Re: [PATCH v2 5/5] vfio-ccw: add handling for async channel instructions

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On 01/21/2019 06:03 AM, Cornelia Huck wrote:
Add a region to the vfio-ccw device that can be used to submit
asynchronous I/O instructions. ssch continues to be handled by the
existing I/O region; the new region handles hsch and csch.

Interrupt status continues to be reported through the same channels
as for ssch.

Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx>
---
  drivers/s390/cio/Makefile           |   3 +-
  drivers/s390/cio/vfio_ccw_async.c   |  91 ++++++++++++++++++++++
  drivers/s390/cio/vfio_ccw_drv.c     |  45 +++++++----
  drivers/s390/cio/vfio_ccw_fsm.c     | 114 +++++++++++++++++++++++++++-
  drivers/s390/cio/vfio_ccw_ops.c     |  13 +++-
  drivers/s390/cio/vfio_ccw_private.h |   9 ++-
  include/uapi/linux/vfio.h           |   2 +
  include/uapi/linux/vfio_ccw.h       |  12 +++
  8 files changed, 269 insertions(+), 20 deletions(-)
  create mode 100644 drivers/s390/cio/vfio_ccw_async.c

diff --git a/drivers/s390/cio/Makefile b/drivers/s390/cio/Makefile
index f230516abb96..f6a8db04177c 100644
--- a/drivers/s390/cio/Makefile
+++ b/drivers/s390/cio/Makefile
@@ -20,5 +20,6 @@ obj-$(CONFIG_CCWGROUP) += ccwgroup.o
  qdio-objs := qdio_main.o qdio_thinint.o qdio_debug.o qdio_setup.o
  obj-$(CONFIG_QDIO) += qdio.o
-vfio_ccw-objs += vfio_ccw_drv.o vfio_ccw_cp.o vfio_ccw_ops.o vfio_ccw_fsm.o
+vfio_ccw-objs += vfio_ccw_drv.o vfio_ccw_cp.o vfio_ccw_ops.o vfio_ccw_fsm.o \
+	vfio_ccw_async.o
  obj-$(CONFIG_VFIO_CCW) += vfio_ccw.o
diff --git a/drivers/s390/cio/vfio_ccw_async.c b/drivers/s390/cio/vfio_ccw_async.c
new file mode 100644
index 000000000000..604806c2970f
--- /dev/null
+++ b/drivers/s390/cio/vfio_ccw_async.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Async I/O region for vfio_ccw
+ *
+ * Copyright Red Hat, Inc. 2019
+ *
+ * Author(s): Cornelia Huck <cohuck@xxxxxxxxxx>
+ */
+
+#include <linux/vfio.h>
+#include <linux/mdev.h>
+
+#include "vfio_ccw_private.h"
+
+static ssize_t vfio_ccw_async_region_read(struct vfio_ccw_private *private,
+					  char __user *buf, size_t count,
+					  loff_t *ppos)
+{
+	unsigned int i = VFIO_CCW_OFFSET_TO_INDEX(*ppos) - VFIO_CCW_NUM_REGIONS;
+	loff_t pos = *ppos & VFIO_CCW_OFFSET_MASK;
+	struct ccw_cmd_region *region;
+	int ret;
+
+	if (pos + count > sizeof(*region))
+		return -EINVAL;
+
+	mutex_lock(&private->io_mutex);
+	region = private->region[i].data;
+	if (copy_to_user(buf, (void *)region + pos, count))
+		ret = -EFAULT;
+	else
+		ret = count;
+	mutex_unlock(&private->io_mutex);
+	return ret;
+}
+
+static ssize_t vfio_ccw_async_region_write(struct vfio_ccw_private *private,
+					   const char __user *buf, size_t count,
+					   loff_t *ppos)
+{
+	unsigned int i = VFIO_CCW_OFFSET_TO_INDEX(*ppos) - VFIO_CCW_NUM_REGIONS;
+	loff_t pos = *ppos & VFIO_CCW_OFFSET_MASK;
+	struct ccw_cmd_region *region;
+	int ret;
+
+	if (pos + count > sizeof(*region))
+		return -EINVAL;
+
+	if (private->state == VFIO_CCW_STATE_NOT_OPER ||
