[RFC] generic NVMe target and NVMe loop driver

[RFC] generic NVMe target and NVMe loop driver

[Christoph Hellwig]

This series continues the NVMe host drive split and also starts adding a
consume for it.  The consumer is mostly interesting for developers at this
point as it's simply a 'loopback' NVMe device that ties the split NVMe
driver fronted into the new generic NVMe target subsystem.  This was
developed for our NVMe over Fabrics prototype, but will also be useful for
other work like Ming's virtio-nvme or event an implementation traditional
PCIe NVMe using vhost.

The biggest gap at this point is aborts and resets, which are still under
heavy development.  Once those are done and I've finished the configfs
layout the code will hopefully be ready for inclusion in Linux 4.5.

I've also written a python based shell to ease configuration of the target
subsystem which I'll hopefully be able to release soon.

As this depends on a lot of pending NVMe patch a git tree is also
available:

	http://git.infradead.org/users/hch/block.git/shortlog/refs/heads/nvme-loop.2

[PATCH 1/8] nvme: move set_queue_count to common code

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/nvme/host/core.c | 17 +++++++++++++++++
 drivers/nvme/host/nvme.h |  1 +
 drivers/nvme/host/pci.c  | 19 +------------------
 3 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 3600a0c..a63a71a 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -334,6 +334,23 @@ int nvme_get_log_page(struct nvme_ctrl *dev, struct nvme_smart_log **log)
 	return error;
 }
 
+int nvme_set_queue_count(struct nvme_ctrl *ctrl, int count)
+{
+	int status;
+	u32 result;
+	u32 q_count = (count - 1) | ((count - 1) << 16);
+
+	status = nvme_set_features(ctrl, NVME_FEAT_NUM_QUEUES, q_count, 0,
+			&result);
+	if (status < 0)
+		return status;
+	if (status > 0) {
+		dev_err(ctrl->dev, "Could not set queue count (%d)\n", status);
+		return 0;
+	}
+	return min(result & 0xffff, result >> 16) + 1;
+}
+
 static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
 {
 	struct nvme_user_io io;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index d72bbe0..1692fda 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -227,6 +227,7 @@ int nvme_get_features(struct nvme_ctrl *dev, unsigned fid, unsigned nsid,
 			dma_addr_t dma_addr, u32 *result);
 int nvme_set_features(struct nvme_ctrl *dev, unsigned fid, unsigned dword11,
 			dma_addr_t dma_addr, u32 *result);
+int nvme_set_queue_count(struct nvme_ctrl *ctrl, int count);
 
 extern spinlock_t dev_list_lock;
 
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 2ef408f..89d2442 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1464,23 +1464,6 @@ static void nvme_create_io_queues(struct nvme_dev *dev)
 		}
 }
 
-static int set_queue_count(struct nvme_dev *dev, int count)
-{
-	int status;
-	u32 result;
-	u32 q_count = (count - 1) | ((count - 1) << 16);
-
-	status = nvme_set_features(&dev->ctrl, NVME_FEAT_NUM_QUEUES, q_count, 0,
-								&result);
-	if (status < 0)
-		return status;
-	if (status > 0) {
-		dev_err(dev->dev, "Could not set queue count (%d)\n", status);
-		return 0;
-	}
-	return min(result & 0xffff, result >> 16) + 1;
-}
-
 static void __iomem *nvme_map_cmb(struct nvme_dev *dev)
 {
 	u64 szu, size, offset;
@@ -1545,7 +1528,7 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
 	int result, i, vecs, nr_io_queues, size;
 
 	nr_io_queues = num_possible_cpus();
-	result = set_queue_count(dev, nr_io_queues);
+	result = nvme_set_queue_count(&dev->ctrl, nr_io_queues);
 	if (result <= 0)
 		return result;
 	if (result < nr_io_queues)
-- 
1.9.1

[PATCH 2/8] nvme: move enable/disable/shutdown_ctrl to common code

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/nvme/host/core.c | 87 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/nvme/host/nvme.h |  4 +++
 drivers/nvme/host/pci.c  | 94 +++++-------------------------------------------
 3 files changed, 100 insertions(+), 85 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index a63a71a..c061a6a 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -14,6 +14,7 @@
 
 #include <linux/blkdev.h>
 #include <linux/blk-mq.h>
+#include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/hdreg.h>
 #include <linux/kernel.h>
@@ -32,6 +33,10 @@
 
 #define NVME_MINORS		(1U << MINORBITS)
 
+static unsigned char shutdown_timeout = 5;
+module_param(shutdown_timeout, byte, 0644);
+MODULE_PARM_DESC(shutdown_timeout, "timeout in seconds for controller shutdown");
+
 static int nvme_major;
 module_param(nvme_major, int, 0);
 
@@ -351,6 +356,88 @@ int nvme_set_queue_count(struct nvme_ctrl *ctrl, int count)
 	return min(result & 0xffff, result >> 16) + 1;
 }
 
+static int nvme_update_ctrl_config(struct nvme_ctrl *ctrl, u64 cap,
+		bool enabled)
+{
+	unsigned long timeout =
+		((NVME_CAP_TIMEOUT(cap) + 1) * HZ / 2) + jiffies;
+	u32 bit = enabled ? NVME_CSTS_RDY : 0, csts;
+	int error;
+
+	error = ctrl->ops->reg_write32(ctrl, NVME_REG_CC, ctrl->ctrl_config);
+	if (error)
+		return error;
+
+	while (!(error = ctrl->ops->reg_read32(ctrl, NVME_REG_CSTS, &csts))) {
+		if ((csts & NVME_CSTS_RDY) == bit)
+			break;
+
+		msleep(100);
+		if (fatal_signal_pending(current))
+			return -EINTR;
+		if (time_after(jiffies, timeout)) {
+			dev_err(ctrl->dev,
+				"Controller not ready; aborting %s\n", enabled ?
+						"initialisation" : "reset");
+			return -ENODEV;
+		}
+	}
+
+	return error;
+}
+
+/*
+ * If the device has been passed off to us in an enabled state, just clear
+ * the enabled bit.  The spec says we should set the 'shutdown notification
+ * bits', but doing so may cause the device to complete commands to the
+ * admin queue ... and we don't know what memory that might be pointing at!
+ */
+int nvme_disable_ctrl(struct nvme_ctrl *ctrl, u64 cap)
+{
+	ctrl->ctrl_config &= ~NVME_CC_SHN_MASK;
+	ctrl->ctrl_config &= ~NVME_CC_ENABLE;
+
+	return nvme_update_ctrl_config(ctrl, cap, false);
+}
+
+int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap)
+{
+	ctrl->ctrl_config &= ~NVME_CC_SHN_MASK;
+	ctrl->ctrl_config |= NVME_CC_ENABLE;
+
+	return nvme_update_ctrl_config(ctrl, cap, true);
+}
+
+int nvme_shutdown_ctrl(struct nvme_ctrl *ctrl)
+{
+	unsigned long timeout = (shutdown_timeout * HZ) + jiffies;
+	u32 csts;
+	int error;
+
+	ctrl->ctrl_config &= ~NVME_CC_SHN_MASK;
+	ctrl->ctrl_config |= NVME_CC_SHN_NORMAL;
+
+	error = ctrl->ops->reg_write32(ctrl, NVME_REG_CC, ctrl->ctrl_config);
+	if (error)
+		return error;
+
+	while (!(error = ctrl->ops->reg_read32(ctrl, NVME_REG_CSTS, &csts))) {
+		if ((csts & NVME_CSTS_SHST_MASK) != NVME_CSTS_SHST_CMPLT)
+			break;
+
+		msleep(100);
+		if (fatal_signal_pending(current))
+			return -EINTR;
+		if (time_after(jiffies, timeout)) {
+			dev_err(ctrl->dev,
+				"Device shutdown incomplete; abort shutdown\n");
+			return -ENODEV;
+		}
+	}
+
+	return error;
+}
+
 static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
 {
 	struct nvme_user_io io;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 1692fda..426cafc 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -52,6 +52,7 @@ struct nvme_ctrl {
 	char serial[20];
 	char model[40];
 	char firmware_rev[8];
+	u32 ctrl_config;
 	u32 max_hw_sectors;
 	u32 stripe_size;
 	u32 page_size;
@@ -228,6 +229,9 @@ int nvme_get_features(struct nvme_ctrl *dev, unsigned fid, unsigned nsid,
 int nvme_set_features(struct nvme_ctrl *dev, unsigned fid, unsigned dword11,
 			dma_addr_t dma_addr, u32 *result);
 int nvme_set_queue_count(struct nvme_ctrl *ctrl, int count);
+int nvme_disable_ctrl(struct nvme_ctrl *ctrl, u64 cap);
+int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap);
+int nvme_shutdown_ctrl(struct nvme_ctrl *ctrl);
 
 extern spinlock_t dev_list_lock;
 
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 89d2442..d50a2b7 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -48,7 +48,6 @@
 #define NVME_NR_AEN_COMMANDS	1
 #define SQ_SIZE(depth)		(depth * sizeof(struct nvme_command))
 #define CQ_SIZE(depth)		(depth * sizeof(struct nvme_completion))
-#define SHUTDOWN_TIMEOUT	(shutdown_timeout * HZ)
 
 unsigned char admin_timeout = 60;
 module_param(admin_timeout, byte, 0644);
@@ -58,10 +57,6 @@ unsigned char nvme_io_timeout = 30;
 module_param_named(io_timeout, nvme_io_timeout, byte, 0644);
 MODULE_PARM_DESC(io_timeout, "timeout in seconds for I/O");
 
-static unsigned char shutdown_timeout = 5;
-module_param(shutdown_timeout, byte, 0644);
-MODULE_PARM_DESC(shutdown_timeout, "timeout in seconds for controller shutdown");
-
 static int use_threaded_interrupts;
 module_param(use_threaded_interrupts, int, 0);
 
@@ -105,7 +100,6 @@ struct nvme_dev {
 	unsigned max_qid;
 	int q_depth;
 	u32 db_stride;
-	u32 ctrl_config;
 	struct msix_entry *entry;
 	void __iomem *bar;
 	struct work_struct reset_work;
@@ -1192,77 +1186,6 @@ static int nvme_create_queue(struct nvme_queue *nvmeq, int qid)
 	return result;
 }
 
-static int nvme_wait_ready(struct nvme_dev *dev, u64 cap, bool enabled)
-{
-	unsigned long timeout;
-	u32 bit = enabled ? NVME_CSTS_RDY : 0;
-
-	timeout = ((NVME_CAP_TIMEOUT(cap) + 1) * HZ / 2) + jiffies;
-
-	while ((readl(dev->bar + NVME_REG_CSTS) & NVME_CSTS_RDY) != bit) {
-		msleep(100);
-		if (fatal_signal_pending(current))
-			return -EINTR;
-		if (time_after(jiffies, timeout)) {
-			dev_err(dev->dev,
-				"Device not ready; aborting %s\n", enabled ?
-						"initialisation" : "reset");
-			return -ENODEV;
-		}
-	}
-
-	return 0;
-}
-
-/*
- * If the device has been passed off to us in an enabled state, just clear
- * the enabled bit.  The spec says we should set the 'shutdown notification
- * bits', but doing so may cause the device to complete commands to the
- * admin queue ... and we don't know what memory that might be pointing at!
- */
-static int nvme_disable_ctrl(struct nvme_dev *dev, u64 cap)
-{
-	dev->ctrl_config &= ~NVME_CC_SHN_MASK;
-	dev->ctrl_config &= ~NVME_CC_ENABLE;
-	writel(dev->ctrl_config, dev->bar + NVME_REG_CC);
-
-	return nvme_wait_ready(dev, cap, false);
-}
-
-static int nvme_enable_ctrl(struct nvme_dev *dev, u64 cap)
-{
-	dev->ctrl_config &= ~NVME_CC_SHN_MASK;
-	dev->ctrl_config |= NVME_CC_ENABLE;
-	writel(dev->ctrl_config, dev->bar + NVME_REG_CC);
-
-	return nvme_wait_ready(dev, cap, true);
-}
-
-static int nvme_shutdown_ctrl(struct nvme_dev *dev)
-{
-	unsigned long timeout;
-
-	dev->ctrl_config &= ~NVME_CC_SHN_MASK;
-	dev->ctrl_config |= NVME_CC_SHN_NORMAL;
-
-	writel(dev->ctrl_config, dev->bar + NVME_REG_CC);
-
-	timeout = SHUTDOWN_TIMEOUT + jiffies;
-	while ((readl(dev->bar + NVME_REG_CSTS) & NVME_CSTS_SHST_MASK) !=
-							NVME_CSTS_SHST_CMPLT) {
-		msleep(100);
-		if (fatal_signal_pending(current))
-			return -EINTR;
-		if (time_after(jiffies, timeout)) {
-			dev_err(dev->dev,
-				"Device shutdown incomplete; abort shutdown\n");
-			return -ENODEV;
-		}
-	}
-
-	return 0;
-}
-
 static struct blk_mq_ops nvme_mq_admin_ops = {
 	.queue_rq	= nvme_queue_rq,
 	.complete	= nvme_complete_rq,
@@ -1353,7 +1276,7 @@ static int nvme_configure_admin_queue(struct nvme_dev *dev)
 	    (readl(dev->bar + NVME_REG_CSTS) & NVME_CSTS_NSSRO))
 		writel(NVME_CSTS_NSSRO, dev->bar + NVME_REG_CSTS);
 
-	result = nvme_disable_ctrl(dev, cap);
+	result = nvme_disable_ctrl(&dev->ctrl, cap);
 	if (result < 0)
 		return result;
 
@@ -1369,16 +1292,16 @@ static int nvme_configure_admin_queue(struct nvme_dev *dev)
 
 	dev->page_size = 1 << page_shift;
 
-	dev->ctrl_config = NVME_CC_CSS_NVM;
-	dev->ctrl_config |= (page_shift - 12) << NVME_CC_MPS_SHIFT;
-	dev->ctrl_config |= NVME_CC_ARB_RR | NVME_CC_SHN_NONE;
-	dev->ctrl_config |= NVME_CC_IOSQES | NVME_CC_IOCQES;
+	dev->ctrl.ctrl_config = NVME_CC_CSS_NVM;
+	dev->ctrl.ctrl_config |= (page_shift - 12) << NVME_CC_MPS_SHIFT;
+	dev->ctrl.ctrl_config |= NVME_CC_ARB_RR | NVME_CC_SHN_NONE;
+	dev->ctrl.ctrl_config |= NVME_CC_IOSQES | NVME_CC_IOCQES;
 
 	writel(aqa, dev->bar + NVME_REG_AQA);
 	writeq(nvmeq->sq_dma_addr, dev->bar + NVME_REG_ASQ);
 	writeq(nvmeq->cq_dma_addr, dev->bar + NVME_REG_ACQ);
 
-	result = nvme_enable_ctrl(dev, cap);
+	result = nvme_enable_ctrl(&dev->ctrl, cap);
 	if (result)
 		goto free_nvmeq;
 
@@ -1764,7 +1687,8 @@ static void nvme_wait_dq(struct nvme_delq_ctx *dq, struct nvme_dev *dev)
 			 * queues than admin tags.
 			 */
 			set_current_state(TASK_RUNNING);
-			nvme_disable_ctrl(dev, readq(dev->bar + NVME_REG_CAP));
+			nvme_disable_ctrl(&dev->ctrl,
+				readq(dev->bar + NVME_REG_CAP));
 			nvme_clear_queue(dev->queues[0]);
 			flush_kthread_worker(dq->worker);
 			nvme_disable_queue(dev, 0);
@@ -1977,7 +1901,7 @@ static void nvme_dev_shutdown(struct nvme_dev *dev)
 		}
 	} else {
 		nvme_disable_io_queues(dev);
-		nvme_shutdown_ctrl(dev);
+		nvme_shutdown_ctrl(&dev->ctrl);
 		nvme_disable_queue(dev, 0);
 	}
 	nvme_dev_unmap(dev);
-- 
1.9.1

[PATCH 2/8] nvme: move enable/disable/shutdown_ctrl to common code

[Sagi Grimberg]

Maybe it'd be better to split this to two patches.
1. pass ctrl to enable/disable/shutdown_ctrl
2. move enable/disable/shutdown_ctrl to common code

Other then that looks good.

