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Date:   Fri, 11 Jun 2021 13:57:15 +0100
From:   Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To:     Dan Williams <dan.j.williams@intel.com>
CC:     <linux-cxl@vger.kernel.org>, <nvdimm@lists.linux.dev>,
        <ben.widawsky@intel.com>, <alison.schofield@intel.com>,
        <vishal.l.verma@intel.com>, <ira.weiny@intel.com>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 5/5] cxl/pmem: Register 'pmem' / cxl_nvdimm  devices
Message-ID: <20210611135715.00005da1@Huawei.com>
In-Reply-To: <162336398605.2462439.17422037666825492593.stgit@dwillia2-desk3.amr.corp.intel.com>
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        <162336398605.2462439.17422037666825492593.stgit@dwillia2-desk3.amr.corp.intel.com>
Organization: Huawei Technologies Research and Development (UK) Ltd.
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On Thu, 10 Jun 2021 15:26:26 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> While a memX device on /sys/bus/cxl represents a CXL memory expander
> control interface, a pmemX device represents the persistent memory
> sub-functionality. It bridges the CXL subystem to the libnvdimm nmemX
> control interface.
> 
> With this skeleton ndctl can now see persistent memory devices on a
> "CXL" bus. Later patches add support for translating libnvdimm native
> commands to CXL commands.
> 
> # ndctl list -BDiu -b CXL
> {
>   "provider":"CXL",
>   "dev":"ndbus1",
>   "dimms":[
>     {
>       "dev":"nmem1",
>       "state":"disabled"
>     },
>     {
>       "dev":"nmem0",
>       "state":"disabled"
>     }
>   ]
> }
> 
> Given nvdimm_bus_unregister() removes all devices on an ndbus0 the
> cxl_pmem infrastructure needs to arrange ->remove() to be triggered on
> cxl_nvdimm devices to keep their enabled state synchronized with the
> registration state of their corresponding device on the nvdimm_bus. In
> other words, always arrange for cxl_nvdimm_driver.remove() to unregister
> nvdimms from an nvdimm_bus ahead of the bus being unregistered.
> 
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Being my usual fussy self, I've highlighed a few header changes that
as far as I can see are unrelated to this specific patch.

Otherwise, one request for a local variable name change and
a bit of trivial editorial stuff.

