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Date:   Thu, 1 Aug 2019 16:00:30 -0400
From:   Branden Bonaby <brandonbonaby94@gmail.com>
To:     kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com,
        sashal@kernel.org
Cc:     Branden Bonaby <brandonbonaby94@gmail.com>,
        linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/3] drivers: hv: vmbus: Introduce latency testing
Message-ID: <18193677a879c402d00955c445ae7ce461b4198f.1564527684.git.brandonbonaby94@gmail.com>
References: <cover.1564527684.git.brandonbonaby94@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Introduce user specified latency in the packet reception path.

Signed-off-by: Branden Bonaby <brandonbonaby94@gmail.com>
---
 drivers/hv/connection.c  |  5 +++++
 drivers/hv/ring_buffer.c | 10 ++++++++++
 include/linux/hyperv.h   | 14 ++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 09829e15d4a0..2a2c22f5570e 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -354,9 +354,14 @@ void vmbus_on_event(unsigned long data)
 {
 	struct vmbus_channel *channel = (void *) data;
 	unsigned long time_limit = jiffies + 2;
+	struct vmbus_channel *test_channel = !channel->primary_channel ?
+						channel :
+						channel->primary_channel;
 
 	trace_vmbus_on_event(channel);
 
+	if (unlikely(test_channel->fuzz_testing_buffer_delay > 0))
+		udelay(test_channel->fuzz_testing_buffer_delay);
 	do {
 		void (*callback_fn)(void *);
 
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 9a03b163cbbd..d7627c9023d6 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -395,7 +395,12 @@ struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
 {
 	struct hv_ring_buffer_info *rbi = &channel->inbound;
 	struct vmpacket_descriptor *desc;
+	struct vmbus_channel *test_channel = !channel->primary_channel ?
+						channel :
+						channel->primary_channel;
 
+	if (unlikely(test_channel->fuzz_testing_message_delay > 0))
+		udelay(test_channel->fuzz_testing_message_delay);
 	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
 		return NULL;
 
@@ -420,7 +425,12 @@ __hv_pkt_iter_next(struct vmbus_channel *channel,
 	struct hv_ring_buffer_info *rbi = &channel->inbound;
 	u32 packetlen = desc->len8 << 3;
 	u32 dsize = rbi->ring_datasize;
+	struct vmbus_channel *test_channel = !channel->primary_channel ?
+						channel :
+						channel->primary_channel;
 
+	if (unlikely(test_channel->fuzz_testing_message_delay > 0))
+		udelay(test_channel->fuzz_testing_message_delay);
 	/* bump offset to next potential packet */
 	rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
 	if (rbi->priv_read_index >= dsize)
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 6256cc34c4a6..8d068956dd67 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -23,6 +23,7 @@
 #include <linux/mod_devicetable.h>
 #include <linux/interrupt.h>
 #include <linux/reciprocal_div.h>
+#include <linux/delay.h>
 
 #define MAX_PAGE_BUFFER_COUNT				32
 #define MAX_MULTIPAGE_BUFFER_COUNT			32 /* 128K */
@@ -926,6 +927,19 @@ struct vmbus_channel {
 	 * full outbound ring buffer.
 	 */
 	u64 out_full_first;
+
+	/* enabling/disabling fuzz testing on the channel (default is false)*/
+	bool fuzz_testing_state;
+
+	/* Buffer delay will delay the guest from emptying the ring buffer
+	 * for a specific amount of time. The delay is in microseconds and will
+	 * be between 1 to a maximum of 1000, its default is 0 (no delay).
+	 * The  Message delay will delay guest reading on a per message basis
+	 * in microseconds between 1 to 1000 with the default being 0
+	 * (no delay).
+	 */
+	u32 fuzz_testing_buffer_delay;
+	u32 fuzz_testing_message_delay;
 };
 
 static inline bool is_hvsock_channel(const struct vmbus_channel *c)
-- 
2.17.1