+	    private->state == VFIO_CCW_STATE_STANDBY)
+		return -EACCES;
+	if (!mutex_trylock(&private->io_mutex))
+		return -EAGAIN;
+
+	region = private->region[i].data;
+	if (copy_from_user((void *)region + pos, buf, count)) {
+		ret = -EFAULT;
+		goto out_unlock;
+	}
+
+	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_ASYNC_REQ);
+
+	ret = region->ret_code ? region->ret_code : count;
+
+out_unlock:
+	mutex_unlock(&private->io_mutex);
+	return ret;
+}
+
+static void vfio_ccw_async_region_release(struct vfio_ccw_private *private,
+					  struct vfio_ccw_region *region)
+{
+
+}
+
+const struct vfio_ccw_regops vfio_ccw_async_region_ops = {
+	.read = vfio_ccw_async_region_read,
+	.write = vfio_ccw_async_region_write,
+	.release = vfio_ccw_async_region_release,
+};
+
+int vfio_ccw_register_async_dev_regions(struct vfio_ccw_private *private)
+{
+	return vfio_ccw_register_dev_region(private,
+					    VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD,
+					    &vfio_ccw_async_region_ops,
+					    sizeof(struct ccw_cmd_region),
+					    VFIO_REGION_INFO_FLAG_READ |
+					    VFIO_REGION_INFO_FLAG_WRITE,
+					    private->cmd_region);
+}
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 2ef189fe45ed..d807911b8ed5 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -3,9 +3,11 @@
   * VFIO based Physical Subchannel device driver
   *
   * Copyright IBM Corp. 2017
+ * Copyright Red Hat, Inc. 2019
   *
   * Author(s): Dong Jia Shi <bjsdjshi@xxxxxxxxxxxxxxxxxx>
   *            Xiao Feng Ren <renxiaof@xxxxxxxxxxxxxxxxxx>
+ *            Cornelia Huck <cohuck@xxxxxxxxxx>
   */
#include <linux/module.h>
@@ -23,6 +25,7 @@
struct workqueue_struct *vfio_ccw_work_q;
  static struct kmem_cache *vfio_ccw_io_region;
+static struct kmem_cache *vfio_ccw_cmd_region;
/*
   * Helpers
@@ -104,7 +107,7 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
  {
  	struct pmcw *pmcw = &sch->schib.pmcw;
  	struct vfio_ccw_private *private;
-	int ret;
+	int ret = -ENOMEM;
if (pmcw->qf) {
  		dev_warn(&sch->dev, "vfio: ccw: does not support QDIO: %s\n",
@@ -118,10 +121,13 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
private->io_region = kmem_cache_zalloc(vfio_ccw_io_region,
  					       GFP_KERNEL | GFP_DMA);
-	if (!private->io_region) {
-		kfree(private);
-		return -ENOMEM;
-	}
+	if (!private->io_region)
+		goto out_free;
+
+	private->cmd_region = kmem_cache_zalloc(vfio_ccw_cmd_region,
+						GFP_KERNEL | GFP_DMA);
+	if (!private->cmd_region)
+		goto out_free;
private->sch = sch;
  	dev_set_drvdata(&sch->dev, private);
@@ -149,7 +155,10 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
  	cio_disable_subchannel(sch);
  out_free:
  	dev_set_drvdata(&sch->dev, NULL);
-	kmem_cache_free(vfio_ccw_io_region, private->io_region);
+	if (private->cmd_region)
+		kmem_cache_free(vfio_ccw_cmd_region, private->cmd_region);
+	if (private->io_region)
+		kmem_cache_free(vfio_ccw_io_region, private->io_region);

Well, adding the check if private->xxx_region is non-NULL is fine. I'd have made it a separate patch for io_region, but whatever.