Thanks,

Jonathan


> ---
>  drivers/cxl/core.c |   86 ++++++++++++++++++++++++++++++++++++++++
>  drivers/cxl/cxl.h  |   13 ++++++
>  drivers/cxl/mem.h  |    2 +
>  drivers/cxl/pci.c  |   23 ++++++++---
>  drivers/cxl/pmem.c |  111 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  5 files changed, 217 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/cxl/core.c b/drivers/cxl/core.c
> index f0305c9c91c8..6db660249cea 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"
>  
>  /**
>   * DOC: cxl core
> @@ -731,6 +732,89 @@ struct cxl_nvdimm_bridge *devm_cxl_add_nvdimm_bridge(struct device *host,
>  }
>  EXPORT_SYMBOL_GPL(devm_cxl_add_nvdimm_bridge);
>  
> +static void cxl_nvdimm_release(struct device *dev)
> +{
> +	struct cxl_nvdimm *cxl_nvd = to_cxl_nvdimm(dev);
> +
> +	kfree(cxl_nvd);
> +}
> +
> +static const struct attribute_group *cxl_nvdimm_attribute_groups[] = {
> +	&cxl_base_attribute_group,
> +	NULL,
> +};
> +
> +static const struct device_type cxl_nvdimm_type = {
> +	.name = "cxl_nvdimm",
> +	.release = cxl_nvdimm_release,
> +	.groups = cxl_nvdimm_attribute_groups,
> +};
> +
> +bool is_cxl_nvdimm(struct device *dev)
> +{
> +	return dev->type == &cxl_nvdimm_type;
> +}
> +EXPORT_SYMBOL_GPL(is_cxl_nvdimm);
> +
> +struct cxl_nvdimm *to_cxl_nvdimm(struct device *dev)
> +{
> +	if (dev_WARN_ONCE(dev, !is_cxl_nvdimm(dev),
> +			  "not a cxl_nvdimm device\n"))
> +		return NULL;
> +	return container_of(dev, struct cxl_nvdimm, dev);
> +}
> +EXPORT_SYMBOL_GPL(to_cxl_nvdimm);
> +
> +static struct cxl_nvdimm *cxl_nvdimm_alloc(struct cxl_memdev *cxlmd)
> +{
> +	struct cxl_nvdimm *cxl_nvd;
> +	struct device *dev;
> +
> +	cxl_nvd = kzalloc(sizeof(*cxl_nvd), GFP_KERNEL);
> +	if (!cxl_nvd)
> +		return ERR_PTR(-ENOMEM);
> +
> +	dev = &cxl_nvd->dev;
> +	cxl_nvd->cxlmd = cxlmd;
> +	device_initialize(dev);
> +	device_set_pm_not_required(dev);
> +	dev->parent = &cxlmd->dev;
> +	dev->bus = &cxl_bus_type;
> +	dev->type = &cxl_nvdimm_type;
> +
> +	return cxl_nvd;
> +}
> +
> +int devm_cxl_add_nvdimm(struct device *host, struct cxl_memdev *cxlmd)
> +{
> +	struct cxl_nvdimm *cxl_nvd;
> +	struct device *dev;
> +	int rc;
> +
> +	cxl_nvd = cxl_nvdimm_alloc(cxlmd);
> +	if (IS_ERR(cxl_nvd))
> +		return PTR_ERR(cxl_nvd);
> +
> +	dev = &cxl_nvd->dev;
> +	rc = dev_set_name(dev, "pmem%d", cxlmd->id);
> +	if (rc)
> +		goto err;
> +
> +	rc = device_add(dev);
> +	if (rc)
> +		goto err;
> +
> +	dev_dbg(host, "%s: register %s\n", dev_name(dev->parent),
> +		dev_name(dev));
> +
> +	return devm_add_action_or_reset(host, unregister_dev, dev);
> +
> +err:
> +	put_device(dev);
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(devm_cxl_add_nvdimm);
> +
>  /**
>   * cxl_probe_device_regs() - Detect CXL Device register blocks
>   * @dev: Host device of the @base mapping
> @@ -930,6 +1014,8 @@ static int cxl_device_id(struct device *dev)
>  {
>  	if (dev->type == &cxl_nvdimm_bridge_type)
>  		return CXL_DEVICE_NVDIMM_BRIDGE;
> +	if (dev->type == &cxl_nvdimm_type)
> +		return CXL_DEVICE_NVDIMM;
>  	return 0;
>  }
>  
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 47fcb7ad5978..3f9a6f7b05db 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -213,6 +213,13 @@ struct cxl_nvdimm_bridge {
>  	enum cxl_nvdimm_brige_state state;
>  };
>  
> +struct cxl_mem;

Above looks unrelated as you've not added any uses of cxl_mem

> +struct cxl_nvdimm {
> +	struct device dev;
> +	struct cxl_memdev *cxlmd;
> +	struct nvdimm *nvdimm;
> +};
> +
>  /**
>   * struct cxl_port - logical collection of upstream port devices and
>   *		     downstream port devices to construct a CXL memory
> @@ -299,7 +306,8 @@ int __cxl_driver_register(struct cxl_driver *cxl_drv, struct module *owner,
>  #define cxl_driver_register(x) __cxl_driver_register(x, THIS_MODULE, KBUILD_MODNAME)
>  void cxl_driver_unregister(struct cxl_driver *cxl_drv);
>  
> -#define CXL_DEVICE_NVDIMM_BRIDGE 1
> +#define CXL_DEVICE_NVDIMM_BRIDGE	1
> +#define CXL_DEVICE_NVDIMM		2
>  
>  #define MODULE_ALIAS_CXL(type) MODULE_ALIAS("cxl:t" __stringify(type) "*")
>  #define CXL_MODALIAS_FMT "cxl:t%d"
> @@ -307,4 +315,7 @@ void cxl_driver_unregister(struct cxl_driver *cxl_drv);
>  struct cxl_nvdimm_bridge *to_cxl_nvdimm_bridge(struct device *dev);
>  struct cxl_nvdimm_bridge *devm_cxl_add_nvdimm_bridge(struct device *host,
>  						     struct cxl_port *port);
> +struct cxl_nvdimm *to_cxl_nvdimm(struct device *dev);
> +bool is_cxl_nvdimm(struct device *dev);
> +int devm_cxl_add_nvdimm(struct device *host, struct cxl_memdev *cxlmd);
>  #endif /* __CXL_H__ */
> diff --git a/drivers/cxl/mem.h b/drivers/cxl/mem.h
> index 13868ff7cadf..8f02d02b26b4 100644
> --- a/drivers/cxl/mem.h
> +++ b/drivers/cxl/mem.h
> @@ -2,6 +2,8 @@
>  /* Copyright(c) 2020-2021 Intel Corporation. */
>  #ifndef __CXL_MEM_H__
>  #define __CXL_MEM_H__
> +#include <linux/cdev.h>

