Commit b810253b authored by Philippe Bergheaud's avatar Philippe Bergheaud Committed by Michael Ellerman
Browse files

cxl: Add mechanism for delivering AFU driver specific events 



This adds an afu_driver_ops structure with fetch_event() and
event_delivered() callbacks. An AFU driver such as cxlflash can fill
this out and associate it with a context to enable passing custom AFU
specific events to userspace.

This also adds a new kernel API function cxl_context_pending_events(),
that the AFU driver can use to notify the cxl driver that new specific
events are ready to be delivered, and wake up anyone waiting on the
context wait queue.

The current count of AFU driver specific events is stored in the field
afu_driver_events of the context structure.

The cxl driver checks the afu_driver_events count during poll, select,
read, etc. calls to check if an AFU driver specific event is pending,
and calls fetch_event() to obtain and deliver that event. This way, the
cxl driver takes care of all the usual locking semantics around these
calls and handles all the generic cxl events, so that the AFU driver
only needs to worry about it's own events.

fetch_event() return a struct cxl_event_afu_driver_reserved, allocated
by the AFU driver, and filled in with the specific event information and
size. Total event size (header + data) should not be greater than
CXL_READ_MIN_SIZE (4K).

Th cxl driver prepends an appropriate cxl event header, copies the event
to userspace, and finally calls event_delivered() to return the status of
the operation to the AFU driver. The event is identified by the context
and cxl_event_afu_driver_reserved pointers.

Since AFU drivers provide their own means for userspace to obtain the
AFU file descriptor (i.e. cxlflash uses an ioctl on their scsi file
descriptor to obtain the AFU file descriptor) and the generic cxl driver
will never use this event, the ABI of the event is up to each individual
AFU driver.

Signed-off-by: default avatarPhilippe Bergheaud <felix@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 6e8a9279

drivers/misc/cxl/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -15,12 +15,17 @@ config CXL_EEH 
	bool

	default n



config CXL_AFU_DRIVER_OPS

	bool

	default n



config CXL

	tristate "Support for IBM Coherent Accelerators (CXL)"

	depends on PPC_POWERNV && PCI_MSI && EEH

	select CXL_BASE

	select CXL_KERNEL_API

	select CXL_EEH

	select CXL_AFU_DRIVER_OPS

	default m

	help

	  Select this option to enable driver support for IBM Coherent

drivers/misc/cxl/api.c

+17 −0
Original line number Diff line number Diff line
@@ -333,6 +333,23 @@ struct cxl_context *cxl_fops_get_context(struct file *file) 
}

EXPORT_SYMBOL_GPL(cxl_fops_get_context);



void cxl_set_driver_ops(struct cxl_context *ctx,

			struct cxl_afu_driver_ops *ops)

{

	WARN_ON(!ops->fetch_event || !ops->event_delivered);

	atomic_set(&ctx->afu_driver_events, 0);

	ctx->afu_driver_ops = ops;

}

EXPORT_SYMBOL_GPL(cxl_set_driver_ops);



void cxl_context_events_pending(struct cxl_context *ctx,

				unsigned int new_events)

{

	atomic_add(new_events, &ctx->afu_driver_events);

	wake_up_all(&ctx->wq);

}

EXPORT_SYMBOL_GPL(cxl_context_events_pending);



int cxl_start_work(struct cxl_context *ctx,

		   struct cxl_ioctl_start_work *work)

{

drivers/misc/cxl/cxl.h

+6 −1
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 
#include <asm/reg.h>

#include <misc/cxl-base.h>



#include <misc/cxl.h>

#include <uapi/misc/cxl.h>



extern uint cxl_verbose;
@@ -34,7 +35,7 @@ extern uint cxl_verbose; 
 * Bump version each time a user API change is made, whether it is

 * backwards compatible ot not.

