Re: [RFC PATCH 1/4] cxl/region: Add region creation ABI

[Ben Widawsky <ben.widawsky@intel.com>]

On 21-06-11 14:31:43, Jonathan Cameron wrote:
> On Thu, 10 Jun 2021 11:57:22 -0700
> Ben Widawsky <ben.widawsky@intel.com> wrote:
> 
> > Regions are created as a child of the decoder that encompasses an
> > address space with constraints. Regions only exist for persistent
> > capacities.
> > 
> > As an example, creating a region with:
> > echo 1 > /sys/bus/cxl/devices/decoder1.0/create_region
> > 
> > Will yield /sys/bus/cxl/devices/decoder1.0/region1.0:0
> > 
> > That region may then be deleted with:
> > echo "region1.0:0 > /sys/bus/cxl/devices/decoder1.0/delete_region
> > 
> > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> Minor stuff inline.
> 
> > ---
> >  Documentation/ABI/testing/sysfs-bus-cxl       |  19 +++
> >  .../driver-api/cxl/memory-devices.rst         |   8 +
> >  drivers/cxl/Makefile                          |   2 +-
> >  drivers/cxl/core.c                            |  71 ++++++++
> >  drivers/cxl/cxl.h                             |  11 ++
> >  drivers/cxl/mem.h                             |  19 +++
> >  drivers/cxl/region.c                          | 155 ++++++++++++++++++
> >  7 files changed, 284 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/cxl/region.c
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
> > index 0b6a2e6e8fbb..5bcbefd4ea38 100644
> > --- a/Documentation/ABI/testing/sysfs-bus-cxl
> > +++ b/Documentation/ABI/testing/sysfs-bus-cxl
> > @@ -127,3 +127,22 @@ Description:
> >  		memory (type-3). The 'target_type' attribute indicates the
> >  		current setting which may dynamically change based on what
> >  		memory regions are activated in this decode hierarchy.
> > +
> > +What:		/sys/bus/cxl/devices/decoderX.Y/create_region
> > +Date:		June, 2021
> > +KernelVersion:	v5.14
> > +Contact:	linux-cxl@vger.kernel.org
> > +Description:
> > +		Writing a value of '1' will create a new uninitialized region
> > +		that will be mapped by the CXL decoderX.Y. Reading from this
> > +		node will return the last created region. Regions must be
> > +		subsequently configured and bound to a region driver before they
> > +		can be used.
> > +
> > +What:		/sys/bus/cxl/devices/decoderX.Y/delete_region
> > +Date:		June, 2021
> > +KernelVersion:	v5.14
> > +Contact:	linux-cxl@vger.kernel.org
> > +Description:
> > +		Deletes the named region. A region must be unbound from the
> > +		region driver before being deleted.
> 
> Perhaps call out an example of what a name looks like?
> 
> > diff --git a/Documentation/driver-api/cxl/memory-devices.rst b/Documentation/driver-api/cxl/memory-devices.rst
> > index 487ce4f41d77..3066638b087f 100644
> > --- a/Documentation/driver-api/cxl/memory-devices.rst
> > +++ b/Documentation/driver-api/cxl/memory-devices.rst
> > @@ -39,6 +39,14 @@ CXL Core
> >  .. kernel-doc:: drivers/cxl/core.c
> >     :doc: cxl core
> >  
> > +CXL Regions
> > +-----------
> > +.. kernel-doc:: drivers/cxl/region.c
> > +   :doc: cxl region
> > +
> > +.. kernel-doc:: drivers/cxl/region.c
> > +   :identifiers:
> > +
> >  External Interfaces
> >  ===================
> >  
> > diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile
> > index a29efb3e8ad2..2b9dd9187788 100644
> > --- a/drivers/cxl/Makefile
> > +++ b/drivers/cxl/Makefile
> > @@ -4,6 +4,6 @@ obj-$(CONFIG_CXL_MEM) += cxl_pci.o
> >  obj-$(CONFIG_CXL_ACPI) += cxl_acpi.o
> >  
> >  ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=CXL
> > -cxl_core-y := core.o
> > +cxl_core-y := core.o region.o
> >  cxl_pci-y := pci.o
> >  cxl_acpi-y := acpi.o
> > diff --git a/drivers/cxl/core.c b/drivers/cxl/core.c
> > index 1b9ee0b08384..cda09a9cd98e 100644
> > --- a/drivers/cxl/core.c
> > +++ b/drivers/cxl/core.c
> > @@ -7,6 +7,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/idr.h>
> >  #include "cxl.h"
> > +#include "mem.h"
> 
> This seems to be breaking the nice separation in cxl.
> Perhaps add a region.h instead?