[PATCH 2/8] nvme: move enable/disable/shutdown_ctrl to common code

[Christoph Hellwig]

On Sun, Nov 08, 2015@06:39:57PM +0200, Sagi Grimberg wrote:
> Maybe it'd be better to split this to two patches.
> 1. pass ctrl to enable/disable/shutdown_ctrl
> 2. move enable/disable/shutdown_ctrl to common code
>
> Other then that looks good.

I haven't really done that for any of the previous split patches either
as it sees a bit confusing.

[PATCH 3/8] nvme: move CC setup into nvme_enable_ctrl

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/nvme/host/core.c | 7 +++++--
 drivers/nvme/host/nvme.h | 2 +-
 drivers/nvme/host/pci.c  | 7 +------
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index c061a6a..2254ce9 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -400,9 +400,12 @@ int nvme_disable_ctrl(struct nvme_ctrl *ctrl, u64 cap)
 	return nvme_update_ctrl_config(ctrl, cap, false);
 }
 
-int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap)
+int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap, unsigned page_shift)
 {
-	ctrl->ctrl_config &= ~NVME_CC_SHN_MASK;
+	ctrl->ctrl_config = NVME_CC_CSS_NVM;
+	ctrl->ctrl_config |= (page_shift - 12) << NVME_CC_MPS_SHIFT;
+	ctrl->ctrl_config |= NVME_CC_ARB_RR | NVME_CC_SHN_NONE;
+	ctrl->ctrl_config |= NVME_CC_IOSQES | NVME_CC_IOCQES;
 	ctrl->ctrl_config |= NVME_CC_ENABLE;
 
 	return nvme_update_ctrl_config(ctrl, cap, true);
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 426cafc..8cf6fa5 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -230,7 +230,7 @@ int nvme_set_features(struct nvme_ctrl *dev, unsigned fid, unsigned dword11,
 			dma_addr_t dma_addr, u32 *result);
 int nvme_set_queue_count(struct nvme_ctrl *ctrl, int count);
 int nvme_disable_ctrl(struct nvme_ctrl *ctrl, u64 cap);
-int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap);
+int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap, unsigned page_shift);
 int nvme_shutdown_ctrl(struct nvme_ctrl *ctrl);
 
 extern spinlock_t dev_list_lock;
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index d50a2b7..45255e3 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1292,16 +1292,11 @@ static int nvme_configure_admin_queue(struct nvme_dev *dev)
 
 	dev->page_size = 1 << page_shift;
 
-	dev->ctrl.ctrl_config = NVME_CC_CSS_NVM;
-	dev->ctrl.ctrl_config |= (page_shift - 12) << NVME_CC_MPS_SHIFT;
-	dev->ctrl.ctrl_config |= NVME_CC_ARB_RR | NVME_CC_SHN_NONE;
-	dev->ctrl.ctrl_config |= NVME_CC_IOSQES | NVME_CC_IOCQES;
-
 	writel(aqa, dev->bar + NVME_REG_AQA);
 	writeq(nvmeq->sq_dma_addr, dev->bar + NVME_REG_ASQ);
 	writeq(nvmeq->cq_dma_addr, dev->bar + NVME_REG_ACQ);
 
-	result = nvme_enable_ctrl(&dev->ctrl, cap);
+	result = nvme_enable_ctrl(&dev->ctrl, cap, page_shift);
 	if (result)
 		goto free_nvmeq;
 
-- 
1.9.1

[PATCH 4/8] nvme: move the timeout module paramters to common code

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/nvme/host/core.c | 8 ++++++++
 drivers/nvme/host/pci.c  | 8 --------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 2254ce9..6737aaf 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -33,6 +33,14 @@
 
 #define NVME_MINORS		(1U << MINORBITS)
 
+unsigned char admin_timeout = 60;
+module_param(admin_timeout, byte, 0644);
+MODULE_PARM_DESC(admin_timeout, "timeout in seconds for admin commands");
+
+unsigned char nvme_io_timeout = 30;
+module_param_named(io_timeout, nvme_io_timeout, byte, 0644);
+MODULE_PARM_DESC(io_timeout, "timeout in seconds for I/O");
+
 static unsigned char shutdown_timeout = 5;
 module_param(shutdown_timeout, byte, 0644);
 MODULE_PARM_DESC(shutdown_timeout, "timeout in seconds for controller shutdown");
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 45255e3..91522bb 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -49,14 +49,6 @@
 #define SQ_SIZE(depth)		(depth * sizeof(struct nvme_command))
 #define CQ_SIZE(depth)		(depth * sizeof(struct nvme_completion))
 
-unsigned char admin_timeout = 60;
-module_param(admin_timeout, byte, 0644);
-MODULE_PARM_DESC(admin_timeout, "timeout in seconds for admin commands");
-
-unsigned char nvme_io_timeout = 30;
-module_param_named(io_timeout, nvme_io_timeout, byte, 0644);
-MODULE_PARM_DESC(io_timeout, "timeout in seconds for I/O");
-
 static int use_threaded_interrupts;
 module_param(use_threaded_interrupts, int, 0);
 
-- 
1.9.1

[PATCH 5/8] nvme: add segment limitations

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/nvme/host/core.c | 11 +++++++++--
 drivers/nvme/host/nvme.h |  2 ++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 6737aaf..14ee152 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -982,9 +982,16 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
 	blk_queue_logical_block_size(ns->queue, 1 << ns->lba_shift);
 	if (ctrl->max_hw_sectors) {
 		blk_queue_max_hw_sectors(ns->queue, ctrl->max_hw_sectors);
-		blk_queue_max_segments(ns->queue,
-			((ctrl->max_hw_sectors << 9) / ctrl->page_size) + 1);
+
+		if (!ctrl->max_segments)
+			ctrl->max_segments = ((ctrl->max_hw_sectors << 9) /
+						ctrl->page_size) + 1;
 	}
+
+	if (ctrl->max_segments)
+		blk_queue_max_segments(ns->queue, ctrl->max_segments);
+	if (ctrl->max_segment_size)
+		blk_queue_max_segment_size(ns->queue, ctrl->max_segment_size);
 	if (ctrl->stripe_size)
 		blk_queue_chunk_sectors(ns->queue, ctrl->stripe_size >> 9);
 	if (ctrl->vwc & NVME_CTRL_VWC_PRESENT)
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 8cf6fa5..8377a3f 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -55,6 +55,8 @@ struct nvme_ctrl {
 	u32 ctrl_config;
 	u32 max_hw_sectors;
 	u32 stripe_size;
+	u32 max_segments;
+	u32 max_segment_size;
 	u32 page_size;
 	u16 oncs;
 	atomic_t abort_limit;
-- 
1.9.1

[PATCH 6/8] nvme: export symbols needed for nvme-loop

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/nvme/host/core.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 14ee152..400b1ea 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -36,10 +36,12 @@
 unsigned char admin_timeout = 60;
 module_param(admin_timeout, byte, 0644);
 MODULE_PARM_DESC(admin_timeout, "timeout in seconds for admin commands");
+EXPORT_SYMBOL_GPL(admin_timeout);
 
 unsigned char nvme_io_timeout = 30;
 module_param_named(io_timeout, nvme_io_timeout, byte, 0644);
 MODULE_PARM_DESC(io_timeout, "timeout in seconds for I/O");
+EXPORT_SYMBOL_GPL(nvme_io_timeout);
 
 static unsigned char shutdown_timeout = 5;
 module_param(shutdown_timeout, byte, 0644);
@@ -97,6 +99,7 @@ void nvme_requeue_req(struct request *req)
 		blk_mq_kick_requeue_list(req->q);
 	spin_unlock_irqrestore(req->q->queue_lock, flags);
 }
+EXPORT_SYMBOL_GPL(nvme_requeue_req);
 
 struct request *nvme_alloc_request(struct request_queue *q,
 		struct nvme_command *cmd, bool nowait)
@@ -324,6 +327,7 @@ int nvme_set_features(struct nvme_ctrl *dev, unsigned fid, unsigned dword11,
 
 	return __nvme_submit_sync_cmd(dev->admin_q, &c, NULL, 0, result, 0);
 }
+EXPORT_SYMBOL_GPL(nvme_set_features);
 
 int nvme_get_log_page(struct nvme_ctrl *dev, struct nvme_smart_log **log)
 {
@@ -363,6 +367,7 @@ int nvme_set_queue_count(struct nvme_ctrl *ctrl, int count)
 	}
 	return min(result & 0xffff, result >> 16) + 1;
 }
+EXPORT_SYMBOL_GPL(nvme_set_queue_count);
 
 static int nvme_update_ctrl_config(struct nvme_ctrl *ctrl, u64 cap,
 		bool enabled)
@@ -407,6 +412,7 @@ int nvme_disable_ctrl(struct nvme_ctrl *ctrl, u64 cap)
 
 	return nvme_update_ctrl_config(ctrl, cap, false);
 }
+EXPORT_SYMBOL_GPL(nvme_disable_ctrl);
 
 int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap, unsigned page_shift)
 {
@@ -418,6 +424,7 @@ int nvme_enable_ctrl(struct nvme_ctrl *ctrl, u64 cap, unsigned page_shift)
 
 	return nvme_update_ctrl_config(ctrl, cap, true);
 }
+EXPORT_SYMBOL_GPL(nvme_enable_ctrl);
 
 int nvme_shutdown_ctrl(struct nvme_ctrl *ctrl)
 {
@@ -448,6 +455,7 @@ int nvme_shutdown_ctrl(struct nvme_ctrl *ctrl)
 
 	return error;
 }
+EXPORT_SYMBOL_GPL(nvme_shutdown_ctrl);
 
 static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
 {
@@ -851,6 +859,7 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 	kfree(id);
 	return 0;
 }
+EXPORT_SYMBOL(nvme_init_identify);
 
 static int nvme_dev_open(struct inode *inode, struct file *file)
 {
@@ -1071,6 +1080,7 @@ void nvme_scan_namespaces(struct nvme_ctrl *ctrl)
 	__nvme_scan_namespaces(ctrl, le32_to_cpup(&id->nn));
 	kfree(id);
 }
+EXPORT_SYMBOL_GPL(nvme_scan_namespaces);
 
 void nvme_remove_namespaces(struct nvme_ctrl *ctrl)
 {
@@ -1079,6 +1089,7 @@ void nvme_remove_namespaces(struct nvme_ctrl *ctrl)
 	list_for_each_entry_safe(ns, next, &ctrl->namespaces, list)
 		nvme_ns_remove(ns);
 }
+EXPORT_SYMBOL_GPL(nvme_remove_namespaces);
 
 static DEFINE_IDA(nvme_instance_ida);
 
@@ -1118,6 +1129,7 @@ void nvme_uninit_ctrl(struct nvme_ctrl *ctrl)
 	list_del(&ctrl->node);
 	spin_unlock(&dev_list_lock);
 }
+EXPORT_SYMBOL_GPL(nvme_uninit_ctrl);
 
 static void nvme_free_ctrl(struct kref *kref)
 {
@@ -1133,6 +1145,7 @@ void nvme_put_ctrl(struct nvme_ctrl *ctrl)
 {
 	kref_put(&ctrl->kref, nvme_free_ctrl);
 }
+EXPORT_SYMBOL_GPL(nvme_put_ctrl);
 
 /*
  * Initialize a NVMe controller structures.  This needs to be called during
@@ -1184,6 +1197,7 @@ out_release_instance:
 out:
 	return ret;
 }
+EXPORT_SYMBOL_GPL(nvme_init_ctrl);
 
 int __init nvme_core_init(void)
 {
-- 
1.9.1

[PATCH 7/8] nvmet: add a generic NVMe target

[Christoph Hellwig]