 */

#define CXL_API_VERSION 2

#define CXL_API_VERSION 3

#define CXL_API_VERSION_COMPATIBLE 1



/*
@@ -528,6 +529,10 @@ struct cxl_context { 
	bool pending_fault;

	bool pending_afu_err;



	/* Used by AFU drivers for driver specific event delivery */

	struct cxl_afu_driver_ops *afu_driver_ops;

	atomic_t afu_driver_events;



	struct rcu_head rcu;

};

drivers/misc/cxl/file.c

+56 −8
Original line number Diff line number Diff line
@@ -293,6 +293,17 @@ int afu_mmap(struct file *file, struct vm_area_struct *vm) 
	return cxl_context_iomap(ctx, vm);

}



static inline bool ctx_event_pending(struct cxl_context *ctx)

{

	if (ctx->pending_irq || ctx->pending_fault || ctx->pending_afu_err)

		return true;



	if (ctx->afu_driver_ops && atomic_read(&ctx->afu_driver_events))

		return true;



	return false;

}



unsigned int afu_poll(struct file *file, struct poll_table_struct *poll)

{

	struct cxl_context *ctx = file->private_data;
@@ -305,8 +316,7 @@ unsigned int afu_poll(struct file *file, struct poll_table_struct *poll) 
	pr_devel("afu_poll wait done pe: %i\n", ctx->pe);



	spin_lock_irqsave(&ctx->lock, flags);

	if (ctx->pending_irq || ctx->pending_fault ||

	    ctx->pending_afu_err)

	if (ctx_event_pending(ctx))

		mask |= POLLIN | POLLRDNORM;

	else if (ctx->status == CLOSED)

		/* Only error on closed when there are no futher events pending
@@ -319,16 +329,46 @@ unsigned int afu_poll(struct file *file, struct poll_table_struct *poll) 
	return mask;

}



static inline int ctx_event_pending(struct cxl_context *ctx)

static ssize_t afu_driver_event_copy(struct cxl_context *ctx,

				     char __user *buf,

				     struct cxl_event *event,

				     struct cxl_event_afu_driver_reserved *pl)

{

	return (ctx->pending_irq || ctx->pending_fault ||

	    ctx->pending_afu_err || (ctx->status == CLOSED));

	/* Check event */

	if (!pl) {

		ctx->afu_driver_ops->event_delivered(ctx, pl, -EINVAL);

		return -EFAULT;

	}



	/* Check event size */

	event->header.size += pl->data_size;

	if (event->header.size > CXL_READ_MIN_SIZE) {

		ctx->afu_driver_ops->event_delivered(ctx, pl, -EINVAL);

		return -EFAULT;

	}



	/* Copy event header */

	if (copy_to_user(buf, event, sizeof(struct cxl_event_header))) {

		ctx->afu_driver_ops->event_delivered(ctx, pl, -EFAULT);

		return -EFAULT;

	}



	/* Copy event data */

	buf += sizeof(struct cxl_event_header);

	if (copy_to_user(buf, &pl->data, pl->data_size)) {

		ctx->afu_driver_ops->event_delivered(ctx, pl, -EFAULT);

		return -EFAULT;

	}



	ctx->afu_driver_ops->event_delivered(ctx, pl, 0); /* Success */

	return event->header.size;

}



ssize_t afu_read(struct file *file, char __user *buf, size_t count,

			loff_t *off)

{

	struct cxl_context *ctx = file->private_data;

	struct cxl_event_afu_driver_reserved *pl = NULL;

	struct cxl_event event;

	unsigned long flags;

	int rc;
@@ -344,7 +384,7 @@ ssize_t afu_read(struct file *file, char __user *buf, size_t count, 


	for (;;) {

		prepare_to_wait(&ctx->wq, &wait, TASK_INTERRUPTIBLE);

		if (ctx_event_pending(ctx))

		if (ctx_event_pending(ctx) || (ctx->status == CLOSED))

			break;



		if (!cxl_ops->link_ok(ctx->afu->adapter, ctx->afu)) {
@@ -374,7 +414,12 @@ ssize_t afu_read(struct file *file, char __user *buf, size_t count, 
	memset(&event, 0, sizeof(event));

	event.header.process_element = ctx->pe;

	event.header.size = sizeof(struct cxl_event_header);

	if (ctx->pending_irq) {

	if (ctx->afu_driver_ops && atomic_read(&ctx->afu_driver_events)) {

		pr_devel("afu_read delivering AFU driver specific event\n");

		pl = ctx->afu_driver_ops->fetch_event(ctx);

		atomic_dec(&ctx->afu_driver_events);

		event.header.type = CXL_EVENT_AFU_DRIVER;