> 
> >  
> >  /**
> >   * DOC: cxl core
> > @@ -119,7 +120,68 @@ static ssize_t target_list_show(struct device *dev,
> >  }
> >  static DEVICE_ATTR_RO(target_list);
> >  
> > +static ssize_t create_region_show(struct device *dev,
> > +				  struct device_attribute *attr, char *buf)
> > +{
> > +	struct cxl_decoder *cxld = to_cxl_decoder(dev);
> > +	int rc;
> > +
> > +	device_lock(dev);
> > +	rc = sprintf(buf, "%s\n",
> > +		     cxld->youngest ? dev_name(&cxld->youngest->dev) : "");
> > +	device_unlock(dev);
> > +
> > +	return rc;
> > +}
> > +
> > +static ssize_t create_region_store(struct device *dev,
> > +				   struct device_attribute *attr,
> > +				   const char *buf, size_t len)
> > +{
> > +	struct cxl_decoder *cxld = to_cxl_decoder(dev);
> > +	struct cxl_region *region;
> > +	ssize_t rc;
> > +	int val;
> > +
> > +	rc = kstrtoint(buf, 0, &val);
> > +	if (rc)
> > +		return rc;
> > +	if (val != 1)
> > +		return -EINVAL;
> > +
> > +	region = cxl_alloc_region(cxld);
> > +	if (IS_ERR(region))
> > +		return PTR_ERR(region);
> > +
> > +	rc = cxl_add_region(cxld, region);
> > +	if (rc) {
> > +		cxl_free_region(cxld, region);
> > +		return rc;
> > +	}
> > +
> > +	cxld->youngest = region;
> 
> Care needed I think if a delete is called on whatever
> is the youngest region then this file read.
> 

I took all your other feedback, thanks. Good catch here. I *intended* youngest to
be racy (for simplicity sake, since it's informational only), but as it stands
here, it can oops.

> > +	return len;
> > +}
> > +static DEVICE_ATTR_RW(create_region);
> > +
> > +static ssize_t delete_region_store(struct device *dev,
> > +				   struct device_attribute *attr,
> > +				   const char *buf, size_t len)
> > +{
> > +	struct cxl_decoder *cxld = to_cxl_decoder(dev);
> > +	int rc;
> > +
> > +	rc = cxl_delete_region(cxld, buf);
> > +	if (rc)
> > +		return rc;
> > +
> > +	return len;
> > +}
> > +static DEVICE_ATTR_WO(delete_region);
> > +
> >  static struct attribute *cxl_decoder_base_attrs[] = {
> > +	&dev_attr_create_region.attr,
> > +	&dev_attr_delete_region.attr,
> >  	&dev_attr_start.attr,
> >  	&dev_attr_size.attr,
> >  	&dev_attr_locked.attr,
> > @@ -170,7 +232,13 @@ static void cxl_decoder_release(struct device *dev)
> >  {
> >  	struct cxl_decoder *cxld = to_cxl_decoder(dev);
> >  	struct cxl_port *port = to_cxl_port(dev->parent);
> > +	struct cxl_region *region;
> >  
> > +	list_for_each_entry(region, &cxld->regions, list) {
> > +		cxl_delete_region(cxld, dev_name(&region->dev));
> > +	}
> 
> Nitpick, brackets not needed.
> 
> > +	dev_WARN_ONCE(dev, !ida_is_empty(&cxld->region_ida),
> > +		      "Lost track of a region");
> >  	ida_free(&port->decoder_ida, cxld->id);
> >  	kfree(cxld);
> >  }
> > @@ -475,8 +543,11 @@ cxl_decoder_alloc(struct cxl_port *port, int nr_targets, resource_size_t base,
> >  		.interleave_ways = interleave_ways,
> >  		.interleave_granularity = interleave_granularity,
> >  		.target_type = type,
> > +		.regions = LIST_HEAD_INIT(cxld->regions),
> >  	};
> >  
> > +	ida_init(&cxld->region_ida);
> > +
> >  	/* handle implied target_list */
> >  	if (interleave_ways == 1)
> >  		cxld->target[0] =
> > diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> > index b988ea288f53..1ffc5e07e24d 100644
> > --- a/drivers/cxl/cxl.h
> > +++ b/drivers/cxl/cxl.h
> > @@ -7,6 +7,7 @@
> >  #include <linux/bitfield.h>
> >  #include <linux/bitops.h>
> >  #include <linux/io.h>
> > +#include <linux/uuid.h>
> >  
> >  /**
> >   * DOC: cxl objects
> > @@ -182,6 +183,9 @@ enum cxl_decoder_type {
> >   * @interleave_granularity: data stride per dport
> >   * @target_type: accelerator vs expander (type2 vs type3) selector
> >   * @flags: memory type capabilities and locking
> > + * @region_ida: allocator for region ids.