Unrelated to rest of patch.  Good to add this, but not hidden in this
patch.

> +#include "cxl.h"
>  
>  /* CXL 2.0 8.2.8.5.1.1 Memory Device Status Register */
>  #define CXLMDEV_STATUS_OFFSET 0x0
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 5a1705b52278..83e81b44c8f5 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -1313,7 +1313,8 @@ static struct cxl_memdev *cxl_memdev_alloc(struct cxl_mem *cxlm)
>  	return ERR_PTR(rc);
>  }
>  
> -static int cxl_mem_add_memdev(struct cxl_mem *cxlm)
> +static struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
> +					      struct cxl_mem *cxlm)
>  {
>  	struct cxl_memdev *cxlmd;
>  	struct device *dev;
> @@ -1322,7 +1323,7 @@ static int cxl_mem_add_memdev(struct cxl_mem *cxlm)
>  
>  	cxlmd = cxl_memdev_alloc(cxlm);
>  	if (IS_ERR(cxlmd))
> -		return PTR_ERR(cxlmd);
> +		return cxlmd;
>  
>  	dev = &cxlmd->dev;
>  	rc = dev_set_name(dev, "mem%d", cxlmd->id);
> @@ -1340,8 +1341,10 @@ static int cxl_mem_add_memdev(struct cxl_mem *cxlm)
>  	if (rc)
>  		goto err;
>  
> -	return devm_add_action_or_reset(dev->parent, cxl_memdev_unregister,
> -					cxlmd);
> +	rc = devm_add_action_or_reset(host, cxl_memdev_unregister, cxlmd);
> +	if (rc)
> +		return ERR_PTR(rc);
> +	return cxlmd;
>  
>  err:
>  	/*
> @@ -1350,7 +1353,7 @@ static int cxl_mem_add_memdev(struct cxl_mem *cxlm)
>  	 */
>  	cxl_memdev_shutdown(cxlmd);
>  	put_device(dev);
> -	return rc;
> +	return ERR_PTR(rc);
>  }
>  
>  static int cxl_xfer_log(struct cxl_mem *cxlm, uuid_t *uuid, u32 size, u8 *out)
> @@ -1561,6 +1564,7 @@ static int cxl_mem_identify(struct cxl_mem *cxlm)
>  
>  static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  {
> +	struct cxl_memdev *cxlmd;
>  	struct cxl_mem *cxlm;
>  	int rc;
>  
> @@ -1588,7 +1592,14 @@ static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	if (rc)
>  		return rc;
>  
> -	return cxl_mem_add_memdev(cxlm);
> +	cxlmd = devm_cxl_add_memdev(&pdev->dev, cxlm);
> +	if (IS_ERR(cxlmd))
> +		return PTR_ERR(cxlmd);
> +
> +	if (range_len(&cxlm->pmem_range) && IS_ENABLED(CONFIG_CXL_PMEM))
> +		rc = devm_cxl_add_nvdimm(&pdev->dev, cxlmd);
> +
> +	return rc;
>  }
>  
>  static const struct pci_device_id cxl_mem_pci_tbl[] = {
> diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
> index 0067bd734559..1ed19e213157 100644
> --- a/drivers/cxl/pmem.c
> +++ b/drivers/cxl/pmem.c
> @@ -3,7 +3,10 @@
>  #include <linux/libnvdimm.h>
>  #include <linux/device.h>
>  #include <linux/module.h>
> +#include <linux/ndctl.h>
> +#include <linux/async.h>
>  #include <linux/slab.h>
> +#include "mem.h"
>  #include "cxl.h"
>  
>  /*
> @@ -13,6 +16,64 @@
>   */
>  static struct workqueue_struct *cxl_pmem_wq;
>  
> +static void unregister_nvdimm(void *nvdimm)
> +{
> +	nvdimm_delete(nvdimm);
> +}
> +
> +static int match_nvdimm_bridge(struct device *dev, const void *data)
> +{
> +	return strcmp(dev_name(dev), "nvdimm-bridge") == 0;
> +}
> +
> +static struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(void)
> +{
> +	struct device *dev;
> +
> +	dev = bus_find_device(&cxl_bus_type, NULL, NULL, match_nvdimm_bridge);