	} else if (ctx->pending_irq) {

		pr_devel("afu_read delivering AFU interrupt\n");

		event.header.size += sizeof(struct cxl_event_afu_interrupt);

		event.header.type = CXL_EVENT_AFU_INTERRUPT;
@@ -404,6 +449,9 @@ ssize_t afu_read(struct file *file, char __user *buf, size_t count, 


	spin_unlock_irqrestore(&ctx->lock, flags);



	if (event.header.type == CXL_EVENT_AFU_DRIVER)

		return afu_driver_event_copy(ctx, buf, &event, pl);



	if (copy_to_user(buf, &event, event.header.size))

		return -EFAULT;

	return event.header.size;
@@ -558,7 +606,7 @@ int __init cxl_file_init(void) 
	 * If these change we really need to update API.  Either change some

	 * flags or update API version number CXL_API_VERSION.

	 */

	BUILD_BUG_ON(CXL_API_VERSION != 2);

	BUILD_BUG_ON(CXL_API_VERSION != 3);

	BUILD_BUG_ON(sizeof(struct cxl_ioctl_start_work) != 64);

	BUILD_BUG_ON(sizeof(struct cxl_event_header) != 8);

	BUILD_BUG_ON(sizeof(struct cxl_event_afu_interrupt) != 8);

include/misc/cxl.h

+48 −0
Original line number Diff line number Diff line
@@ -220,4 +220,52 @@ void cxl_perst_reloads_same_image(struct cxl_afu *afu, 
 */

ssize_t cxl_read_adapter_vpd(struct pci_dev *dev, void *buf, size_t count);



/*

 * AFU driver ops allow an AFU driver to create their own events to pass to

 * userspace through the file descriptor as a simpler alternative to overriding

 * the read() and poll() calls that works with the generic cxl events. These

 * events are given priority over the generic cxl events, so they will be

 * delivered first if multiple types of events are pending.

 *

 * The AFU driver must call cxl_context_events_pending() to notify the cxl

 * driver that new events are ready to be delivered for a specific context.

 * cxl_context_events_pending() will adjust the current count of AFU driver

 * events for this context, and wake up anyone waiting on the context wait

 * queue.

 *

 * The cxl driver will then call fetch_event() to get a structure defining

 * the size and address of the driver specific event data. The cxl driver

 * will build a cxl header with type and process_element fields filled in,

 * and header.size set to sizeof(struct cxl_event_header) + data_size.

 * The total size of the event is limited to CXL_READ_MIN_SIZE (4K).

 *

 * fetch_event() is called with a spin lock held, so it must not sleep.

 *

 * The cxl driver will then deliver the event to userspace, and finally

 * call event_delivered() to return the status of the operation, identified

 * by cxl context and AFU driver event data pointers.

 *   0        Success

 *   -EFAULT  copy_to_user() has failed

 *   -EINVAL  Event data pointer is NULL, or event size is greater than

 *            CXL_READ_MIN_SIZE.

 */

struct cxl_afu_driver_ops {

	struct cxl_event_afu_driver_reserved *(*fetch_event) (

						struct cxl_context *ctx);

	void (*event_delivered) (struct cxl_context *ctx,

				 struct cxl_event_afu_driver_reserved *event,

				 int rc);

};



/*

 * Associate the above driver ops with a specific context.

 * Reset the current count of AFU driver events.

 */

void cxl_set_driver_ops(struct cxl_context *ctx,

			struct cxl_afu_driver_ops *ops);



/* Notify cxl driver that new events are ready to be delivered for context */

void cxl_context_events_pending(struct cxl_context *ctx,

				unsigned int new_events);



#endif /* _MISC_CXL_H */

CRA Git | Maintained and supported by SUSTech CRA and CCSE