Since you're adding that check, you should add the same if statement in vfio_ccw_sch_remove(). And you should certainly call kmem_cache_free(private->cmd_region) there too. :)

  	kfree(private);
  	return ret;
  }
@@ -238,7 +247,7 @@ static struct css_driver vfio_ccw_sch_driver = {
static int __init vfio_ccw_sch_init(void)
  {
-	int ret;
+	int ret = -ENOMEM;
vfio_ccw_work_q = create_singlethread_workqueue("vfio-ccw");
  	if (!vfio_ccw_work_q)
@@ -248,20 +257,30 @@ static int __init vfio_ccw_sch_init(void)
  					sizeof(struct ccw_io_region), 0,
  					SLAB_ACCOUNT, 0,
  					sizeof(struct ccw_io_region), NULL);
-	if (!vfio_ccw_io_region) {
-		destroy_workqueue(vfio_ccw_work_q);
-		return -ENOMEM;
-	}
+	if (!vfio_ccw_io_region)
+		goto out_err;
+
+	vfio_ccw_cmd_region = kmem_cache_create_usercopy("vfio_ccw_cmd_region",
+					sizeof(struct ccw_cmd_region), 0,
+					SLAB_ACCOUNT, 0,
+					sizeof(struct ccw_cmd_region), NULL);
+	if (!vfio_ccw_cmd_region)
+		goto out_err;
isc_register(VFIO_CCW_ISC);
  	ret = css_driver_register(&vfio_ccw_sch_driver);
  	if (ret) {
  		isc_unregister(VFIO_CCW_ISC);
-		kmem_cache_destroy(vfio_ccw_io_region);
-		destroy_workqueue(vfio_ccw_work_q);
+		goto out_err;
  	}
return ret;
+
+out_err:
+	kmem_cache_destroy(vfio_ccw_cmd_region);
+	kmem_cache_destroy(vfio_ccw_io_region);
+	destroy_workqueue(vfio_ccw_work_q);
+	return ret;
  }
static void __exit vfio_ccw_sch_exit(void)
diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
index f6ed934cc565..72912d596181 100644
--- a/drivers/s390/cio/vfio_ccw_fsm.c
+++ b/drivers/s390/cio/vfio_ccw_fsm.c
@@ -3,8 +3,10 @@
   * Finite state machine for vfio-ccw device handling
   *
   * Copyright IBM Corp. 2017
+ * Copyright Red Hat, Inc. 2019
   *
   * Author(s): Dong Jia Shi <bjsdjshi@xxxxxxxxxxxxxxxxxx>
+ *            Cornelia Huck <cohuck@xxxxxxxxxx>
   */
#include <linux/vfio.h>
@@ -69,6 +71,81 @@ static int fsm_io_helper(struct vfio_ccw_private *private)
  	return ret;
  }
+static int fsm_do_halt(struct vfio_ccw_private *private)
+{
+	struct subchannel *sch;
+	unsigned long flags;
+	int ccode;
+	int ret;
+
+	sch = private->sch;
+
+	spin_lock_irqsave(sch->lock, flags);
+
+	/* Issue "Halt Subchannel" */
+	ccode = hsch(sch->schid);
+
+	switch (ccode) {
+	case 0:
+		/*
+		 * Initialize device status information
+		 */
+		sch->schib.scsw.cmd.actl |= SCSW_ACTL_HALT_PEND;
+		ret = 0;
+		private->state = VFIO_CCW_STATE_BUSY;
+		break;
+	case 1:		/* Status pending */
+	case 2:		/* Busy */
+		ret = -EBUSY;
+		break;
+	case 3:		/* Device not operational */
+	{
+		ret = -ENODEV;
+		break;
+	}

Why does cc3 get braces, but no other case does?  (Ditto for clear)

(I guess the answer is "because fsm_io_helper does" but I didn't notice that before either. :-)