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/nvme/Kconfig            |   1 +
 drivers/nvme/Makefile           |   1 +
 drivers/nvme/target/Kconfig     |   4 +
 drivers/nvme/target/Makefile    |   4 +
 drivers/nvme/target/admin-cmd.c | 353 +++++++++++++++++++++++++++++++
 drivers/nvme/target/configfs.c  | 205 ++++++++++++++++++
 drivers/nvme/target/core.c      | 454 ++++++++++++++++++++++++++++++++++++++++
 drivers/nvme/target/io-cmd.c    | 114 ++++++++++
 drivers/nvme/target/nvmet.h     | 172 +++++++++++++++
 9 files changed, 1308 insertions(+)
 create mode 100644 drivers/nvme/target/Kconfig
 create mode 100644 drivers/nvme/target/Makefile
 create mode 100644 drivers/nvme/target/admin-cmd.c
 create mode 100644 drivers/nvme/target/configfs.c
 create mode 100644 drivers/nvme/target/core.c
 create mode 100644 drivers/nvme/target/io-cmd.c
 create mode 100644 drivers/nvme/target/nvmet.h

diff --git a/drivers/nvme/Kconfig b/drivers/nvme/Kconfig
index a39d943..b7c78a5 100644
--- a/drivers/nvme/Kconfig
+++ b/drivers/nvme/Kconfig
@@ -1 +1,2 @@
 source "drivers/nvme/host/Kconfig"
+source "drivers/nvme/target/Kconfig"
diff --git a/drivers/nvme/Makefile b/drivers/nvme/Makefile
index 9421e82..0096a7f 100644
--- a/drivers/nvme/Makefile
+++ b/drivers/nvme/Makefile
@@ -1,2 +1,3 @@
 
