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Subject: Re: [PATCH v3 10/27] powerpc: Add driver for OpenCAPI Persistent
 Memory
From:   "Alastair D'Silva" <alastair@au1.ibm.com>
To:     Frederic Barrat <fbarrat@linux.ibm.com>
Cc:     "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        "Oliver O'Halloran" <oohall@gmail.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Andrew Donnellan <ajd@linux.ibm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Rob Herring <robh@kernel.org>,
        Anton Blanchard <anton@ozlabs.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@linux.vnet.ibm.com>,
        =?ISO-8859-1?Q?C=E9dric?= Le Goater <clg@kaod.org>,
        Anju T Sudhakar <anju@linux.vnet.ibm.com>,
        Hari Bathini <hbathini@linux.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kurz <groug@kaod.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-nvdimm@lists.01.org, linux-mm@kvack.org
Date:   Fri, 28 Feb 2020 11:54:52 +1100
In-Reply-To: <da02a596-ce4e-f004-5072-cb3dff0a7484@linux.ibm.com>
References: <20200221032720.33893-1-alastair@au1.ibm.com>
         <20200221032720.33893-11-alastair@au1.ibm.com>
         <da02a596-ce4e-f004-5072-cb3dff0a7484@linux.ibm.com>
Organization: IBM Australia
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On Thu, 2020-02-27 at 21:44 +0100, Frederic Barrat wrote:
> 
> Le 21/02/2020 à 04:27, Alastair D'Silva a écrit :
> > From: Alastair D'Silva <alastair@d-silva.org>
> > 
> > This driver exposes LPC memory on OpenCAPI pmem cards
> > as an NVDIMM, allowing the existing nvram infrastructure
> > to be used.
> > 
> > Namespace metadata is stored on the media itself, so
> > scm_reserve_metadata() maps 1 section's worth of PMEM storage
> > at the start to hold this. The rest of the PMEM range is registered
> > with libnvdimm as an nvdimm. scm_ndctl_config_read/write/size()
> > provide
> > callbacks to libnvdimm to access the metadata.
> > 
> > Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
> > ---
> >   arch/powerpc/platforms/powernv/Kconfig        |   3 +
> >   arch/powerpc/platforms/powernv/Makefile       |   1 +
> >   arch/powerpc/platforms/powernv/pmem/Kconfig   |  15 +
> >   arch/powerpc/platforms/powernv/pmem/Makefile  |   7 +
> >   arch/powerpc/platforms/powernv/pmem/ocxl.c    | 473
> > ++++++++++++++++++
> >   .../platforms/powernv/pmem/ocxl_internal.h    |  28 ++
> >   6 files changed, 527 insertions(+)
> >   create mode 100644 arch/powerpc/platforms/powernv/pmem/Kconfig
> >   create mode 100644 arch/powerpc/platforms/powernv/pmem/Makefile
> >   create mode 100644 arch/powerpc/platforms/powernv/pmem/ocxl.c
> >   create mode 100644
> > arch/powerpc/platforms/powernv/pmem/ocxl_internal.h
> > 
> > diff --git a/arch/powerpc/platforms/powernv/Kconfig
> > b/arch/powerpc/platforms/powernv/Kconfig
> > index 938803eab0ad..fc8976af0e52 100644
> > --- a/arch/powerpc/platforms/powernv/Kconfig
> > +++ b/arch/powerpc/platforms/powernv/Kconfig
> > @@ -50,3 +50,6 @@ config PPC_VAS
> >   config SCOM_DEBUGFS
> >   	bool "Expose SCOM controllers via debugfs"
> >   	depends on DEBUG_FS
> > +
> > +source "arch/powerpc/platforms/powernv/pmem/Kconfig"
> > +
> > diff --git a/arch/powerpc/platforms/powernv/Makefile
> > b/arch/powerpc/platforms/powernv/Makefile
> > index c0f8120045c3..0bbd72988b6f 100644
> > --- a/arch/powerpc/platforms/powernv/Makefile
> > +++ b/arch/powerpc/platforms/powernv/Makefile
> > @@ -21,3 +21,4 @@ obj-$(CONFIG_PPC_VAS)	+= vas.o vas-window.o
> > vas-debug.o
> >   obj-$(CONFIG_OCXL_BASE)	+= ocxl.o
> >   obj-$(CONFIG_SCOM_DEBUGFS) += opal-xscom.o
> >   obj-$(CONFIG_PPC_SECURE_BOOT) += opal-secvar.o
> > +obj-$(CONFIG_LIBNVDIMM) += pmem/
> > diff --git a/arch/powerpc/platforms/powernv/pmem/Kconfig
> > b/arch/powerpc/platforms/powernv/pmem/Kconfig
> > new file mode 100644
> > index 000000000000..c5d927520920
> > --- /dev/null
> > +++ b/arch/powerpc/platforms/powernv/pmem/Kconfig
> > @@ -0,0 +1,15 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +if LIBNVDIMM
> > +
> > +config OCXL_PMEM
> > +	tristate "OpenCAPI Persistent Memory"
> > +	depends on LIBNVDIMM && PPC_POWERNV && PCI && EEH &&
> > ZONE_DEVICE && OCXL
> > +	help
> > +	  Exposes devices that implement the OpenCAPI Storage Class
> > Memory
> > +	  specification as persistent memory regions. You may also want
> > +	  DEV_DAX, DEV_DAX_PMEM & FS_DAX if you plan on using DAX
> > devices
> > +	  stacked on top of this driver.