+	default:
+		ret = ccode;
+	}
+	spin_unlock_irqrestore(sch->lock, flags);
+	return ret;
+}
+
+static int fsm_do_clear(struct vfio_ccw_private *private)
+{
+	struct subchannel *sch;
+	unsigned long flags;
+	int ccode;
+	int ret;
+
+	sch = private->sch;
+
+	spin_lock_irqsave(sch->lock, flags);
+
+	/* Issue "Clear Subchannel" */
+	ccode = csch(sch->schid);
+
+	switch (ccode) {
+	case 0:
+		/*
+		 * Initialize device status information
+		 */
+		sch->schib.scsw.cmd.actl = SCSW_ACTL_CLEAR_PEND;
+		/* TODO: check what else we might need to clear */
+		ret = 0;
+		private->state = VFIO_CCW_STATE_BUSY;
+		break;
+	case 3:		/* Device not operational */
+	{
+		ret = -ENODEV;
+		break;
+	}
+	default:
+		ret = ccode;
+	}
+	spin_unlock_irqrestore(sch->lock, flags);
+	return ret;
+}
+
  static void fsm_notoper(struct vfio_ccw_private *private,
  			enum vfio_ccw_event event)
  {
@@ -103,6 +180,14 @@ static void fsm_io_busy(struct vfio_ccw_private *private,
  	private->io_region->ret_code = -EAGAIN;
  }
+static void fsm_async_error(struct vfio_ccw_private *private,
+			    enum vfio_ccw_event event)
+{
+	pr_err("vfio-ccw: FSM: halt/clear request from state:%d\n",
+	       private->state);

Had a little deja vu here.  :)

Can this message use private->cmd_region->command to tell us if it's a halt, clear, or unknown? Instead of just saying "halt/clear" statically.

+	private->cmd_region->ret_code = -EIO;
+}
+
  static void fsm_disabled_irq(struct vfio_ccw_private *private,
  			     enum vfio_ccw_event event)
  {
@@ -165,11 +250,11 @@ static void fsm_io_request(struct vfio_ccw_private *private,
  		}
  		return;
  	} else if (scsw->cmd.fctl & SCSW_FCTL_HALT_FUNC) {
-		/* XXX: Handle halt. */
+		/* halt is handled via the async cmd region */
  		io_region->ret_code = -EOPNOTSUPP;
  		goto err_out;
  	} else if (scsw->cmd.fctl & SCSW_FCTL_CLEAR_FUNC) {
-		/* XXX: Handle clear. */
+		/* clear is handled via the async cmd region */
  		io_region->ret_code = -EOPNOTSUPP;
  		goto err_out;
  	}
@@ -179,6 +264,27 @@ static void fsm_io_request(struct vfio_ccw_private *private,
  			       io_region->ret_code, errstr);
  }
+/*
+ * Deal with an async request from userspace.
+ */
+static void fsm_async_request(struct vfio_ccw_private *private,
+			      enum vfio_ccw_event event)
+{
+	struct ccw_cmd_region *cmd_region = private->cmd_region;
+
+	switch (cmd_region->command) {
+	case VFIO_CCW_ASYNC_CMD_HSCH:
+		cmd_region->ret_code = fsm_do_halt(private);
+		break;
+	case VFIO_CCW_ASYNC_CMD_CSCH:
+		cmd_region->ret_code = fsm_do_clear(private);
+		break;
+	default:
+		/* should not happen? */
+		cmd_region->ret_code = -EINVAL;
+	}
+}
+
  /*
   * Got an interrupt for a normal io (state busy).
   */
@@ -202,21 +308,25 @@ fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
  	[VFIO_CCW_STATE_NOT_OPER] = {
  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_nop,
  		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_error,
+		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_error,
  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_disabled_irq,
  	},
  	[VFIO_CCW_STATE_STANDBY] = {
  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
  		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_error,
+		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_error,
  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
  	},
  	[VFIO_CCW_STATE_IDLE] = {
  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
  		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_request,
+		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_request,
  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
  	},
  	[VFIO_CCW_STATE_BUSY] = {
  		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
  		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_busy,
+		[VFIO_CCW_EVENT_ASYNC_REQ]	= fsm_async_request,
  		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
  	},
  };
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index 5a89d09f9271..755806cb8d53 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -148,11 +148,20 @@ static int vfio_ccw_mdev_open(struct mdev_device *mdev)
  	struct vfio_ccw_private *private =
  		dev_get_drvdata(mdev_parent_dev(mdev));
  	unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
+	int ret;
private->nb.notifier_call = vfio_ccw_mdev_notifier; - return vfio_register_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
-				      &events, &private->nb);
+	ret = vfio_register_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
+				     &events, &private->nb);
+	if (ret)
+		return ret;
+
+	ret = vfio_ccw_register_async_dev_regions(private);
+	if (ret)
+		vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
+					 &private->nb);
+	return ret;
  }
static void vfio_ccw_mdev_release(struct mdev_device *mdev)
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 20e75f4f3695..ed8b94ea2f08 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -31,9 +31,9 @@ struct vfio_ccw_private;
  struct vfio_ccw_region;
struct vfio_ccw_regops {
-	size_t	(*read)(struct vfio_ccw_private *private, char __user *buf,
+	ssize_t	(*read)(struct vfio_ccw_private *private, char __user *buf,
  			size_t count, loff_t *ppos);
-	size_t	(*write)(struct vfio_ccw_private *private,
+	ssize_t	(*write)(struct vfio_ccw_private *private,