 obj-y		+= host/
+obj-y		+= target/
diff --git a/drivers/nvme/target/Kconfig b/drivers/nvme/target/Kconfig
new file mode 100644
index 0000000..9a3d742
--- /dev/null
+++ b/drivers/nvme/target/Kconfig
@@ -0,0 +1,4 @@
+
+config NVME_TARGET
+	depends on BLOCK
+	tristate
diff --git a/drivers/nvme/target/Makefile b/drivers/nvme/target/Makefile
new file mode 100644
index 0000000..9c236e4
--- /dev/null
+++ b/drivers/nvme/target/Makefile
@@ -0,0 +1,4 @@
+
+obj-$(CONFIG_NVME_TARGET)		+= nvmet.o
+
+nvmet-y		+= core.o configfs.o admin-cmd.o io-cmd.o
diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
new file mode 100644
index 0000000..d9db0d4
--- /dev/null
+++ b/drivers/nvme/target/admin-cmd.c
@@ -0,0 +1,353 @@
+/*
+ * Copyright (c) 2015 HGST, a Western Digital Company.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/blkdev.h>
+#include <linux/module.h>
+#include "nvmet.h"
+
+static void nvmet_execute_get_error_log(struct nvmet_req *req)
+{
+	void *buf;
+
+	/*
+	 * We currently never set the More bit in the status field,
+	 * so all error log entries are invalid and can be zeroed out.
+	 * This is called a minum viable implementation (TM) of this
+	 * mandatory log page.
+	 */
+	buf = kmap_atomic(sg_page(req->sg)) + req->sg->offset;
+	memset(buf, 0, req->data_len);
+	kunmap_atomic(buf);
+
+	nvmet_req_complete(req, 0);
+}
+
+static void nvmet_execute_get_smart_log(struct nvmet_req *req)
+{
+	struct nvme_smart_log *log;
+
+	/*
+	 * XXX: fill out actual smart log
+	 *
+	 * We might have a hard time coming up with useful values for many
+	 * of the fields, and even when we have useful data available
+	 * (e.g. units or commands read/written) those aren't persistent
+	 * over power loss.
+	 */
+	log = kmap_atomic(sg_page(req->sg)) + req->sg->offset;
+	memset(log, 0, req->data_len);
+	kunmap_atomic(log);
+
+	nvmet_req_complete(req, 0);
+}
+
+static void nvmet_execute_get_fwslot_log(struct nvmet_req *req)
+{
+	void *buf;
+
+	/*
+	 * We only support a single firmware slot which always is active,
+	 * so we can zero out the whole firmware slot log and still claim
+	 * to fully implement this mandatory log page.
+	 */
+	buf = kmap_atomic(sg_page(req->sg)) + req->sg->offset;
+	memset(buf, 0, req->data_len);
+	kunmap_atomic(buf);
+
+	nvmet_req_complete(req, 0);
+}
+
+static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
+{
+	struct nvmet_ctrl *ctrl = req->sq->ctrl;
+	struct nvme_id_ctrl *id;
+
+	id = kmap_atomic(sg_page(req->sg)) + req->sg->offset;
+	memset(id, 0, sizeof(*id));
+
+	/* XXX: figure out how to assign real vendors IDs. */
+	id->vid = 0;
+	id->ssvid = 0;
+
+	/* XXX: figure out real serial / model / revision values */
+	memset(id->sn, ' ', sizeof(id->sn));
+	memset(id->mn, ' ', sizeof(id->mn));
+	memset(id->fr, ' ', sizeof(id->fr));
+	strcpy((char *)id->mn, "Fake NVMe");
+
+	id->rab = 6;
+
+	/* XXX: figure out a real IEEE OUI */
+	id->ieee[0] = 0x00;
+	id->ieee[1] = 0x02;
+	id->ieee[2] = 0xb3;
+
+	/* we may have multiple controllers attached to the subsystem */
+	id->mic = (1 << 1);
+
+	/* no limit on data transfer sizes for now */
+	id->mdts = 0;
+	id->cntlid = cpu_to_le16(ctrl->cntlid);
+	id->ver = cpu_to_le32(ctrl->subsys->ver);
+
+	/* XXX: figure out what to do about RTD3R/RTD3 */
+
+	id->oacs = 0;
+	id->acl = 3;
+	id->aerl = 3;
+
+	/* first slot is read-only, only one slot supported */
+	id->frmw = (1 << 0) | (1 << 1);
+	id->lpa = 1 << 0;
+#define NVMET_ERROR_LOG_SLOTS	128
+	id->elpe = NVMET_ERROR_LOG_SLOTS - 1;
+	id->npss = 0;
+
+	id->sqes = (0x6 << 4) | 0x6;
+	id->cqes = (0x4 << 4) | 0x4;
+	id->nn = cpu_to_le32(ctrl->subsys->max_nsid);
+
+	/* XXX: don't report vwc if the underlying device is write through */
+	id->vwc = NVME_CTRL_VWC_PRESENT;
+
+	/*
+	 * We can't support atomic writes bigger than a LBA without support
+	 * from the backend device.
+	 */
+	id->awun = 0;
+	id->awupf = 0;
+
+	/*
+	 * We support SGLs, but nothing fancy.
+	 */
+	id->sgls = (1 << 0);
+
+	/*
+	 * Meh, we don't really support any power state.  Fake up the same
+	 * values that qemu does.
+	 */
+	id->psd[0].max_power = cpu_to_le16(0x9c4);
+	id->psd[0].entry_lat = cpu_to_le32(0x10);
+	id->psd[0].exit_lat = cpu_to_le32(0x4);
+
+	kunmap_atomic(id);
+
+	nvmet_req_complete(req, 0);
+}
+
+static void nvmet_execute_identify_ns(struct nvmet_req *req)
+{
+	struct nvmet_ns *ns;
+	struct nvme_id_ns *id;
+	u16 status = 0;
+
+	ns = nvmet_find_namespace(req->sq->ctrl, req->cmd->identify.nsid);
+	if (!ns) {
+		status = NVME_SC_INVALID_NS | NVME_SC_DNR;
+		goto out;
+	}
+
+	id = kmap_atomic(sg_page(req->sg)) + req->sg->offset;
+	memset(id, 0, sizeof(*id));
+
+	/*
+	 * nuse = ncap = nsze isn't aways true, but we have no way to find
+	 * that out from the underlying device.
+	 */
+	id->ncap = id->nuse = id->nsze =
+		cpu_to_le64(ns->size >> ns->blksize_shift);
+
+	/*
+	 * We just provide a single LBA format that matches what the
+	 * underlying device reports.
+	 */
+	id->nlbaf = 0;
+	id->flbas = 0;
+
+	/*
+	 * Our namespace might always be shared.  Not just with other
+	 * controllers, but also with any other user of the block device.
+	 */
+	id->nmic = (1 << 0);
+
+	/* XXX: provide a nguid value! */
+
+	id->lbaf[0].ds = ns->blksize_shift;
+
+	kunmap_atomic(id);
+
+	nvmet_put_namespace(ns);
+out:
+	nvmet_req_complete(req, status);
+}
+
+static void nvmet_execute_identify_nslist(struct nvmet_req *req)
+{
+	struct nvmet_ctrl *ctrl = req->sq->ctrl;
+	struct nvmet_ns *ns;
+	u32 min_nsid = le32_to_cpu(req->cmd->identify.nsid);
+	__le32 *list;
+	int i = 0;
+
+	list = kmap_atomic(sg_page(req->sg)) + req->sg->offset;
+	rcu_read_lock();
+	list_for_each_entry_rcu(ns, &ctrl->subsys->namespaces, dev_link) {
+		if (ns->nsid <= min_nsid)
+			continue;
+		list[i++] = cpu_to_le32(ns->nsid);
+		if (i == req->data_len / sizeof(__le32))
+			goto out;
+	}
+
+	list[i] = 0;
+out:
+	rcu_read_unlock();
+	kunmap_atomic(list);
+
+	nvmet_req_complete(req, 0);
+}
+
+static void nvmet_execute_set_features(struct nvmet_req *req)
+{
+	struct nvmet_subsys *subsys = req->sq->ctrl->subsys;
+	u32 cdw10 = le32_to_cpu(req->cmd->common.cdw10[0]);
+	u16 status = 0;
+
+	switch (cdw10 & 0xf) {
+	case NVME_FEAT_NUM_QUEUES:
+		nvmet_set_result(req,
+			subsys->max_qid | (subsys->max_qid << 16));
+		break;
+	default:
+		status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
+		break;
+	}
+
+	nvmet_req_complete(req, status);
+}
+
+static void nvmet_execute_get_features(struct nvmet_req *req)
+{
+	struct nvmet_subsys *subsys = req->sq->ctrl->subsys;
+	u32 cdw10 = le32_to_cpu(req->cmd->common.cdw10[0]);
+	u16 status = 0;
+
+	switch (cdw10 & 0xf) {
+	/*
+	 * These features are mandatory in the spec, but we don't
+	 * have a useful way to implement them.  We'll eventually
+	 * need to come up with some fake values for these.
+	 */
+#if 0
+	case NVME_FEAT_ARBITRATION:
+		break;
+	case NVME_FEAT_POWER_MGMT:
+		break;
+	case NVME_FEAT_TEMP_THRESH:
+		break;
+	case NVME_FEAT_ERR_RECOVERY:
+		break;
+	case NVME_FEAT_IRQ_COALESCE:
+		break;
+	case NVME_FEAT_IRQ_CONFIG:
+		break;
+	case NVME_FEAT_WRITE_ATOMIC:
+		break;
+	case NVME_FEAT_ASYNC_EVENT:
+		break;
+#endif
+	case NVME_FEAT_VOLATILE_WC:
+		nvmet_set_result(req, 1);
+		break;
+	case NVME_FEAT_NUM_QUEUES:
+		nvmet_set_result(req,
+			subsys->max_qid | (subsys->max_qid << 16));
+		break;
+	default:
+		status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
+		break;
+	}
+
+	nvmet_req_complete(req, status);
+}
+
+static inline u32 nvmet_get_log_page_len(struct nvme_command *cmd)
+{
+	u32 cdw10 = cmd->common.cdw10[0];
+
+	return ((cdw10 >> 16) & 0xff) * sizeof(u32);
+}
+
+int nvmet_parse_admin_cmd(struct nvmet_req *req)
+{
+	struct nvme_command *cmd = req->cmd;
+
+	req->ns = NULL;
+
+	switch (cmd->common.opcode) {
+	case nvme_admin_get_log_page:
+		req->data_len = nvmet_get_log_page_len(cmd);
+
+		switch (cmd->common.cdw10[0] & 0xf) {
+		case 0x01:
+			req->execute = nvmet_execute_get_error_log;
+			return 0;
+		case 0x02:
+			req->execute = nvmet_execute_get_smart_log;
+			return 0;
+		case 0x03:
+			req->execute = nvmet_execute_get_fwslot_log;
+			return 0;
+		}
+		break;
+	case nvme_admin_identify:
+		switch (cmd->identify.cns) {
+		case 0x00:
+			req->execute = nvmet_execute_identify_ns;
+			req->data_len = sizeof(struct nvme_id_ns);
+			return 0;
+		case 0x01:
+			req->execute = nvmet_execute_identify_ctrl;
+			req->data_len = sizeof(struct nvme_id_ctrl);
+			return 0;
+		case 0x02:
+			req->execute = nvmet_execute_identify_nslist;
+			req->data_len = 4096;
+			return 0;
+		}
+		break;
+#if 0
+	case nvme_admin_abort_cmd:
+		req->execute = nvmet_execute_abort;
+		req->data_len = 0;
+		return 0;
+#endif
+	case nvme_admin_set_features:
+		req->execute = nvmet_execute_set_features;
+		req->data_len = 0;
+		return 0;
+	case nvme_admin_get_features:
+		req->execute = nvmet_execute_get_features;
+		req->data_len = 0;
+		return 0;
+#if 0
+	case nvme_admin_async_event:
+		req->exectute = nvmet_execute_aen;
+		req->data = 0;
+		return 0;
+#endif
+	}
+
+	pr_err("nvmet: unhandled cmd %d\n", cmd->common.opcode);
+	return NVME_SC_INVALID_OPCODE | NVME_SC_DNR;
+}
diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
new file mode 100644
index 0000000..7dcdc58e
--- /dev/null
+++ b/drivers/nvme/target/configfs.c
@@ -0,0 +1,205 @@
+/*
+ * Copyright (c) 2015 HGST, a Western Digital Company.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/stat.h>
+
+#include "nvmet.h"
+
+
+CONFIGFS_ATTR_STRUCT(nvmet_ns);
+CONFIGFS_ATTR_OPS(nvmet_ns);
+
+static ssize_t nvmet_ns_device_path_show(struct nvmet_ns *ns, char *page)
+{
+	return sprintf(page, "%s", ns->device_path);
+}
+
+static ssize_t nvmet_ns_device_path_store(struct nvmet_ns *ns, const char *page,
+		size_t count)
+{
+	int ret = nvmet_ns_enable(ns, page);
+
+	return ret ? ret : count;
+}
+
+static struct nvmet_ns_attribute nvmet_ns_attr_device_path = {
+	.attr = {
+		.ca_name	= "device_path",
+		.ca_mode	= S_IRUSR | S_IWUSR,
+		.ca_owner	= THIS_MODULE,
+	},
+	.show			= nvmet_ns_device_path_show,
+	.store			= nvmet_ns_device_path_store,
+};
+
+static struct configfs_attribute *nvmet_ns_attrs[] = {
+	&nvmet_ns_attr_device_path.attr,
+	NULL,
+};
+
+static void nvmet_ns_release(struct config_item *item)
+{
+	struct nvmet_ns *ns = to_nvmet_ns(item);
+
+	nvmet_ns_free(ns);
+}
+
+static struct configfs_item_operations nvmet_ns_item_ops = {
+	.release		= nvmet_ns_release,
+	.show_attribute		= nvmet_ns_attr_show,
+	.store_attribute        = nvmet_ns_attr_store,
+};
+
+static struct config_item_type nvmet_ns_type = {
+	.ct_item_ops		= &nvmet_ns_item_ops,
+	.ct_attrs		= nvmet_ns_attrs,
+	.ct_owner		= THIS_MODULE,
+};
+
+static struct config_group *nvmet_ns_make(struct config_group *group,
+		const char *name)
+{
+	struct nvmet_subsys *subsys = namespaces_to_subsys(&group->cg_item);
+	struct nvmet_ns *ns;
+	int ret;
+	u32 nsid;
+
+	ret = kstrtou32(name, 0, &nsid);
+	if (ret)
+		goto out;
+
+	ret = -EINVAL;
+	if (nsid == 0 || nsid == 0xffffffff)
+		goto out;
+
+	ret = -ENOMEM;
+	ns = nvmet_ns_alloc(subsys, nsid);
+	if (!ns)
+		goto out;
+	config_group_init_type_name(&ns->group, name, &nvmet_ns_type);
+
+	pr_info("adding nsid %d to subsystem %s\n", nsid, subsys->subsys_name);
+
+	return &ns->group;
+out:
+	return ERR_PTR(ret);
+}
+
+static struct configfs_group_operations nvmet_namespaces_group_ops = {
+	.make_group		= nvmet_ns_make,
+};
+
+static struct config_item_type nvmet_namespaces_type = {
+	.ct_group_ops		= &nvmet_namespaces_group_ops,
+	.ct_owner		= THIS_MODULE,
+};
+
+static struct config_item_type nvmet_controllers_type = {
+	.ct_owner		= THIS_MODULE,
+};
+
+static void nvmet_subsys_release(struct config_item *item)
+{
+	struct nvmet_subsys *subsys = to_subsys(item);
+
+	nvmet_subsys_free(subsys);
+}
+
+static struct configfs_item_operations nvmet_subsys_item_ops = {
+	.release		= nvmet_subsys_release,
+};
+
+static struct config_item_type nvmet_subsys_type = {
+	.ct_item_ops		= &nvmet_subsys_item_ops,
+	.ct_owner		= THIS_MODULE,
+};
+
+static struct config_group *nvmet_subsys_make(struct config_group *group,
+		const char *name)
+{
+	struct nvmet_subsys *subsys;
+
+	subsys = nvmet_subsys_alloc(name);
+	if (!subsys)
+		return ERR_PTR(-ENOMEM);
+
+	config_group_init_type_name(&subsys->group, name, &nvmet_subsys_type);
+
+	config_group_init_type_name(&subsys->namespaces_group,
+			"namespaces", &nvmet_namespaces_type);
+	config_group_init_type_name(&subsys->controllers_group,
+			"controllers", &nvmet_controllers_type);
+
+	subsys->default_groups[0] = &subsys->namespaces_group;
+	subsys->default_groups[1] = &subsys->controllers_group;
+	subsys->default_groups[2] = NULL;
+
+	subsys->group.default_groups = subsys->default_groups;
+	return &subsys->group;
+}
+
+static struct configfs_group_operations nvmet_subsystems_group_ops = {
+	.make_group		= nvmet_subsys_make,
+};
+
+static struct config_item_type nvmet_subsystems_type = {
+	.ct_group_ops		= &nvmet_subsystems_group_ops,
+	.ct_owner		= THIS_MODULE,
+};
+
+struct config_group nvmet_subsystems_group;
+
+struct config_group *nvmet_root_default_groups[] = {
+	&nvmet_subsystems_group,
+	NULL,
+};
+
+static struct config_item_type nvmet_root_type = {
+	.ct_owner		= THIS_MODULE,
+};
+
+static struct configfs_subsystem nvmet_configfs_subsystem = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf	= "nvmet",
+			.ci_type	= &nvmet_root_type,
+		},
+		.default_groups = nvmet_root_default_groups,
+	},
+};
+
+int __init nvmet_init_configfs(void)
+{
+	int ret;
+
+	config_group_init(&nvmet_configfs_subsystem.su_group);
+	mutex_init(&nvmet_configfs_subsystem.su_mutex);
+
+	config_group_init_type_name(&nvmet_subsystems_group,
+			"subsystems", &nvmet_subsystems_type);
+
+	ret = configfs_register_subsystem(&nvmet_configfs_subsystem);
+	if (ret) {
+		pr_err("configfs_register_subsystem: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+void __exit nvmet_exit_configfs(void)
+{
+	configfs_unregister_subsystem(&nvmet_configfs_subsystem);
+}
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
new file mode 100644
index 0000000..5c770bf
--- /dev/null
+++ b/drivers/nvme/target/core.c
@@ -0,0 +1,454 @@
+/*
+ * Copyright (c) 2015 HGST, a Western Digital Company.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/blkdev.h>
+#include <linux/module.h>
+#include "nvmet.h"
+
+static DEFINE_MUTEX(nvmet_subsystem_mutex);
+static LIST_HEAD(nvmet_subsystems);
+
+static struct nvmet_ns *__nvmet_find_namespace(struct nvmet_ctrl *ctrl,
+		__le32 nsid)
+{
+	struct nvmet_ns *ns;
+
+	list_for_each_entry_rcu(ns, &ctrl->subsys->namespaces, dev_link) {
+		if (ns->nsid == le32_to_cpu(nsid))
+			return ns;
+	}
+
+	return NULL;
+}
+
+struct nvmet_ns *nvmet_find_namespace(struct nvmet_ctrl *ctrl, __le32 nsid)
+{
+	struct nvmet_ns *ns;
+
+	rcu_read_lock();
+	ns = __nvmet_find_namespace(ctrl, nsid);
+	if (ns && !kref_get_unless_zero(&ns->ref))
+		ns = NULL;
+	rcu_read_unlock();
+
+	return ns;
+}
+
+static void nvmet_destroy_namespace(struct kref *ref)
+{
+	struct nvmet_ns *ns = container_of(ref, struct nvmet_ns, ref);
+
+	if (ns->bdev)
+		blkdev_put(ns->bdev, FMODE_WRITE|FMODE_READ);
+	kfree(ns->device_path);
+	kfree(ns);
+}
+
+void nvmet_put_namespace(struct nvmet_ns *ns)
+{
+	kref_put(&ns->ref, nvmet_destroy_namespace);
+}
+
+int nvmet_ns_enable(struct nvmet_ns *ns, const char *path)
+{
+	int ret;
+
+	mutex_lock(&ns->subsys->lock);
+	ret = -EBUSY;
+	if (ns->device_path)
+		goto out_unlock;
+
+	ret = -ENOMEM;
+	ns->device_path = kstrdup(path, GFP_KERNEL);
+	if (!ns->device_path)
+		goto out_unlock;
+
+	ns->bdev = blkdev_get_by_path(path, FMODE_READ|FMODE_WRITE, NULL);