Hmm. It's a singleton, so you could just stash the pointer somewhere
appropriate, but I guess this avoids adding extra infrastructure around
that, so fair enough.

> +	if (!dev)
> +		return NULL;
> +	return to_cxl_nvdimm_bridge(dev);
> +}
> +
> +static int cxl_nvdimm_probe(struct device *dev)
> +{
> +	struct cxl_nvdimm *cxl_nvd = to_cxl_nvdimm(dev);
> +	struct cxl_nvdimm_bridge *cxl_nvb;
> +	unsigned long flags = 0;
> +	struct nvdimm *nvdimm;
> +	int rc = -ENXIO;
> +
> +	cxl_nvb = cxl_find_nvdimm_bridge();
> +	if (!cxl_nvb)
> +		return -ENXIO;
> +
> +	device_lock(&cxl_nvb->dev);
> +	if (!cxl_nvb->nvdimm_bus)
> +		goto out;
> +
> +	set_bit(NDD_LABELING, &flags);
> +	nvdimm = nvdimm_create(cxl_nvb->nvdimm_bus, cxl_nvd, NULL, flags, 0, 0,
> +			       NULL);
> +	if (!nvdimm)
> +		goto out;
> +
> +	dev_set_drvdata(dev, nvdimm);

Why?  No harm done, but I wanted to check this was only used to get the
nvdimm, but can't find where it's used at all.