> > + * @regions: List of regions mapped (may be disabled) by this decoder.
> > + * @youngest: Last region created for this decoder.
> >   * @target: active ordered target list in current decoder configuration
> >   */
> >  struct cxl_decoder {
> > @@ -192,6 +196,9 @@ struct cxl_decoder {
> >  	int interleave_granularity;
> >  	enum cxl_decoder_type target_type;
> >  	unsigned long flags;
> > +	struct ida region_ida;
> > +	struct list_head regions;
> > +	struct cxl_region *youngest;
> >  	struct cxl_dport *target[];
> >  };
> >  
> > @@ -231,6 +238,10 @@ struct cxl_dport {
> >  	struct list_head list;
> >  };
> >  
> > +struct cxl_region *cxl_alloc_region(struct cxl_decoder *cxld);
> > +void cxl_free_region(struct cxl_decoder *cxld, struct cxl_region *region);
> > +int cxl_add_region(struct cxl_decoder *cxld, struct cxl_region *region);
> > +int cxl_delete_region(struct cxl_decoder *cxld, const char *region);
> >  struct cxl_port *to_cxl_port(struct device *dev);
> >  struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
> >  				   resource_size_t component_reg_phys,
> > diff --git a/drivers/cxl/mem.h b/drivers/cxl/mem.h
> > index 13868ff7cadf..4c4eb06a966b 100644
> > --- a/drivers/cxl/mem.h
> > +++ b/drivers/cxl/mem.h
> > @@ -3,6 +3,8 @@
> >  #ifndef __CXL_MEM_H__
> >  #define __CXL_MEM_H__
> >  
> > +#include <linux/cdev.h>
> 
> Unrelated?
> 
> > +
> >  /* CXL 2.0 8.2.8.5.1.1 Memory Device Status Register */
> >  #define CXLMDEV_STATUS_OFFSET 0x0
> >  #define   CXLMDEV_DEV_FATAL BIT(0)
> > @@ -46,6 +48,23 @@ struct cxl_memdev {
> >  	int id;
> >  };
> >  
> > +/**
> > + * struct cxl_region - CXL region
> > + * @dev: This region's device.
> > + * @id: This regions id. Id is globally unique across all regions.
> > + * @res: Address space consumed by this region.
> > + * @list: Node in decoders region list.
> > + * @targets: The memory devices comprising the region.
> > + */
> > +struct cxl_region {
> > +	struct device dev;
> > +	int id;
> > +	struct resource res;
> > +	struct list_head list;
> > +	struct cxl_memdev *targets[];
> > +};
> > +
> > +
> 
> One line only.
> 
> >  /**
> >   * struct cxl_mem - A CXL memory device
> >   * @pdev: The PCI device associated with this CXL device.
> > diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
> > new file mode 100644
> > index 000000000000..1f47bc17bd50
> > --- /dev/null
> > +++ b/drivers/cxl/region.c
> > @@ -0,0 +1,155 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/* Copyright(c) 2021 Intel Corporation. All rights reserved. */
> > +#include <linux/io-64-nonatomic-lo-hi.h>
> > +#include <linux/device.h>
> > +#include <linux/module.h>
> > +#include <linux/slab.h>
> > +#include <linux/idr.h>
> > +#include "cxl.h"
> > +#include "mem.h"
> > +
> > +/**
> > + * DOC: cxl region
> > + *
> > + * A CXL region encompasses a chunk of host physical address space that may be
> > + * consumed by a single device (x1 interleave aka linear) or across multiple
> > + * devices (xN interleaved). A region is a child device of a &struct
> > + * cxl_decoder. There may be multiple active regions under a single &struct
> > + * cxl_decoder. The common case for multiple regions would be several linear,
> > + * contiguous regions under a single decoder. Generally, there will be a 1:1
> > + * relationship between decoder and region when the region is interleaved.
> > + */
> > +
> > +static void cxl_region_release(struct device *dev);
> > +
> > +static const struct device_type cxl_region_type = {
> > +	.name = "cxl_region",
> > +	.release = cxl_region_release,
> > +};
> > +
> > +static struct cxl_region *to_cxl_region(struct device *dev)
> > +{
> > +	if (dev_WARN_ONCE(dev, dev->type != &cxl_region_type,
> > +			  "not a cxl_region device\n"))
> > +		return NULL;
> > +
> > +	return container_of(dev, struct cxl_region, dev);
> > +}
> > +
> > +void cxl_free_region(struct cxl_decoder *cxld, struct cxl_region *region)
> > +{
> > +	ida_free(&cxld->region_ida, region->id);
> > +	kfree(region->targets);
> > +	kfree(region);
> > +}
> > +
> > +static void cxl_region_release(struct device *dev)
> > +{
> > +	struct cxl_decoder *cxld = to_cxl_decoder(dev->parent);
> > +	struct cxl_region *region;
> 	struct cxl_region *region = to_cxl_region(dev);
> ?