Ah, amending my r-b to patch 3 :)

  			 const char __user *buf, size_t count, loff_t *ppos);
  	void	(*release)(struct vfio_ccw_private *private,
  			   struct vfio_ccw_region *region);
@@ -53,6 +53,8 @@ int vfio_ccw_register_dev_region(struct vfio_ccw_private *private,
  				 const struct vfio_ccw_regops *ops,
  				 size_t size, u32 flags, void *data);
+int vfio_ccw_register_async_dev_regions(struct vfio_ccw_private *private);
+
  /**
   * struct vfio_ccw_private
   * @sch: pointer to the subchannel
@@ -64,6 +66,7 @@ int vfio_ccw_register_dev_region(struct vfio_ccw_private *private,
   * @io_region: MMIO region to input/output I/O arguments/results
   * @io_mutex: protect against concurrent update of I/O structures
   * @region: additional regions for other subchannel operations
+ * @cmd_region: MMIO region for asynchronous I/O commands other than START
   * @num_regions: number of additional regions
   * @cp: channel program for the current I/O operation
   * @irb: irb info received from interrupt
@@ -81,6 +84,7 @@ struct vfio_ccw_private {
  	struct ccw_io_region	*io_region;
  	struct mutex		io_mutex;
  	struct vfio_ccw_region *region;
+	struct ccw_cmd_region	*cmd_region;
  	int num_regions;
struct channel_program cp;
@@ -115,6 +119,7 @@ enum vfio_ccw_event {
  	VFIO_CCW_EVENT_NOT_OPER,
  	VFIO_CCW_EVENT_IO_REQ,
  	VFIO_CCW_EVENT_INTERRUPT,
+	VFIO_CCW_EVENT_ASYNC_REQ,
  	/* last element! */
  	NR_VFIO_CCW_EVENTS
  };
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 56e2413d3e00..8f10748dac79 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -354,6 +354,8 @@ struct vfio_region_gfx_edid {
  };
#define VFIO_REGION_TYPE_CCW (2)
+/* ccw sub-types */
+#define VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD	(1)
/*
   * 10de vendor sub-type
diff --git a/include/uapi/linux/vfio_ccw.h b/include/uapi/linux/vfio_ccw.h
index 2ec5f367ff78..cbecbf0cd54f 100644
--- a/include/uapi/linux/vfio_ccw.h
+++ b/include/uapi/linux/vfio_ccw.h
@@ -12,6 +12,7 @@
#include <linux/types.h> +/* used for START SUBCHANNEL, always present */
  struct ccw_io_region {
  #define ORB_AREA_SIZE 12
  	__u8	orb_area[ORB_AREA_SIZE];
@@ -22,4 +23,15 @@ struct ccw_io_region {
  	__u32	ret_code;
  } __packed;
+/*
+ * used for processing commands that trigger asynchronous actions
+ * Note: this is controlled by a capability
+ */
+#define VFIO_CCW_ASYNC_CMD_HSCH (1 << 0)
+#define VFIO_CCW_ASYNC_CMD_CSCH (1 << 1)
+struct ccw_cmd_region {
+	__u32 command;
+	__u32 ret_code;
+} __packed;
+
  #endif





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