring_buffer(ring_info);
-	struct vmpacket_descriptor *cur_desc;
-	u32 packetlen;
 	u32 dsize = ring_info->ring_datasize;
-	u32 delta = read_loc - ring_info->ring_buffer->read_index;
+	/*
+	 * delta is the difference between what is available to read and
+	 * what was already consumed in place. We commit read index after
+	 * the whole batch is processed.
+	 */
+	u32 delta = priv_read_loc >= ring_info->ring_buffer->read_index ?
+		priv_read_loc - ring_info->ring_buffer->read_index :
+		(dsize - ring_info->ring_buffer->read_index) + priv_read_loc;
 	u32 bytes_avail_toread = (hv_get_bytes_to_read(ring_info) - delta);
 
 	if (bytes_avail_toread < sizeof(struct vmpacket_descriptor))
 		return NULL;
 
-	if ((read_loc + sizeof(*cur_desc)) > dsize)
-		return NULL;
-
-	cur_desc = ring_buffer + read_loc;
-	packetlen = cur_desc->len8 << 3;
-
-	/*
-	 * If the packet under consideration is wrapping around,
-	 * return failure.
-	 */
-	if ((read_loc + packetlen + VMBUS_PKT_TRAILER) > (dsize - 1))
-		return NULL;
-
-	return cur_desc;
+	return ring_buffer + priv_read_loc;
 }
 
 /*
@@ -1562,16 +1554,14 @@ static inline void put_pkt_raw(struct vmbus_channel *channel,
 				struct vmpacket_descriptor *desc)
 {
 	struct hv_ring_buffer_info *ring_info = &channel->inbound;
-	u32 read_loc = ring_info->priv_read_index;
 	u32 packetlen = desc->len8 << 3;
 	u32 dsize = ring_info->ring_datasize;
 
-	if ((read_loc + packetlen + VMBUS_PKT_TRAILER) > dsize)
-		BUG();
 	/*
 	 * Include the packet trailer.
 	 */
 	ring_info->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
+	ring_info->priv_read_index %= dsize;
 }
 
 /*
-- 
1.7.4.1

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[PATCH V2 00/14] Drivers: hv: Some miscellaneous fixes and enhancements  kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
  [PATCH V2 08/14] Drivers: hv: balloon: Fix info request to show max page count kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
    Re: [PATCH V2 08/14] Drivers: hv: balloon: Fix info request to show  max page count Dan Carpenter <dan.carpenter@oracle.com> - 2016-11-10 20:20 +0100
      RE: [PATCH V2 08/14] Drivers: hv: balloon: Fix info request to show  max page count "Alex Ng (LIS)" <alexng@microsoft.com> - 2016-11-11 00:20 +0100
  [PATCH V2 04/14] Drivers: hv: balloon: Disable hot add when CONFIG_MEMORY_HOTPLUG is not set kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
  [PATCH V2 02/14] Drivers: hv: utils: reduce HV_UTIL_NEGO_TIMEOUT timeout kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
  [PATCH V2 12/14] Drivers: hv: vmbus: Base host signaling strictly on the ring state kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
  [PATCH V2 03/14] Drivers: hv: utils: Fix the mapping between host version and protocol to use kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
  [PATCH V2 11/14] tools: hv: remove unnecessary header files and netlink related code kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
  [PATCH V2 14/14] Drivers: hv: vmbus: On the read path cleanup the logic to interrupt the host kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
  [PATCH V2 07/14] Drivers: hv: vss: Operation timeouts should match host expectation kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
  [PATCH V2 01/14] Drivers: hv: ring_buffer: count on wrap around mappings in get_next_pkt_raw() (v2) kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
    [PATCH V2 10/14] tools: hv: fix a compile warning in snprintf kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
    [PATCH V2 06/14] Drivers: hv: vss: Improve log messages. kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
    [PATCH V2 09/14] tools: hv: remove unnecessary link flag kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
    [PATCH V2 13/14] Drivers: hv: vmbus: On write cleanup the logic to interrupt the host kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
    [PATCH V2 05/14] Drivers: hv: balloon: Add logging for dynamic memory operations kys@exchange.microsoft.com - 2016-11-01 19:20 +0100

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