> Or just roll it into one line.
> 
> cxl_free_region(to_cxl_decoder(dev->parent), to_cxl_region(dev));
> 
> Of course may be affected by later patches so this doesn't make sense
> but I'm too lazy to check!
> 
> > +
> > +	region = to_cxl_region(dev);
> > +	cxl_free_region(cxld, region);
> > +}
> > +
> > +struct cxl_region *cxl_alloc_region(struct cxl_decoder *cxld)
> > +{
> > +	struct cxl_region *region;
> > +	int rc;
> > +
> > +	region = kzalloc(struct_size(region, targets, cxld->interleave_ways),
> > +			 GFP_KERNEL);
> > +	if (!region) {
> > +		pr_err("No memory\n");
> 
> Drop, or move to dev_err? 
> 
> > +		return ERR_PTR(-ENOMEM);
> > +	}
> > +
> > +	rc = ida_alloc(&cxld->region_ida, GFP_KERNEL);
> > +	if (rc < 0) {
> > +		dev_err(&cxld->dev, "Couldn't get a new id\n");
> > +		kfree(region);
> > +		return ERR_PTR(rc);
> > +	}
> > +	region->id = rc;
> > +
> > +	return region;
> > +}
> > +
> > +/**
> > + * cxl_add_region - Adds a region to a decoder
> > + * @cxld: Parent decoder.
> > + * @region: Region to be added to the decoder.
> > + *
> > + * This is the second step of region initialization. Regions exist within an
> > + * address space which is mapped by a @cxld, and that @cxld enforces constraints
> > + * upon the region as it is configured. Regions may be added to a @cxld but not
> > + * activated and therefore it is possible to have more regions in a @cxld than
> > + * there are interleave ways in the @cxld. Regions exist only for persistent
> > + * capacities.
> > + *
> > + * Return: zero if the region was added to the @cxld, else returns negative
> > + * error code.
> > + */
> > +int cxl_add_region(struct cxl_decoder *cxld, struct cxl_region *region)
> > +{
> > +	struct cxl_port *port = to_cxl_port(cxld->dev.parent);
> > +	struct device *dev = &region->dev;
> > +	struct resource *res;
> > +	int rc;
> > +
> > +	device_initialize(dev);
> > +	dev->parent = &cxld->dev;
> > +	dev->bus = &cxl_bus_type;
> > +	dev->type = &cxl_region_type;
> 
> Probably doesn't want the pm controls.
> 
> > +	rc = dev_set_name(dev, "region%d.%d:%d", port->id, cxld->id, region->id);
> > +	if (rc)
> > +		goto err;
> > +
> > +	rc = device_add(dev);
> > +	if (rc)
> > +		goto err;
> > +
> > +	res = &region->res;
> > +	res->name = "Persistent Memory";
> > +	res->start = 0;
> > +	res->end = -1;
> > +	res->flags = IORESOURCE_MEM;
> > +	res->desc = IORES_DESC_PERSISTENT_MEMORY;
> > +
> > +	dev_dbg(dev, "Added %s to %s\n", dev_name(dev), dev_name(&cxld->dev));
> > +
> > +	return 0;
> > +
> > +err:
> > +	put_device(dev);
> > +	return rc;
> > +}
> > +
> > +static struct cxl_region *
> > +cxl_find_region_by_name(struct cxl_decoder *cxld, const char *name)
> > +{
> > +	struct device *region_dev;
> > +
> > +	region_dev = device_find_child_by_name(&cxld->dev, name);
> > +	if (!region_dev)
> > +		return ERR_PTR(-ENOENT);
> > +
> > +	return to_cxl_region(region_dev);
> > +}
> > +
> > +int cxl_delete_region(struct cxl_decoder *cxld, const char *region_name)
> > +{
> > +	struct cxl_region *region;
> > +
> > +	region = cxl_find_region_by_name(cxld, region_name);
> > +	if (IS_ERR(region))
> > +		return PTR_ERR(region);
> > +
> > +	dev_dbg(&cxld->dev, "Requested removal of %s from %s\n",
> > +		dev_name(&region->dev), dev_name(&cxld->dev));
> > +
> > +	device_unregister(&region->dev);
> > +	put_device(&region->dev);
> > +
> > +	return 0;
> > +}
>