+	if (IS_ERR(ns->bdev)) {
+		pr_err("nvmet: failed to open block device %s: (%ld)\n",
+			path, PTR_ERR(ns->bdev));
+		ret = PTR_ERR(ns->bdev);
+		goto out_free_device_path;
+	}
+
+	ns->size = i_size_read(ns->bdev->bd_inode);
+	ns->blksize_shift = blksize_bits(bdev_logical_block_size(ns->bdev));
+
+	if (ns->nsid > ns->subsys->max_nsid)
+		ns->subsys->max_nsid = ns->nsid;
+
+	list_add_rcu(&ns->dev_link, &ns->subsys->namespaces);
+	mutex_unlock(&ns->subsys->lock);
+
+	return 0;
+
+out_free_device_path:
+	kfree(ns->device_path);
+	ns->device_path = NULL;
+out_unlock:
+	mutex_unlock(&ns->subsys->lock);
+	return ret;
+}
+
+void nvmet_ns_free(struct nvmet_ns *ns)
+{
+	struct nvmet_subsys *subsys = ns->subsys;
+
+	mutex_lock(&subsys->lock);
+	if (!list_empty(&ns->dev_link))
+		list_del_init(&ns->dev_link);
+	mutex_unlock(&subsys->lock);
+
+	nvmet_put_namespace(ns);
+}
+
+struct nvmet_ns *nvmet_ns_alloc(struct nvmet_subsys *subsys, u32 nsid)
+{
+	struct nvmet_ns *ns;
+
+	ns = kzalloc(sizeof(*ns), GFP_KERNEL);
+	if (!ns)
+		return NULL;
+
+	kref_init(&ns->ref);
+	ns->nsid = nsid;
+	ns->subsys = subsys;
+	return ns;
+}
+
+void nvmet_req_complete(struct nvmet_req *req, u16 status)
+{
+	if (status)
+		nvmet_set_status(req, status);
+
+	/* XXX: need to fill in something useful for sq_head */
+	req->rsp->sq_head = 0;
+	req->rsp->sq_id = cpu_to_le16(req->sq->qid);
+	req->rsp->command_id = req->cmd->common.command_id;
+
+	if (req->ns)
+		nvmet_put_namespace(req->ns);
+	req->queue_response(req);
+}
+EXPORT_SYMBOL_GPL(nvmet_req_complete);
+
+void nvmet_cq_init(struct nvmet_ctrl *ctrl, struct nvmet_cq *cq,
+		u16 qid, u16 size)
+{
+	cq->qid = qid;
+	cq->size = size;
+
+	ctrl->cqs[qid] = cq;
+}
+EXPORT_SYMBOL_GPL(nvmet_cq_init);
+
+void nvmet_sq_init(struct nvmet_ctrl *ctrl, struct nvmet_sq *sq,
+		u16 qid, u16 size)
+{
+	sq->ctrl = ctrl;
+	sq->qid = qid;
+	sq->size = size;
+
+	ctrl->sqs[qid] = sq;
+}
+EXPORT_SYMBOL_GPL(nvmet_sq_init);
+
+void nvmet_sq_destroy(struct nvmet_sq *sq)
+{
+	if (sq->ctrl)
+		nvmet_ctrl_put(sq->ctrl);
+}
+EXPORT_SYMBOL_GPL(nvmet_sq_destroy);
+
+u16 nvmet_req_init(struct nvmet_req *req, struct nvmet_cq *cq,
+		struct nvmet_sq *sq,
+		void (*queue_response)(struct nvmet_req *req))
+{
+	u16 status;
+
+	req->cq = cq;
+	req->sq = sq;
+	req->queue_response = queue_response;
+	req->sg = NULL;
+	req->sg_cnt = 0;
+	req->rsp->status = 0;
+
+	if (unlikely(req->sq->qid == 0))
+		status = nvmet_parse_admin_cmd(req);
+	else
+		status = nvmet_parse_io_cmd(req);
+
+	if (status)
+		return status;
+
+	if (unlikely(!req->sq->ctrl)) {
+		pr_err("queue not connected!\n");
+		return NVME_SC_QID_INVALID | NVME_SC_DNR;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nvmet_req_init);
+
+static inline bool nvmet_cc_en(u32 cc)
+{
+	return cc & 0x1;
+}
+
+static inline u8 nvmet_cc_css(u32 cc)
+{
+	return (cc >> 4) & 0x7;
+}
+
+static inline u8 nvmet_cc_mps(u32 cc)
+{
+	return (cc >> 7) & 0xf;
+}
+
+static inline u8 nvmet_cc_ams(u32 cc)
+{
+	return (cc >> 11) & 0x7;
+}
+
+static inline u8 nvmet_cc_shn(u32 cc)
+{
+	return (cc >> 14) & 0x3;
+}
+
+static inline u8 nvmet_cc_iosqes(u32 cc)
+{
+	return (cc >> 16) & 0xf;
+}
+
+static inline u8 nvmet_cc_iocqes(u32 cc)
+{
+	return (cc >> 20) & 0xf;
+}
+
+static void nvmet_start_ctrl(struct nvmet_ctrl *ctrl)
+{
+#if 0
+	    nvmet_cc_iosqes(n->bar.cc) < NVME_CTRL_SQES_MIN(n->id_ctrl.sqes) ||
+	    nvmet_cc_iosqes(n->bar.cc) > NVME_CTRL_SQES_MAX(n->id_ctrl.sqes) ||
+	    nvmet_cc_iocqes(n->bar.cc) < NVME_CTRL_CQES_MIN(n->id_ctrl.cqes) ||
+	    nvmet_cc_iocqes(n->bar.cc) > NVME_CTRL_CQES_MAX(n->id_ctrl.cqes) ||
+#endif
+	if (nvmet_cc_mps(ctrl->cc) != 0 ||
+	    nvmet_cc_ams(ctrl->cc) != 0 ||
+	    nvmet_cc_css(ctrl->cc) != 0) {
+		ctrl->csts = NVME_CSTS_CFS;
+		return;
+	}
+
+	ctrl->csts = NVME_CSTS_RDY;
+}
+
+static void nvmet_clear_ctrl(struct nvmet_ctrl *ctrl)
+{
+	/* XXX: tear down queues? */
+	ctrl->csts &= ~NVME_CSTS_RDY;
+	ctrl->cc = 0;
+}
+
+void nvmet_update_cc(struct nvmet_ctrl *ctrl, u32 new)
+{
+	u32 old;
+
+	/* XXX: locking? */
+	old = ctrl->cc;
+	ctrl->cc = new;
+
+	if (nvmet_cc_en(new) && !nvmet_cc_en(old))
+		nvmet_start_ctrl(ctrl);
+	if (!nvmet_cc_en(new) && nvmet_cc_en(old))
+		nvmet_clear_ctrl(ctrl);
+	if (nvmet_cc_shn(new) && !nvmet_cc_shn(old)) {
+		nvmet_clear_ctrl(ctrl);
+		ctrl->csts |= NVME_CSTS_SHST_CMPLT;
+	}
+	if (!nvmet_cc_shn(new) && nvmet_cc_shn(old))
+		ctrl->csts &= ~NVME_CSTS_SHST_CMPLT;
+}
+EXPORT_SYMBOL_GPL(nvmet_update_cc);
+
+struct nvmet_ctrl *nvmet_ctrl_find_get(struct nvmet_subsys *subsys, u16 cntlid)
+{
+	struct nvmet_ctrl *ctrl;
+
+	lockdep_assert_held(&subsys->lock);
+
+	list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
+		if (ctrl->cntlid == cntlid) {
+			if (kref_get_unless_zero(&ctrl->ref))
+				return ctrl;
+			return NULL;
+		}
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(nvmet_ctrl_find_get);
+
+struct nvmet_ctrl *nvmet_alloc_ctrl(struct nvmet_subsys *subsys,
+		const char *subsys_name)
+{
+	struct nvmet_ctrl *ctrl;
+	int ret = -ENOMEM;
+
+	lockdep_assert_held(&subsys->lock);
+
+	ctrl = kzalloc(sizeof(*ctrl), GFP_KERNEL);
+	if (!ctrl)
+		goto out;
+
+	/* command sets supported: NVMe command set: */
+	ctrl->cap |= (1ULL << 37);
+	/* CC.EN timeout in 500msec units: */
+	ctrl->cap |= (15ULL << 24);
+	/* maximum queue entries supported: */
+	ctrl->cap |= NVMET_QUEUE_SIZE - 1;
+
+	memcpy(ctrl->subsys_name, subsys_name, NVMET_SUBSYS_NAME_LEN);
+
+	kref_init(&ctrl->ref);
+	ctrl->subsys = subsys;
+
+	ctrl->cqs = kcalloc(subsys->max_qid + 1,
+			sizeof(struct nvmet_queue *),
+			GFP_KERNEL);
+	if (!ctrl->cqs)
+		goto out_free_ctrl;
+
+	ctrl->sqs = kcalloc(subsys->max_qid + 1,
+			sizeof(struct nvmet_queue *),
+			GFP_KERNEL);
+	if (!ctrl->sqs)
+		goto out_free_cqs;
+
+	ctrl->cntlid = ida_simple_get(&subsys->cntlid_ida, 0, USHRT_MAX - 1,
+			GFP_KERNEL);
+	if (ctrl->cntlid < 0) {
+		ret = ctrl->cntlid;
+		goto out_free_sqs;
+	}
+
+	list_add_tail(&ctrl->subsys_entry, &subsys->ctrls);
+	return ctrl;
+
+out_free_sqs:
+	kfree(ctrl->sqs);
+out_free_cqs:
+	kfree(ctrl->cqs);
+out_free_ctrl:
+	kfree(ctrl);
+out:
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(nvmet_alloc_ctrl);
+
+static void nvmet_ctrl_free(struct kref *ref)
+{
+	struct nvmet_ctrl *ctrl = container_of(ref, struct nvmet_ctrl, ref);
+	struct nvmet_subsys *subsys = ctrl->subsys;
+
+	mutex_lock(&ctrl->subsys->lock);
+	list_del(&ctrl->subsys_entry);
+	mutex_unlock(&ctrl->subsys->lock);
+
+	mutex_lock(&subsys->lock);
+	ida_simple_remove(&subsys->cntlid_ida, ctrl->cntlid);
+	mutex_unlock(&subsys->lock);
+
+	kfree(ctrl->sqs);
+	kfree(ctrl->cqs);
+	kfree(ctrl);
+}
+
+void nvmet_ctrl_put(struct nvmet_ctrl *ctrl)
+{
+	kref_put(&ctrl->ref, nvmet_ctrl_free);
+}
+
+struct nvmet_subsys *nvmet_find_subsys(char *subsys_name)
+{
+	struct nvmet_subsys *subsys;
+
+	mutex_lock(&nvmet_subsystem_mutex);
+	list_for_each_entry(subsys, &nvmet_subsystems, entry) {
+		if (!strncmp(subsys->subsys_name, subsys_name,
+				NVMET_SUBSYS_NAME_LEN)) {
+			/* XXX: need to start refcounting subsystems.. */
+			mutex_unlock(&nvmet_subsystem_mutex);
+			return subsys;
+		}
+	}
+	mutex_unlock(&nvmet_subsystem_mutex);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(nvmet_find_subsys);
+
+struct nvmet_subsys *nvmet_subsys_alloc(const char *subsys_name)
+{
+	struct nvmet_subsys *subsys;
+
+	subsys = kzalloc(sizeof(*subsys), GFP_KERNEL);
+	if (!subsys)
+		return NULL;
+
+	subsys->subsys_name = kstrndup(subsys_name, NVMET_SUBSYS_NAME_LEN,
+			GFP_KERNEL);
+	if (IS_ERR(subsys->subsys_name)) {
+		kfree(subsys);
+		return NULL;
+	}
+
+	mutex_init(&subsys->lock);
+	INIT_LIST_HEAD(&subsys->namespaces);
+	INIT_LIST_HEAD(&subsys->ctrls);
+
+	ida_init(&subsys->cntlid_ida);
+	subsys->max_qid = NVMET_NR_QUEUES;
+
+	mutex_lock(&nvmet_subsystem_mutex);
+	list_add_tail(&subsys->entry, &nvmet_subsystems);
+	mutex_unlock(&nvmet_subsystem_mutex);
+
+	return subsys;
+}
+
+void nvmet_subsys_free(struct nvmet_subsys *subsys)
+{
+	WARN_ON_ONCE(!list_empty(&subsys->namespaces));
+
+	mutex_lock(&nvmet_subsystem_mutex);
+	list_del(&subsys->entry);
+	mutex_unlock(&nvmet_subsystem_mutex);
+
+	kfree(subsys->subsys_name);
+	kfree(subsys);
+}
+
+static int __init nvmet_init(void)
+{
+	return nvmet_init_configfs();
+}
+
+static void __exit nvmet_exit(void)
+{
+	nvmet_exit_configfs();
+}
+
+module_init(nvmet_init);
+module_exit(nvmet_exit);
+
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/nvme/target/io-cmd.c b/drivers/nvme/target/io-cmd.c
new file mode 100644
index 0000000..2cf1811
--- /dev/null
+++ b/drivers/nvme/target/io-cmd.c
@@ -0,0 +1,114 @@
+/*
+ * Copyright (c) 2015 HGST, a Western Digital Company.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/blkdev.h>
+#include <linux/module.h>
+#include "nvmet.h"
+
+static void nvmet_bio_done(struct bio *bio)
+{
+	nvmet_req_complete(bio->bi_private,
+		bio->bi_error ? NVME_SC_INTERNAL | NVME_SC_DNR : 0);
+	bio_put(bio);
+}
+
+static void nvmet_execute_rw(struct nvmet_req *req)
+{
+	int sg_cnt = req->sg_cnt;
+	struct scatterlist *sg;
+	struct bio *bio;
+	sector_t sector;
+	int rw, i;
+
+	if (!req->sg_cnt) {
+		nvmet_req_complete(req, 0);
+		return;
+	}
+
+	if (req->cmd->rw.opcode == nvme_cmd_write) {
+		if (req->cmd->rw.control & cpu_to_le16(NVME_RW_FUA))
+			rw = WRITE_FUA;
+		else
+			rw = WRITE;
+	} else {
+		rw = READ;
+	}
+
+	sector = le64_to_cpu(req->cmd->rw.slba);
+	sector <<= (req->ns->blksize_shift - 9);
+
+	bio = bio_alloc(GFP_KERNEL, min(sg_cnt, BIO_MAX_PAGES));
+	bio->bi_bdev = req->ns->bdev;
+	bio->bi_iter.bi_sector = sector;
+	bio->bi_private = req;
+	bio->bi_end_io = nvmet_bio_done;
+
+	for_each_sg(req->sg, sg, req->sg_cnt, i) {
+		if (bio_add_page(bio, sg_page(sg), sg->length, sg->offset)
+				!= sg->length) {
+			struct bio *prev = bio;
+
+			bio = bio_alloc(GFP_KERNEL, min(sg_cnt, BIO_MAX_PAGES));
+			bio->bi_bdev = req->ns->bdev;
+			bio->bi_iter.bi_sector = sector;
+
+			bio_chain(bio, prev);
+			submit_bio(rw, prev);
+		}
+
+		sector += sg->length >> 9;
+		sg_cnt--;
+	}
+
+	submit_bio(rw, bio);
+}
+
+static void nvmet_execute_flush(struct nvmet_req *req)
+{
+	struct bio *bio = bio_alloc(GFP_KERNEL, 0);
+
+	bio->bi_bdev = req->ns->bdev;
+	bio->bi_private = req;
+	bio->bi_end_io = nvmet_bio_done;
+
+	submit_bio(WRITE_FLUSH, bio);
+}
+
+int nvmet_parse_io_cmd(struct nvmet_req *req)
+{
+	struct nvme_command *cmd = req->cmd;
+
+	req->ns = nvmet_find_namespace(req->sq->ctrl, cmd->rw.nsid);
+	if (!req->ns)
+		return NVME_SC_INVALID_NS | NVME_SC_DNR;
+
+	switch (cmd->common.opcode) {
+	case nvme_cmd_read:
+		req->execute = nvmet_execute_rw;
+		req->data_len = ((u32)le16_to_cpu(cmd->rw.length) + 1) <<
+				req->ns->blksize_shift;
+		return 0;
+	case nvme_cmd_write:
+		req->execute = nvmet_execute_rw;
+		req->data_len = ((u32)le16_to_cpu(cmd->rw.length) + 1) <<
+				req->ns->blksize_shift;
+		return 0;
+	case nvme_cmd_flush:
+		req->execute = nvmet_execute_flush;
+		req->data_len = 0;
+		return 0;
+	default:
+		pr_err("nvmet: unhandled cmd %d\n", cmd->common.opcode);
+		return NVME_SC_INVALID_OPCODE | NVME_SC_DNR;
+	}
+}
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
new file mode 100644
index 0000000..9335584
--- /dev/null
+++ b/drivers/nvme/target/nvmet.h
@@ -0,0 +1,172 @@
+#ifndef _NVME_CMD_H
+#define _NVME_CMD_H
+
+#include <linux/dma-mapping.h>
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/kref.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/nvme.h>
+#include <linux/configfs.h>
+#include <linux/rcupdate.h>
+
+struct nvmet_ns {
+	struct list_head	dev_link;
+	struct kref		ref;
+	struct block_device	*bdev;
+	u32			nsid;
+	u32			blksize_shift;
+	loff_t			size;
+
+	struct nvmet_subsys	*subsys;
+	const char		*device_path;
+
+	struct config_group	device_group;
+	struct config_group	default_groups[2];
+	struct config_group	group;
+	struct rcu_head		rcu;
+};
+
+static inline struct nvmet_ns *to_nvmet_ns(struct config_item *item)
+{
+	return container_of(to_config_group(item), struct nvmet_ns, group);
+}
+
+struct nvmet_cq {
+	u16			qid;
+	u16			size;
+};
+
+struct nvmet_sq {
+	struct nvmet_ctrl	*ctrl;
+	u16			qid;
+	u16			size;
+};
+
+struct nvmet_ctrl {
+	struct nvmet_subsys	*subsys;
+	struct nvmet_cq		**cqs;
+	struct nvmet_sq		**sqs;
+
+	u64			cap;
+	u32			cc;
+	u32			csts;
+
+	u16			cntlid;
+
+	struct list_head	subsys_entry;
+	struct kref		ref;
+#define NVMET_SUBSYS_NAME_LEN		256
+	char			subsys_name[NVMET_SUBSYS_NAME_LEN];
+};
+
+struct nvmet_subsys {
+	struct mutex		lock;
+
+	struct list_head	namespaces;
+	unsigned int		max_nsid;
+
+	struct list_head	ctrls;
+	struct ida		cntlid_ida;
+
+	u16			max_qid;
+
+	u64			ver;
+	char			*subsys_name;
+
+	struct list_head	entry;
+	struct config_group	group;
+
+	struct config_group	namespaces_group;
+	struct config_group	controllers_group;
+	struct config_group	*default_groups[3];
+};
+
+static inline struct nvmet_subsys *to_subsys(struct config_item *item)
+{
+	return container_of(to_config_group(item), struct nvmet_subsys, group);
+}
+
+static inline struct nvmet_subsys *namespaces_to_subsys(
+		struct config_item *item)
+{
+	return container_of(to_config_group(item), struct nvmet_subsys,
+			namespaces_group);
+}
+
+struct nvmet_req {
+	struct nvme_command	*cmd;
+	struct nvme_completion	*rsp;
+	struct nvmet_sq		*sq;
+	struct nvmet_cq		*cq;
+	struct nvmet_ns		*ns;
+	struct scatterlist	*sg;
+	int			sg_cnt;
+	size_t			data_len;
+
+	void (*execute)(struct nvmet_req *req);
+	void (*queue_response)(struct nvmet_req *req);
+};
+
+static inline void nvmet_set_status(struct nvmet_req *req, u16 status)
+{
+	req->rsp->status = cpu_to_le16(status << 1);
+}
+
+static inline void nvmet_set_result(struct nvmet_req *req, u32 result)
+{
+	req->rsp->result = cpu_to_le32(result);
+}
+
+static inline bool nvmet_is_write(struct nvmet_req *req)
+{
+	return req->cmd->common.opcode & 1;
+}
+
+/*
+ * NVMe command writes actually are DMA reads for us on the target side.
+ */
+static inline enum dma_data_direction
+nvmet_data_dir(struct nvmet_req *cmd)
+{
+	return nvmet_is_write(cmd) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+}
+
+int nvmet_parse_io_cmd(struct nvmet_req *req);
+int nvmet_parse_admin_cmd(struct nvmet_req *req);
+
+u16 nvmet_req_init(struct nvmet_req *req, struct nvmet_cq *cq,
+		struct nvmet_sq *sq,
+		void (*queue_response)(struct nvmet_req *req));
+void nvmet_req_complete(struct nvmet_req *req, u16 status);
+
+void nvmet_cq_init(struct nvmet_ctrl *ctrl, struct nvmet_cq *cq, u16 qid,
+		u16 size);
+void nvmet_sq_init(struct nvmet_ctrl *ctrl, struct nvmet_sq *sq, u16 qid,
+		u16 size);
+void nvmet_sq_destroy(struct nvmet_sq *sq);
+
+void nvmet_update_cc(struct nvmet_ctrl *ctrl, u32 new);
+struct nvmet_ctrl *nvmet_alloc_ctrl(struct nvmet_subsys *subsys,
+		const char *subsys_name);
+struct nvmet_ctrl *nvmet_ctrl_find_get(struct nvmet_subsys *subsys, u16 cntlid);
+void nvmet_ctrl_put(struct nvmet_ctrl *ctrl);
+
+struct nvmet_subsys *nvmet_find_subsys(char *subsys_name);
+struct nvmet_subsys *nvmet_subsys_alloc(const char *subsys_name);
+void nvmet_subsys_free(struct nvmet_subsys *subsys);
+
+struct nvmet_ns *nvmet_find_namespace(struct nvmet_ctrl *ctrl, __le32 nsid);
+void nvmet_put_namespace(struct nvmet_ns *ns);
+int nvmet_ns_enable(struct nvmet_ns *ns, const char *path);
+struct nvmet_ns *nvmet_ns_alloc(struct nvmet_subsys *subsys, u32 nsid);
+void nvmet_ns_free(struct nvmet_ns *ns);
+
+#define NVMET_QUEUE_SIZE	1024
+#define NVMET_NR_QUEUES		64
+
+int __init nvmet_init_configfs(void);
+void __exit nvmet_exit_configfs(void);
+
+#endif /* _NVME_CMD_H */
-- 
1.9.1

