[PATCH 3/4] kvm tools: Add debug feature to test the IO thread

[Sasha Levin <levinsasha928@xxxxxxxxx>]

Add --debug-io-delay-cycles and --debug-io-delay-amount to delay the completion of IO requests within virtio-blk.
This feature allows to verify and debug the threading within virtio-blk.

Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
---
 tools/kvm/include/kvm/virtio-blk.h |    6 +++++-
 tools/kvm/kvm-run.c                |   10 +++++++++-
 tools/kvm/virtio-blk.c             |   11 +++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/tools/kvm/include/kvm/virtio-blk.h b/tools/kvm/include/kvm/virtio-blk.h
index 9e91035..c0211a0 100644
--- a/tools/kvm/include/kvm/virtio-blk.h
+++ b/tools/kvm/include/kvm/virtio-blk.h
@@ -1,10 +1,14 @@
 #ifndef KVM__BLK_VIRTIO_H
 #define KVM__BLK_VIRTIO_H
 
+#include <stdint.h>
+
 struct kvm;
 
 struct virtio_blk_parameters {
-	struct kvm *self;
+	struct kvm	*self;
+	uint64_t	debug_delay_cycles;
+	uint64_t	debug_delay_amount;
 };
 
 void virtio_blk__init(struct virtio_blk_parameters *params);
diff --git a/tools/kvm/kvm-run.c b/tools/kvm/kvm-run.c
index 5b71fb4..3392bfa 100644
--- a/tools/kvm/kvm-run.c
+++ b/tools/kvm/kvm-run.c
@@ -57,6 +57,8 @@ static void handle_sigalrm(int sig)
 }
 
 static u64 ram_size = MIN_RAM_SIZE_MB;
+static u64 virtio_blk_delay_cycles = -1;
+static u64 virtio_blk_delay_amount;
 static const char *kernel_cmdline;
 static const char *kernel_filename;
 static const char *initrd_filename;
@@ -112,6 +114,10 @@ static const struct option options[] = {
 			"Enable single stepping"),
 	OPT_BOOLEAN('g', "ioport-debug", &ioport_debug,
 			"Enable ioport debugging"),
+	OPT_U64('\0', "debug-io-delay-cycles", &virtio_blk_delay_cycles,
+			"Wait this amount of cycles before delay"),
+	OPT_U64('\0', "debug-io-delay-amount", &virtio_blk_delay_amount,
+			"Delay each I/O request by this amount (usec)"),
 	OPT_END()
 };
 
@@ -319,7 +325,9 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
 	pci__init();
 
 	blk_params = (struct virtio_blk_parameters) {
-		.self				= kvm
+		.self				= kvm,
+		.debug_delay_cycles = virtio_blk_delay_cycles,
+		.debug_delay_amount = virtio_blk_delay_amount
 	};
 
 	virtio_blk__init(&blk_params);
diff --git a/tools/kvm/virtio-blk.c b/tools/kvm/virtio-blk.c
index 2470583..ea8c4e7 100644
--- a/tools/kvm/virtio-blk.c
+++ b/tools/kvm/virtio-blk.c
@@ -38,6 +38,9 @@ struct blk_device {
 	uint16_t			queue_selector;
 	uint64_t			virtio_blk_queue_set_flags;
 
+	uint64_t			debug_delay_cycles;
+	uint64_t			debug_delay_amount;
+
 	struct virt_queue		vqs[NUM_VIRT_QUEUES];
 };
 
@@ -174,6 +177,7 @@ static int virtio_blk_get_selected_queue(void)
 static void *virtio_blk_io_thread(void *ptr)
 {
 	struct kvm *self = ptr;
+	uint64_t io_cycles = 0;
 	int ret;
 	mutex_lock(&blk_device.io_mutex);
 	ret = pthread_cond_wait(&blk_device.io_cond, &blk_device.io_mutex);
@@ -183,6 +187,10 @@ static void *virtio_blk_io_thread(void *ptr)
 		while (queue_index >= 0) {
 			struct virt_queue *vq = &blk_device.vqs[queue_index];
 
+			if (blk_device.debug_delay_cycles != (uint64_t)-1 &&
+				++io_cycles > blk_device.debug_delay_cycles)
+					usleep(blk_device.debug_delay_amount);
+
 			while (virt_queue__available(vq))
 				virtio_blk_do_io_request(self, vq);
 
@@ -293,6 +301,9 @@ void virtio_blk__init(struct virtio_blk_parameters *params)
 	if (!self->disk_image)
 		return;
 
+	blk_device.debug_delay_amount = params->debug_delay_amount;
+	blk_device.debug_delay_cycles = params->debug_delay_cycles;
+
 	pthread_create(&blk_device.io_thread, NULL, virtio_blk_io_thread, self);
 
 	blk_device.blk_config.capacity = self->disk_image->size / SECTOR_SIZE;
-- 
1.7.5.rc1

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