> +
> +	rc = devm_add_action_or_reset(dev, unregister_nvdimm, nvdimm);
> +out:
> +	device_unlock(&cxl_nvb->dev);
> +	put_device(&cxl_nvb->dev);
> +
> +	return rc;
> +}
> +
> +static struct cxl_driver cxl_nvdimm_driver = {
> +	.name = "cxl_nvdimm",
> +	.probe = cxl_nvdimm_probe,
> +	.id = CXL_DEVICE_NVDIMM,
> +};
> +
>  static int cxl_pmem_ctl(struct nvdimm_bus_descriptor *nd_desc,
>  			struct nvdimm *nvdimm, unsigned int cmd, void *buf,
>  			unsigned int buf_len, int *cmd_rc)
> @@ -28,19 +89,31 @@ static void online_nvdimm_bus(struct cxl_nvdimm_bridge *cxl_nvb)
>  		nvdimm_bus_register(&cxl_nvb->dev, &cxl_nvb->nd_desc);
>  }
>  
> -static void offline_nvdimm_bus(struct cxl_nvdimm_bridge *cxl_nvb)
> +static int cxl_nvdimm_release_driver(struct device *dev, void *data)
>  {
> -	if (!cxl_nvb->nvdimm_bus)
> -		return;
> -	nvdimm_bus_unregister(cxl_nvb->nvdimm_bus);
> -	cxl_nvb->nvdimm_bus = NULL;
> +	if (!is_cxl_nvdimm(dev))
> +		return 0;
> +	device_release_driver(dev);
> +	return 0;
> +}
> +
> +static void offline_nvdimm_bus(struct nvdimm_bus *nvdimm_bus)
> +{
> +	/*
> +	 * Set the state of cxl_nvdimm devices to unbound / idle before
> +	 * nvdimm_bus_unregister() rips the nvdimm objects out from
> +	 * underneath them.
> +	 */
> +	bus_for_each_dev(&cxl_bus_type, NULL, NULL, cxl_nvdimm_release_driver);
> +	nvdimm_bus_unregister(nvdimm_bus);
>  }
>  
>  static void cxl_nvb_update_state(struct work_struct *work)
>  {
>  	struct cxl_nvdimm_bridge *cxl_nvb =
>  		container_of(work, typeof(*cxl_nvb), state_work);
> -	bool release = false;
> +	struct nvdimm_bus *nvdimm_bus = NULL;
> +	bool release = false, rescan = false;
>  
>  	device_lock(&cxl_nvb->dev);
>  	switch (cxl_nvb->state) {
> @@ -50,11 +123,13 @@ static void cxl_nvb_update_state(struct work_struct *work)
>  			dev_err(&cxl_nvb->dev,
>  				"failed to establish nvdimm bus\n");
>  			release = true;
> -		}
> +		} else
> +			rescan = true;
>  		break;
>  	case CXL_NVB_OFFLINE:
>  	case CXL_NVB_DEAD:
> -		offline_nvdimm_bus(cxl_nvb);
> +		nvdimm_bus = cxl_nvb->nvdimm_bus;

Perhaps rename this to make it clear that it only exists as a means
to offline it later?  I wondered briefly why you were offlining
any bus that existed (e.g. in the online case)

nvdimm_bus_to_offline = ...

> +		cxl_nvb->nvdimm_bus = NULL;
>  		break;
>  	default:
>  		break;
> @@ -63,6 +138,13 @@ static void cxl_nvb_update_state(struct work_struct *work)
>  
>  	if (release)
>  		device_release_driver(&cxl_nvb->dev);
> +	if (rescan) {
> +		int rc = bus_rescan_devices(&cxl_bus_type);
> +
> +		dev_dbg(&cxl_nvb->dev, "rescan: %d\n", rc);
> +	}
> +	if (nvdimm_bus)
> +		offline_nvdimm_bus(nvdimm_bus);
>  
>  	put_device(&cxl_nvb->dev);
>  }
> @@ -113,23 +195,29 @@ static __init int cxl_pmem_init(void)
>  	int rc;
>  
>  	cxl_pmem_wq = alloc_ordered_workqueue("cxl_pmem", 0);
> -

Shouldn't be here obviously. Move to earlier patch.

>  	if (!cxl_pmem_wq)
>  		return -ENXIO;
>  
>  	rc = cxl_driver_register(&cxl_nvdimm_bridge_driver);
>  	if (rc)
> -		goto err;
> +		goto err_bridge;
> +
> +	rc = cxl_driver_register(&cxl_nvdimm_driver);
> +	if (rc)
> +		goto err_nvdimm;
>  
>  	return 0;
>  
> -err:
> +err_nvdimm:
> +	cxl_driver_unregister(&cxl_nvdimm_bridge_driver);
> +err_bridge:
>  	destroy_workqueue(cxl_pmem_wq);
>  	return rc;
>  }
>  
>  static __exit void cxl_pmem_exit(void)
>  {
> +	cxl_driver_unregister(&cxl_nvdimm_driver);
>  	cxl_driver_unregister(&cxl_nvdimm_bridge_driver);
>  	destroy_workqueue(cxl_pmem_wq);
>  }
> @@ -139,3 +227,4 @@ module_init(cxl_pmem_init);
>  module_exit(cxl_pmem_exit);
>  MODULE_IMPORT_NS(CXL);
>  MODULE_ALIAS_CXL(CXL_DEVICE_NVDIMM_BRIDGE);
> +MODULE_ALIAS_CXL(CXL_DEVICE_NVDIMM);
>