[PATCH 7/8] nvmet: add a generic NVMe target

[Sagi Grimberg]

> +void nvmet_ns_free(struct nvmet_ns *ns)
> +{
> +	struct nvmet_subsys *subsys = ns->subsys;
> +
> +	mutex_lock(&subsys->lock);
> +	if (!list_empty(&ns->dev_link))
> +		list_del_init(&ns->dev_link);
> +	mutex_unlock(&subsys->lock);
> +
> +	nvmet_put_namespace(ns);
> +}
> +
> +struct nvmet_ns *nvmet_ns_alloc(struct nvmet_subsys *subsys, u32 nsid)
> +{
> +	struct nvmet_ns *ns;
> +
> +	ns = kzalloc(sizeof(*ns), GFP_KERNEL);
> +	if (!ns)
> +		return NULL;
> +

This lacks also:
INIT_LIST_HEAD(&ns->dev_link);

So the list_empty() check in ns_free won't be bogus...
It causes a NULL deref on configfs rmdir.

> +	kref_init(&ns->ref);
> +	ns->nsid = nsid;
> +	ns->subsys = subsys;
> +	return ns;
> +}

[PATCH 7/8] nvmet: add a generic NVMe target

[Christoph Hellwig]

Agreed, I'll fix it up.

[PATCH 8/8] nvme-loop: add a NVMe loopback device

[Christoph Hellwig]

Usage:

------ snip ------
NAME="testsubsystem"
DEV="/dev/?da"

mkdir /sys/kernel/config/nvmet/subsystems/${NAME}
mkdir /sys/kernel/config/nvmet/subsystems/${NAME}/namespaces/1
echo -n ${DEV} > /sys/kernel/config/nvmet/subsystems/${NAME}/namespaces/1/device_path

echo "name=${NAME}" > /sys/class/nvme-loop/ctl/add_ctrl
------ snip ------

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 drivers/nvme/target/Kconfig  |  10 +
 drivers/nvme/target/Makefile |   2 +
 drivers/nvme/target/loop.c   | 688 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 700 insertions(+)
 create mode 100644 drivers/nvme/target/loop.c

diff --git a/drivers/nvme/target/Kconfig b/drivers/nvme/target/Kconfig
index 9a3d742..1bf92db 100644
--- a/drivers/nvme/target/Kconfig
+++ b/drivers/nvme/target/Kconfig
@@ -2,3 +2,13 @@
 config NVME_TARGET
 	depends on BLOCK
 	tristate
+
+config NVME_TARGET_LOOP
+	tristate "NVMe loopback device support"
+	depends on BLK_DEV_NVME
+	select NVME_TARGET
+	help
+	  This enabled the NVMe loopback device support, which can be useful
+	  to test NVMe host and target side features.
+
+	  If unsure, say N.
diff --git a/drivers/nvme/target/Makefile b/drivers/nvme/target/Makefile
index 9c236e4..21e9134 100644
--- a/drivers/nvme/target/Makefile
+++ b/drivers/nvme/target/Makefile
@@ -1,4 +1,6 @@
 
 obj-$(CONFIG_NVME_TARGET)		+= nvmet.o
+obj-$(CONFIG_NVME_TARGET_LOOP)		+= nvme-loop.o
 
 nvmet-y		+= core.o configfs.o admin-cmd.o io-cmd.o
+nvme-loop-y	+= loop.o
diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c
new file mode 100644
index 0000000..446bdff
--- /dev/null
+++ b/drivers/nvme/target/loop.c
@@ -0,0 +1,688 @@
+/*
+ * Copyright (c) 2015 HGST, a Western Digital Company.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/scatterlist.h>
+#include <linux/delay.h>
+#include <linux/blk-mq.h>
+#include <linux/nvme.h>
+#include <linux/module.h>
+#include <linux/parser.h>
+#include <linux/t10-pi.h>
+#include "nvmet.h"
+#include "../host/nvme.h"
+
+#define NVME_LOOP_MAX_Q_DEPTH		1024
+#define NVME_LOOP_AQ_DEPTH		256
+
+#define NVME_LOOP_MAX_SEGMENTS		32
+
+struct nvme_loop_ctrl {
+	spinlock_t		lock;
+	struct nvme_loop_queue	*queues;
+	u32			queue_count;
+	size_t			queue_size;
+
+	struct blk_mq_tag_set	admin_tag_set;
+
+	u16			cntlid;
+	char			*subsys_name;
+
+	struct list_head	list;
+	u64			cap;
+	struct blk_mq_tag_set	tag_set;
+	struct nvme_ctrl	ctrl;
+
+	struct nvmet_ctrl	*target_ctrl;
+};
+
+static inline struct nvme_loop_ctrl *to_loop_ctrl(struct nvme_ctrl *ctrl)
+{
+	return container_of(ctrl, struct nvme_loop_ctrl, ctrl);
+}
+
+struct nvme_loop_queue {
+	struct nvmet_cq		nvme_cq;
+	struct nvmet_sq		nvme_sq;
+	struct nvme_loop_ctrl	*ctrl;
+};
+
+struct nvme_loop_iod {
+	struct scatterlist	sg[NVME_LOOP_MAX_SEGMENTS];
+	struct nvme_command	cmd;
+	struct nvme_completion	rsp;
+	struct nvmet_req	req;
+	struct work_struct	work;
+};
+
+static int nr_io_queues;
+module_param(nr_io_queues, int, 0444);
+MODULE_PARM_DESC(nr_io_queues,
+	 "Number of I/O queues.  Default is one per CPU");
+
+static LIST_HEAD(nvme_loop_ctrl_list);
+static DEFINE_MUTEX(nvme_loop_ctrl_mutex);
+
+static inline int nvme_loop_queue_idx(struct nvme_loop_queue *queue)
+{
+	return queue - queue->ctrl->queues;
+}
+
+static void nvme_loop_complete_rq(struct request *req)
+{
+	int error = 0;
+
+	if (unlikely(req->errors)) {
+		if (nvme_req_needs_retry(req, req->errors)) {
+			nvme_requeue_req(req);
+			return;
+		}
+
+		if (req->cmd_type == REQ_TYPE_DRV_PRIV)
+			error = req->errors;
+		else
+			error = nvme_error_status(req->errors);
+	}
+
+	blk_mq_end_request(req, error);
+}
+
+static void nvme_loop_queue_response(struct nvmet_req *nvme_req)
+{
+	struct nvme_loop_iod *iod =
+		container_of(nvme_req, struct nvme_loop_iod, req);
+	struct nvme_completion *cqe = &iod->rsp;
+	struct request *req = blk_mq_rq_from_pdu(iod);
+
+	if (req->cmd_type == REQ_TYPE_DRV_PRIV)
+		req->special = (void *)(uintptr_t)le32_to_cpu(cqe->result);
+	blk_mq_complete_request(req, le16_to_cpu(cqe->status) >> 1);
+}
+
+static void nvme_loop_execute_work(struct work_struct *work)
+{
+	struct nvme_loop_iod *iod =
+		container_of(work, struct nvme_loop_iod, work);
+
+	iod->req.execute(&iod->req);
+}
+
+static int nvme_loop_queue_rq(struct blk_mq_hw_ctx *hctx,
+		const struct blk_mq_queue_data *bd)
+{
+	struct nvme_ns *ns = hctx->queue->queuedata;
+	struct nvme_loop_queue *queue = hctx->driver_data;
+	struct request *req = bd->rq;
+	struct nvme_loop_iod *iod = blk_mq_rq_to_pdu(req);
+	int ret;
+
+	switch (req->cmd_type) {
+	case REQ_TYPE_FS:
+		if (req->cmd_flags & REQ_FLUSH)
+			nvme_setup_flush(ns, &iod->cmd);
+		else
+			nvme_setup_rw(ns, req, &iod->cmd);
+		break;
+	case REQ_TYPE_DRV_PRIV:
+		memcpy(&iod->cmd, req->cmd, sizeof(struct nvme_command));
+		break;
+	default:
+		return BLK_MQ_RQ_QUEUE_ERROR;
+	}
+
+	ret = nvmet_req_init(&iod->req, &queue->nvme_cq, &queue->nvme_sq,
+			nvme_loop_queue_response);
+	if (ret)
+		goto out_err;
+
+	if (blk_rq_bytes(req)) {
+		sg_init_table(iod->sg, req->nr_phys_segments);
+
+		iod->req.sg = iod->sg;
+		iod->req.sg_cnt = blk_rq_map_sg(req->q, req, iod->sg);
+		BUG_ON(iod->req.sg_cnt > req->nr_phys_segments);
+	}
+
+	iod->cmd.common.command_id = req->tag;
+	blk_mq_start_request(req);
+
+	schedule_work(&iod->work);
+	return 0;
+out_err:
+	return BLK_MQ_RQ_QUEUE_ERROR;
+}
+
+static int __nvme_loop_init_request(struct nvme_loop_ctrl *ctrl,
+		struct request *req, unsigned int queue_idx)
+{
+	struct nvme_loop_iod *iod = blk_mq_rq_to_pdu(req);
+
+	BUG_ON(queue_idx >= ctrl->queue_count);
+
+	iod->req.cmd = &iod->cmd;
+	iod->req.rsp = &iod->rsp;
+	INIT_WORK(&iod->work, nvme_loop_execute_work);
+	return 0;
+}
+
+static int nvme_loop_init_request(void *data, struct request *req,
+				unsigned int hctx_idx, unsigned int rq_idx,
+				unsigned int numa_node)
+{
+	return __nvme_loop_init_request(data, req, hctx_idx + 1);
+}
+
+static int nvme_loop_init_admin_request(void *data, struct request *req,
+				unsigned int hctx_idx, unsigned int rq_idx,
+				unsigned int numa_node)
+{
+	return __nvme_loop_init_request(data, req, 0);
+}
+
+static int nvme_loop_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
+		unsigned int hctx_idx)
+{
+	struct nvme_loop_ctrl *ctrl = data;
+	struct nvme_loop_queue *queue = &ctrl->queues[hctx_idx + 1];
+
+	BUG_ON(hctx_idx >= ctrl->queue_count);
+
+	hctx->driver_data = queue;
+	return 0;
+}
+
+static int nvme_loop_init_admin_hctx(struct blk_mq_hw_ctx *hctx, void *data,
+		unsigned int hctx_idx)
+{
+	struct nvme_loop_ctrl *ctrl = data;
+	struct nvme_loop_queue *queue = &ctrl->queues[0];
+
+	BUG_ON(hctx_idx != 0);
+
+	hctx->driver_data = queue;
+	return 0;
+}
+
+static struct blk_mq_ops nvme_loop_mq_ops = {
+	.queue_rq	= nvme_loop_queue_rq,
+	.complete	= nvme_loop_complete_rq,
+	.map_queue	= blk_mq_map_queue,
+	.init_request	= nvme_loop_init_request,
+	.init_hctx	= nvme_loop_init_hctx,
+};
+
+static struct blk_mq_ops nvme_loop_admin_mq_ops = {
+	.queue_rq	= nvme_loop_queue_rq,
+	.complete	= nvme_loop_complete_rq,
+	.map_queue	= blk_mq_map_queue,
+	.init_request	= nvme_loop_init_admin_request,
+	.init_hctx	= nvme_loop_init_admin_hctx,
+};
+
+static void nvme_loop_destroy_admin_queue(struct nvme_loop_ctrl *ctrl)
+{
+	blk_cleanup_queue(ctrl->ctrl.admin_q);
+	blk_mq_free_tag_set(&ctrl->admin_tag_set);
+	nvme_shutdown_ctrl(&ctrl->ctrl);
+	/* disconnect queue */
+}
+
+static void nvme_loop_free_ctrl(struct nvme_ctrl *nctrl)
+{
+	struct nvme_loop_ctrl *ctrl = to_loop_ctrl(nctrl);
+
+	list_del(&ctrl->list);
+#if 0
+	for (i = 1; i < ctrl->queue_count; i++)
+		/* disconnect queue */
+#endif
+	blk_mq_free_tag_set(&ctrl->tag_set);
+	nvme_loop_destroy_admin_queue(ctrl);
+	kfree(ctrl->queues);
+	kfree(ctrl->subsys_name);
+	kfree(ctrl);
+}
+
+static int nvme_loop_init_queue(struct nvme_loop_ctrl *ctrl, int idx,
+		size_t queue_size)
+{
+	struct nvme_loop_queue *queue;
+	struct nvmet_subsys *subsys;
+	struct nvmet_ctrl *target_ctrl = NULL;
+	u16 qid, cntlid;
+	int ret = 0;
+
+	queue = &ctrl->queues[idx];
+	queue->ctrl = ctrl;
+	
+	qid = nvme_loop_queue_idx(queue);
+	cntlid = qid ? ctrl->cntlid : 0xffff;
+
+	subsys = nvmet_find_subsys(ctrl->subsys_name);
+	if (!subsys) {
+		pr_warn("connect request for invalid subsystem!\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&subsys->lock);
+	target_ctrl = nvmet_ctrl_find_get(subsys, cntlid);
+	if (target_ctrl) {
+		pr_info("adding queue %d to ctrl %d.\n",
+			qid, target_ctrl->cntlid);
+	} else {
+		BUG_ON(qid != 0);
+
+		target_ctrl = nvmet_alloc_ctrl(subsys, ctrl->subsys_name);
+		if (IS_ERR(target_ctrl)) {
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+
+		pr_info("creating controller %d.\n", target_ctrl->cntlid);
+	}
+
+	nvmet_cq_init(target_ctrl, &queue->nvme_cq, qid,
+			qid ? ctrl->queue_size : NVME_LOOP_AQ_DEPTH);
+	nvmet_sq_init(target_ctrl, &queue->nvme_sq, qid,
+			qid ? ctrl->queue_size : NVME_LOOP_AQ_DEPTH);
+	if (!qid)
+		ctrl->cntlid = target_ctrl->cntlid;
+
+	if (!ctrl->target_ctrl)
+		ctrl->target_ctrl = target_ctrl;
+
+out_unlock:
+	mutex_unlock(&subsys->lock);
+	return ret;
+}
+
+static int nvme_loop_configure_admin_queue(struct nvme_loop_ctrl *ctrl)
+{
+	unsigned page_shift = PAGE_SHIFT;
+	unsigned dev_page_min, dev_page_max;
+	int error;
+
+	error = nvme_loop_init_queue(ctrl, 0, NVME_LOOP_AQ_DEPTH);
+	if (error) {
+		dev_err(ctrl->ctrl.dev,
+			"failed to initialize admin queue: %d\n", error);
+		return error;
+	}
+
+	error = ctrl->ctrl.ops->reg_read64(&ctrl->ctrl, NVME_REG_CAP,
+			&ctrl->cap);
+	if (error) {
+		dev_err(ctrl->ctrl.dev,
+			"prop_get NVME_REG_CAP failed\n");
+		return error;
+	}
+
+	dev_page_min = NVME_CAP_MPSMIN(ctrl->cap) + 12;
+	if (page_shift < dev_page_min) {
+		dev_err(ctrl->ctrl.dev,
+			"Minimum device page size (%u) too large for "
+			"host (%u)\n", 1 << dev_page_min, 1 << page_shift);
+		return -ENODEV;
+	}
+
+	dev_page_max = NVME_CAP_MPSMAX(ctrl->cap) + 12;
+	if (page_shift > dev_page_max) {
+		dev_info(ctrl->ctrl.dev,
+			"Device maximum page size (%u) smaller than "
+			"host (%u); enabling work-around\n",
+			1 << dev_page_max, 1 << page_shift);
+		page_shift = dev_page_max;
+	}
+
+	ctrl->queue_size =
+		min_t(int, NVME_CAP_MQES(ctrl->cap) + 1, NVME_LOOP_MAX_Q_DEPTH);
+
+	error = nvme_enable_ctrl(&ctrl->ctrl, ctrl->cap, page_shift);
+	if (error)
+		return error;
+
+	memset(&ctrl->admin_tag_set, 0, sizeof(ctrl->admin_tag_set));
+	ctrl->admin_tag_set.ops = &nvme_loop_admin_mq_ops;
+	ctrl->admin_tag_set.queue_depth = NVME_LOOP_AQ_DEPTH;
+	ctrl->admin_tag_set.numa_node = NUMA_NO_NODE;
+	ctrl->admin_tag_set.cmd_size = sizeof(struct nvme_loop_iod);
+	ctrl->admin_tag_set.driver_data = ctrl;
+	ctrl->admin_tag_set.nr_hw_queues = 1;
+	ctrl->admin_tag_set.timeout = ADMIN_TIMEOUT;
+
+	error = blk_mq_alloc_tag_set(&ctrl->admin_tag_set);
+	if (error)
+		goto out_disable;
+
+	ctrl->ctrl.admin_q = blk_mq_init_queue(&ctrl->admin_tag_set);
+	if (IS_ERR(ctrl->ctrl.admin_q)) {
+		error = PTR_ERR(ctrl->ctrl.admin_q);
+		goto out_free_tagset;
+	}
+	ctrl->ctrl.admin_q->queuedata = ctrl;
+
+	return 0;
+
+out_free_tagset:
+	blk_mq_free_tag_set(&ctrl->admin_tag_set);
+out_disable:
+	nvme_shutdown_ctrl(&ctrl->ctrl);
+	return error;
+}
+
+static int nvme_loop_reg_read32(struct nvme_ctrl *ctrl, u32 off, u32 *val)
+{
+	struct nvmet_ctrl *target_ctrl = to_loop_ctrl(ctrl)->target_ctrl;
+
+	switch (off) {
+	case NVME_REG_VS:
+		*val = target_ctrl->subsys->ver;
+		return 0;
+	case NVME_REG_CSTS:
+		*val = target_ctrl->csts;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int nvme_loop_reg_read64(struct nvme_ctrl *ctrl, u32 off, u64 *val)
+{
+	struct nvmet_ctrl *target_ctrl = to_loop_ctrl(ctrl)->target_ctrl;
+
+	switch (off) {
+	case NVME_REG_CAP:
+		*val = target_ctrl->cap;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int nvme_loop_reg_write32(struct nvme_ctrl *ctrl, u32 off, u32 val)
+{
+	struct nvmet_ctrl *target_ctrl = to_loop_ctrl(ctrl)->target_ctrl;
+
+	switch (off) {
+	case NVME_REG_CC:
+		nvmet_update_cc(target_ctrl, val);
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static bool nvme_loop_io_incapable(struct nvme_ctrl *ctrl)
+{
+	/* XXX: */
+	return false;
+}
+
+static int nvme_loop_reset_ctrl(struct nvme_ctrl *ctrl)
+{
+	return -EIO;
+}
+
+static const struct nvme_ctrl_ops nvme_loop_ctrl_ops = {
+	.reg_read32		= nvme_loop_reg_read32,
+	.reg_read64		= nvme_loop_reg_read64,
+	.reg_write32		= nvme_loop_reg_write32,
+	.io_incapable		= nvme_loop_io_incapable,
+	.reset_ctrl		= nvme_loop_reset_ctrl,
+	.free_ctrl		= nvme_loop_free_ctrl,
+};
+
+enum {
+	NVME_OPT_ERR		= 0,
+	NVME_OPT_NAME		= 1 << 2,
+	NVME_OPT_REQUIRED	=
+	NVME_OPT_NAME,
+};
+
+static const match_table_t opt_tokens = {
+	{ NVME_OPT_NAME,	"name=%s"	},
+	{ NVME_OPT_ERR,		NULL		}
+};
+
+static int nvme_loop_parse_options(const char *buf, struct nvme_loop_ctrl *ctrl)
+{
+	substring_t args[MAX_OPT_ARGS];
+	char *options, *p, *o;
+	int token, ret = 0;
+	unsigned opt_mask = 0;
+
+	o = options = kstrdup(buf, GFP_KERNEL);
+	if (!options)
+		return -ENOMEM;
+
+	while ((p = strsep(&options, ",\n")) != NULL) {
+		if (!*p)
+			continue;
+
+		token = match_token(p, opt_tokens, args);
+		opt_mask |= token;
+		switch (token) {
+		case NVME_OPT_NAME:
+			p = match_strdup(args);
+			if (!p) {
+				ret = -ENOMEM;
+				goto out;
+			}
+			ctrl->subsys_name = p;
+			break;
+		default:
+			pr_warn("unknown parameter or missing value '%s' in ctrl creation request\n",
+				p);
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+	if ((opt_mask & NVME_OPT_REQUIRED) != NVME_OPT_REQUIRED) {
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(opt_tokens); i++) {
+			if ((opt_tokens[i].token & NVME_OPT_REQUIRED) &&
+			    !(opt_tokens[i].token & opt_mask)) {
+				pr_warn("nvmf: missing parameter '%s'\n",
+					opt_tokens[i].pattern);
+			}
+		}
+
+		ret = -EINVAL;
+	}
+
+out:
+	kfree(o);
+	return ret;
+}
+
+static ssize_t
+nvme_loop_create_ctrl(struct device *sysfs_dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct nvme_loop_ctrl *ctrl;
+	int ret, i;
+
+	ctrl = kzalloc(sizeof(*ctrl), GFP_KERNEL);
+	if (!ctrl)
+		return -ENOMEM;
+
+	ret = nvme_init_ctrl(&ctrl->ctrl, sysfs_dev, &nvme_loop_ctrl_ops,
+				0 /* no vendor.. */,
+				0 /* no quirks, we're perfect! */);
+	if (ret)
+		goto out_free_ctrl;
+
+	ret = nvme_loop_parse_options(buf, ctrl);
+	if (ret)
+		goto out_uninit_ctrl;
+
+	spin_lock_init(&ctrl->lock);
+
+	ret = -ENOMEM;
+	ctrl->queue_count = 1; /* admin queue */;
+	if (nr_io_queues > 0)
+		ctrl->queue_count += nr_io_queues;
+	else
+		ctrl->queue_count += num_possible_cpus();
+
+	ctrl->queues = kcalloc(ctrl->queue_count,
+			sizeof(*ctrl->queues), GFP_KERNEL);
+	if (!ctrl->queues)
+		goto out_uninit_ctrl;
+
+	ret = nvme_loop_configure_admin_queue(ctrl);
+	if (ret)
+		goto out_kfree_queues;
+
+	ret = nvme_set_queue_count(&ctrl->ctrl, ctrl->queue_count - 1);
+	if (ret <= 0) {
+		dev_err(ctrl->ctrl.dev,
+			"set_queue_count failed: %d\n", ret);
+		goto out_remove_admin_queue;
+	}
+
+	if (ret <= ctrl->queue_count)
+		ctrl->queue_count = ret + 1;
+
+	dev_info(ctrl->ctrl.dev,
+		"creating %d I/O queues.\n", ctrl->queue_count - 1);
+
+	for (i = 1; i < ctrl->queue_count; i++) {
+		ret = nvme_loop_init_queue(ctrl, i, ctrl->queue_size);
+		if (ret) {
+			dev_err(ctrl->ctrl.dev,
+				"failed to initialize I/O queue: %d\n", ret);
+			goto out_remove_admin_queue;
+		}
+	}
+
+	memset(&ctrl->tag_set, 0, sizeof(ctrl->tag_set));
+	ctrl->tag_set.ops = &nvme_loop_mq_ops;
+	ctrl->tag_set.queue_depth = ctrl->queue_size;
+	ctrl->tag_set.numa_node = NUMA_NO_NODE;
+	ctrl->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+	ctrl->tag_set.cmd_size = sizeof(struct nvme_loop_iod);
+	ctrl->tag_set.driver_data = ctrl;
+	ctrl->tag_set.nr_hw_queues = ctrl->queue_count - 1;
+	ctrl->tag_set.timeout = NVME_IO_TIMEOUT;
+	ctrl->ctrl.tagset = &ctrl->tag_set;
+
+	ret = blk_mq_alloc_tag_set(&ctrl->tag_set);
+	if (ret)
+		goto out_free_tag_set;
+
+	ret = nvme_init_identify(&ctrl->ctrl);
+	if (ret)
+		goto out_free_queues;
+
+	ctrl->ctrl.max_segments = NVME_LOOP_MAX_SEGMENTS;
+
+	nvme_scan_namespaces(&ctrl->ctrl);
+
+	pr_info("new ctrl: \"%s\"\n", ctrl->subsys_name);
+
+	mutex_lock(&nvme_loop_ctrl_mutex);
+	list_add_tail(&ctrl->list, &nvme_loop_ctrl_list);
+	mutex_unlock(&nvme_loop_ctrl_mutex);
+	return count;
+
+out_free_tag_set:
+	blk_mq_free_tag_set(&ctrl->tag_set);
+out_free_queues:
+#if 0
+	for (i = 1; i < ctrl->queue_count; i++)
+		/* disconnect queue */
+#endif
+out_remove_admin_queue:
+	nvme_loop_destroy_admin_queue(ctrl);
+out_kfree_queues:
+	kfree(ctrl->queues);
+out_uninit_ctrl:
+	nvme_uninit_ctrl(&ctrl->ctrl);
+out_free_ctrl:
+	kfree(ctrl);
+	return ret;
+}
+
+static DEVICE_ATTR(add_ctrl, S_IWUSR, NULL, nvme_loop_create_ctrl);
+
+static void __nvme_loop_remove_ctrl(struct nvme_loop_ctrl *ctrl)
+{
+	nvme_remove_namespaces(&ctrl->ctrl);
+	nvme_uninit_ctrl(&ctrl->ctrl);
+	nvme_put_ctrl(&ctrl->ctrl);
+}
+
+static struct class *nvme_loop_class;
+static struct device *nvme_loop_device;
+
+static int __init nvme_loop_init_module(void)
+{
+	int ret = -ENOMEM;
+
+	nvme_loop_class = class_create(THIS_MODULE, "nvme-loop");
+	if (IS_ERR(nvme_loop_class)) {
+		pr_err("couldn't register class nvme-loop\n");
+		ret = PTR_ERR(nvme_loop_class);
+		goto out;
+	}
+
+	nvme_loop_device =
+		device_create(nvme_loop_class, NULL, MKDEV(0, 0), NULL, "ctl");
+	if (IS_ERR(nvme_loop_device)) {
+		pr_err("couldn't create nvme-loop device!\n");
+		ret = PTR_ERR(nvme_loop_device);
+		goto out_destroy_class;
+	}
+
+	ret = device_create_file(nvme_loop_device, &dev_attr_add_ctrl);
+	if (ret) {
+		pr_err("couldn't add device attr.\n");
+		goto out_destroy_device;
+	}
+
+	return 0;
+
+out_destroy_device:
+	device_destroy(nvme_loop_class, MKDEV(0, 0));
+out_destroy_class:
+	class_destroy(nvme_loop_class);
+out:
+	return ret;
+}
+
+static void __exit nvme_loop_cleanup_module(void)
+{
+	struct nvme_loop_ctrl *ctrl;
+
+	mutex_lock(&nvme_loop_ctrl_mutex);
+	while (!list_empty(&nvme_loop_ctrl_list)) {
+		ctrl = list_entry(nvme_loop_ctrl_list.next,
+				struct nvme_loop_ctrl, list);
+
+		if (!list_empty(&ctrl->list))
+			list_del(&ctrl->list);
+
+		__nvme_loop_remove_ctrl(ctrl);
+	}
+	mutex_unlock(&nvme_loop_ctrl_mutex);
+
+	device_destroy(nvme_loop_class, MKDEV(0, 0));
+	class_destroy(nvme_loop_class);
+}
+
+module_init(nvme_loop_init_module);
+module_exit(nvme_loop_cleanup_module);
+
+MODULE_LICENSE("GPL v2");
-- 
1.9.1

[PATCH 8/8] nvme-loop: add a NVMe loopback device

[Sagi Grimberg]

> +static void nvme_loop_free_ctrl(struct nvme_ctrl *nctrl)
> +{
> +	struct nvme_loop_ctrl *ctrl = to_loop_ctrl(nctrl);
> +
> +	list_del(&ctrl->list);

This should be list_del_init so that cleanup_module
list_empty() check will be correct. unloading nvme-loop
with active controllers is getting a list corruption.

[PATCH 8/8] nvme-loop: add a NVMe loopback device

[Sagi Grimberg]

On 08/11/2015 12:54, Sagi Grimberg wrote:
>
>> +static void nvme_loop_free_ctrl(struct nvme_ctrl *nctrl)
>> +{
>> +    struct nvme_loop_ctrl *ctrl = to_loop_ctrl(nctrl);
>> +
>> +    list_del(&ctrl->list);
>
> This should be list_del_init so that cleanup_module
> list_empty() check will be correct. unloading nvme-loop
> with active controllers is getting a list corruption.

Actually this is wrong. Whats wrong here is that ctrl->list
is being removed twice (once in nvme_loop_cleanup_module and
then here).

The following worked for me:
--
diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c
index a0eac07..cf0f745 100644
--- a/drivers/nvme/target/loop.c
+++ b/drivers/nvme/target/loop.c
@@ -869,18 +869,11 @@ out:

  static void __exit nvme_loop_cleanup_module(void)
  {
-       struct nvme_loop_ctrl *ctrl;
+       struct nvme_loop_ctrl *ctrl, *tmp;

         mutex_lock(&nvme_loop_ctrl_mutex);
-       while (!list_empty(&nvme_loop_ctrl_list)) {
-               ctrl = list_entry(nvme_loop_ctrl_list.next,
-                               struct nvme_loop_ctrl, list);
-
-               if (!list_empty(&ctrl->list))
-                       list_del(&ctrl->list);
-
+       list_for_each_entry_safe(ctrl, tmp, &nvme_loop_ctrl_list, list)
                 __nvme_loop_remove_ctrl(ctrl);
-       }
         mutex_unlock(&nvme_loop_ctrl_mutex);

         device_destroy(nvme_loop_class, MKDEV(0, 0));
--

[PATCH 8/8] nvme-loop: add a NVMe loopback device

[Christoph Hellwig]

On Sun, Nov 08, 2015@03:22:11PM +0200, Sagi Grimberg wrote:
> Actually this is wrong. Whats wrong here is that ctrl->list
> is being removed twice (once in nvme_loop_cleanup_module and
> then here).

Yes, this looks fine.

[PATCH 8/8] nvme-loop: add a NVMe loopback device

[Sagi Grimberg]

> +	ctrl->queue_count = 1; /* admin queue */;
> +	if (nr_io_queues > 0)
> +		ctrl->queue_count += nr_io_queues;
> +	else
> +		ctrl->queue_count += num_possible_cpus();

This should really be num_online_cpus(), I get way more than
I need with num_possible_cpus()...

[PATCH 8/8] nvme-loop: add a NVMe loopback device

[Christoph Hellwig]

On Sun, Nov 15, 2015@09:18:34PM +0200, Sagi Grimberg wrote:
>
>> +	ctrl->queue_count = 1; /* admin queue */;
>> +	if (nr_io_queues > 0)
>> +		ctrl->queue_count += nr_io_queues;
>> +	else
>> +		ctrl->queue_count += num_possible_cpus();
>
> This should really be num_online_cpus(), I get way more than
> I need with num_possible_cpus()...

Maybe.  But then we'd want a hot plug event.  The whole number of
contexts thing is a bit of a mess.

[PATCH 8/8] nvme-loop: add a NVMe loopback device

[Sagi Grimberg]

On 16/11/2015 10:29, Christoph Hellwig wrote:
> On Sun, Nov 15, 2015@09:18:34PM +0200, Sagi Grimberg wrote:
>>
>>> +	ctrl->queue_count = 1; /* admin queue */;
>>> +	if (nr_io_queues > 0)
>>> +		ctrl->queue_count += nr_io_queues;
>>> +	else
>>> +		ctrl->queue_count += num_possible_cpus();
>>
>> This should really be num_online_cpus(), I get way more than
>> I need with num_possible_cpus()...
>
> Maybe.  But then we'd want a hot plug event.  The whole number of
> contexts thing is a bit of a mess.

Or we can just remain with more or less queues then cpus... it is
already possible if the user used nr_io_queues != num_online_cpus()...

[RFC] generic NVMe target and NVMe loop driver

[Nicholas A. Bellinger]

On Sat, 2015-11-07@18:00 +0100, Christoph Hellwig wrote:
> This series continues the NVMe host drive split and also starts adding a
> consume for it.  The consumer is mostly interesting for developers at this
> point as it's simply a 'loopback' NVMe device that ties the split NVMe
> driver fronted into the new generic NVMe target subsystem.

Very excited to see this code posted.  8-)

> This was developed for our NVMe over Fabrics prototype, but will also be useful for
> other work like Ming's virtio-nvme or event an implementation traditional
> PCIe NVMe using vhost.
> 

Wrt to vhost-nvme, the WIP code (Dr. Hannes + Dave CC'ed) I'm currently
hacking on is here:

https://git.kernel.org/cgit/linux/kernel/git/nab/target-pending.git/log/?h=vhost-nvme-wip

Note it's still a week or two away (using rts-megasas as a reference)
from actually functioning across a modest number of queue resources, but
should at least give interested folks an idea of how things look so far.

> The biggest gap at this point is aborts and resets, which are still under
> heavy development.  Once those are done and I've finished the configfs
> layout the code will hopefully be ready for inclusion in Linux 4.5.
> 
> I've also written a python based shell to ease configuration of the target
> subsystem which I'll hopefully be able to release soon.
> 

;)

> As this depends on a lot of pending NVMe patch a git tree is also
> available:
> 
> 	http://git.infradead.org/users/hch/block.git/shortlog/refs/heads/nvme-loop.2
> 

So on vhost-nvme configfs side, my initial code will be using
target_core_fabric_configfs.c to process incoming nvme-hi frames
into existing backend struct se_device.

That said, I'm planning to rebase atop your WIP tree in the short-term
for the common nvme opcode + command set decoding bits, that both
vhost-nvme and nvme-fabrics code are going to require.

--nab

[RFC] generic NVMe target and NVMe loop driver

[Ming Lin]

On Sun, 2015-11-15@23:30 -0800, Nicholas A. Bellinger wrote:
> On Sat, 2015-11-07@18:00 +0100, Christoph Hellwig wrote:
> > This series continues the NVMe host drive split and also starts adding a
> > consume for it.  The consumer is mostly interesting for developers at this
> > point as it's simply a 'loopback' NVMe device that ties the split NVMe
> > driver fronted into the new generic NVMe target subsystem.
> 
> Very excited to see this code posted.  8-)
> 
> > This was developed for our NVMe over Fabrics prototype, but will also be useful for
> > other work like Ming's virtio-nvme or event an implementation traditional
> > PCIe NVMe using vhost.
> > 
> 
> Wrt to vhost-nvme, the WIP code (Dr. Hannes + Dave CC'ed) I'm currently
> hacking on is here:
> 
> https://git.kernel.org/cgit/linux/kernel/git/nab/target-pending.git/log/?h=vhost-nvme-wip
> 
> Note it's still a week or two away (using rts-megasas as a reference)
> from actually functioning across a modest number of queue resources, but
> should at least give interested folks an idea of how things look so far.

Hi Nic,

FYI,

I have done the vhost-nvme patches(based on our previous discussion) on
top of NVMe target.

I'll post kernel & qemu patches early this week.

But the tests I have done so far didn't show competitive performance
compared with vhost-scsi. Maybe because the mmio thing is slow.

I'm going to do anther implementation with virtio-nvme/vhost-nvme.
With nvme-split, now virtio-nvme seems make sense.

I have ported virtio-nvme last month.
https://git.kernel.org/cgit/linux/kernel/git/mlin/linux.git/log/?h=nvme-split/virtio 

Thanks,
Ming

> 
> > The biggest gap at this point is aborts and resets, which are still under
> > heavy development.  Once those are done and I've finished the configfs
> > layout the code will hopefully be ready for inclusion in Linux 4.5.
> > 
> > I've also written a python based shell to ease configuration of the target
> > subsystem which I'll hopefully be able to release soon.
> > 
> 
> ;)
> 
> > As this depends on a lot of pending NVMe patch a git tree is also
> > available:
> > 
> > 	http://git.infradead.org/users/hch/block.git/shortlog/refs/heads/nvme-loop.2
> > 
> 
> So on vhost-nvme configfs side, my initial code will be using
> target_core_fabric_configfs.c to process incoming nvme-hi frames
> into existing backend struct se_device.
> 
> That said, I'm planning to rebase atop your WIP tree in the short-term
> for the common nvme opcode + command set decoding bits, that both
> vhost-nvme and nvme-fabrics code are going to require.
> 
> --nab

[RFC] generic NVMe target and NVMe loop driver

[Nicholas A. Bellinger]

On Mon, 2015-11-16@00:08 -0800, Ming Lin wrote:
> On Sun, 2015-11-15@23:30 -0800, Nicholas A. Bellinger wrote:
> > On Sat, 2015-11-07@18:00 +0100, Christoph Hellwig wrote:
> > > This series continues the NVMe host drive split and also starts adding a
> > > consume for it.  The consumer is mostly interesting for developers at this
> > > point as it's simply a 'loopback' NVMe device that ties the split NVMe
> > > driver fronted into the new generic NVMe target subsystem.
> > 
> > Very excited to see this code posted.  8-)
> > 
> > > This was developed for our NVMe over Fabrics prototype, but will also be useful for
> > > other work like Ming's virtio-nvme or event an implementation traditional
> > > PCIe NVMe using vhost.
> > > 
> > 
> > Wrt to vhost-nvme, the WIP code (Dr. Hannes + Dave CC'ed) I'm currently
> > hacking on is here:
> > 
> > https://git.kernel.org/cgit/linux/kernel/git/nab/target-pending.git/log/?h=vhost-nvme-wip
> > 
> > Note it's still a week or two away (using rts-megasas as a reference)
> > from actually functioning across a modest number of queue resources, but
> > should at least give interested folks an idea of how things look so far.
> 
> Hi Nic,
> 
> FYI,
> 
> I have done the vhost-nvme patches(based on our previous discussion) on
> top of NVMe target.
> 
> I'll post kernel & qemu patches early this week.
> 

Great.  Looking forward to seeing the prototype code.

> But the tests I have done so far didn't show competitive performance
> compared with vhost-scsi. Maybe because the mmio thing is slow.
> 

Anything interesting hot-spots that show up in perf output..?

> I'm going to do anther implementation with virtio-nvme/vhost-nvme.
> With nvme-split, now virtio-nvme seems make sense.
> 
> I have ported virtio-nvme last month.
> https://git.kernel.org/cgit/linux/kernel/git/mlin/linux.git/log/?h=nvme-split/virtio 

Cool.  :)

[RFC] generic NVMe target and NVMe loop driver

[Ming Lin]

On Mon, 2015-11-16@00:29 -0800, Nicholas A. Bellinger wrote:
> On Mon, 2015-11-16@00:08 -0800, Ming Lin wrote:
> > On Sun, 2015-11-15@23:30 -0800, Nicholas A. Bellinger wrote:
> > > On Sat, 2015-11-07@18:00 +0100, Christoph Hellwig wrote:
> > > > This series continues the NVMe host drive split and also starts adding a
> > > > consume for it.  The consumer is mostly interesting for developers at this
> > > > point as it's simply a 'loopback' NVMe device that ties the split NVMe
> > > > driver fronted into the new generic NVMe target subsystem.
> > > 
> > > Very excited to see this code posted.  8-)
> > > 
> > > > This was developed for our NVMe over Fabrics prototype, but will also be useful for
> > > > other work like Ming's virtio-nvme or event an implementation traditional
> > > > PCIe NVMe using vhost.
> > > > 
> > > 
> > > Wrt to vhost-nvme, the WIP code (Dr. Hannes + Dave CC'ed) I'm currently
> > > hacking on is here:
> > > 
> > > https://git.kernel.org/cgit/linux/kernel/git/nab/target-pending.git/log/?h=vhost-nvme-wip
> > > 
> > > Note it's still a week or two away (using rts-megasas as a reference)
> > > from actually functioning across a modest number of queue resources, but
> > > should at least give interested folks an idea of how things look so far.
> > 
> > Hi Nic,
> > 
> > FYI,
> > 
> > I have done the vhost-nvme patches(based on our previous discussion) on
> > top of NVMe target.
> > 
> > I'll post kernel & qemu patches early this week.
> > 
> 
> Great.  Looking forward to seeing the prototype code.
> 
> > But the tests I have done so far didn't show competitive performance
> > compared with vhost-scsi. Maybe because the mmio thing is slow.
> > 
> 
> Anything interesting hot-spots that show up in perf output..?

To ease development, I use nested kvm.
"vm_host" runs on bare metal and "vm_guest" runs on "vm_host"

I just integrated Google's extension to vhost-nvme.
https://github.com/rlnelson-git/linux-nvme.git

It's amazing performance improves a lot. 
I use a 256M /dev/ram0 on vm_host as backend.

fio 4k read:
qemu-nvme: ~20M to ~30M
qemu-vhost-nvme + google ext: 80M to 200M(not very stable though)

(BTW, still waiting for employer's approval to send out patches)

   PerfTop:    1039 irqs/sec  kernel:99.8%  exact:  0.0% [4000Hz cpu-clock],  (all, 4 CPUs)
---------------------------------------------------------------------------------------------
    36.93%  [kernel]       [k] _raw_spin_unlock_irq          
    20.98%  [kernel]       [k] vmx_handle_external_intr      
    10.10%  [kernel]       [k] _raw_spin_unlock_irqrestore   
     4.95%  [kernel]       [k] __mutex_unlock_slowpath       
     4.41%  [kernel]       [k] lock_acquire                  
     4.15%  [kernel]       [k] lock_is_held                  
     2.30%  [kernel]       [k] mutex_lock_nested             
     1.68%  [kernel]       [k] lock_release                  
     1.14%  [kernel]       [k] put_compound_page             
     0.93%  [kernel]       [k] debug_lockdep_rcu_enabled     
     0.66%  [kernel]       [k] check_preemption_disabled     
     0.64%  [kernel]       [k] __schedule                    
     0.62%  [kernel]       [k] lock_acquired                 
     0.54%  [kernel]       [k] rcu_lockdep_current_cpu_online
     0.54%  [kernel]       [k] preempt_count_sub             
     0.54%  [kernel]       [k] preempt_count_add             
     0.46%  [kernel]       [k] find_vma                      
     0.45%  [kernel]       [k] vmcs_writel                   
     0.40%  [kernel]       [k] ___might_sleep                
     0.38%  [kernel]       [k] rcu_note_context_switch       
     0.37%  [kernel]       [k] rcu_read_lock_sched_held      
     0.32%  [kernel]       [k] __rcu_is_watching             
     0.32%  [kernel]       [k] follow_trans_huge_pmd         
     0.31%  [kernel]       [k] debug_smp_processor_id        
     0.22%  [kernel]       [k] follow_page_mask              
     0.18%  [kernel]       [k] __get_user_pages              
     0.16%  [kernel]       [k] vmx_read_guest_seg_ar         
     0.16%  [kernel]       [k] nvmet_vhost_rw                
     0.15%  [kernel]       [k] kthread_should_stop           
     0.14%  [kernel]       [k] schedule                      
     0.14%  [kernel]       [k] rcu_is_watching               
     0.12%  [kernel]       [k] nvmet_vhost_sq_thread         
     0.11%  [kernel]       [k] get_parent_ip                 
     0.11%  [kernel]       [k] _raw_spin_lock_irqsave   

[RFC] generic NVMe target and NVMe loop driver

[Christoph Hellwig]

On Mon, Nov 16, 2015@12:08:58AM -0800, Ming Lin wrote:
> But the tests I have done so far didn't show competitive performance
> compared with vhost-scsi. Maybe because the mmio thing is slow.

It is.  Take a look at the google patches for the NVMe even index
extension, which make it behave a lot more like virtio.