> > +
> > +	  Select N if unsure.
> > +
> > +endif
> > diff --git a/arch/powerpc/platforms/powernv/pmem/Makefile
> > b/arch/powerpc/platforms/powernv/pmem/Makefile
> > new file mode 100644
> > index 000000000000..1c55c4193175
> > --- /dev/null
> > +++ b/arch/powerpc/platforms/powernv/pmem/Makefile
> > @@ -0,0 +1,7 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +ccflags-$(CONFIG_PPC_WERROR)	+= -Werror
> > +
> > +obj-$(CONFIG_OCXL_PMEM) += ocxlpmem.o
> > +
> > +ocxlpmem-y := ocxl.o
> > diff --git a/arch/powerpc/platforms/powernv/pmem/ocxl.c
> > b/arch/powerpc/platforms/powernv/pmem/ocxl.c
> > new file mode 100644
> > index 000000000000..3c4eeb5dcc0f
> > --- /dev/null
> > +++ b/arch/powerpc/platforms/powernv/pmem/ocxl.c
> > @@ -0,0 +1,473 @@
> > +// SPDX-License-Id
> > +// Copyright 2019 IBM Corp.
> > +
> > +/*
> > + * A driver for OpenCAPI devices that implement the Storage Class
> > + * Memory specification.
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <misc/ocxl.h>
> > +#include <linux/ndctl.h>
> > +#include <linux/mm_types.h>
> > +#include <linux/memory_hotplug.h>
> > +#include "ocxl_internal.h"
> > +
> > +
> > +static const struct pci_device_id ocxlpmem_pci_tbl[] = {
> > +	{ PCI_DEVICE(PCI_VENDOR_ID_IBM, 0x0625), },
> > +	{ }
> > +};
> > +
> > +MODULE_DEVICE_TABLE(pci, ocxlpmem_pci_tbl);
> > +
> > +#define NUM_MINORS 256 // Total to reserve
> > +
> > +static dev_t ocxlpmem_dev;
> > +static struct class *ocxlpmem_class;
> > +static struct mutex minors_idr_lock;
> > +static struct idr minors_idr;
> > +
> > +/**
> > + * ndctl_config_write() - Handle a ND_CMD_SET_CONFIG_DATA command
> > from ndctl
> > + * @ocxlpmem: the device metadata
> > + * @command: the incoming data to write
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int ndctl_config_write(struct ocxlpmem *ocxlpmem,
> > +			      struct nd_cmd_set_config_hdr *command)
> > +{
> > +	if (command->in_offset + command->in_length > LABEL_AREA_SIZE)
> > +		return -EINVAL;
> > +
> > +	memcpy_flushcache(ocxlpmem->metadata_addr + command->in_offset, 
> > command->in_buf,
> > +			  command->in_length);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * ndctl_config_read() - Handle a ND_CMD_GET_CONFIG_DATA command
> > from ndctl
> > + * @ocxlpmem: the device metadata
> > + * @command: the read request
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int ndctl_config_read(struct ocxlpmem *ocxlpmem,
> > +			     struct nd_cmd_get_config_data_hdr
> > *command)
> > +{
> > +	if (command->in_offset + command->in_length > LABEL_AREA_SIZE)
> > +		return -EINVAL;
> > +
> > +	memcpy_mcsafe(command->out_buf, ocxlpmem->metadata_addr +
> > command->in_offset,
> > +		      command->in_length);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * ndctl_config_size() - Handle a ND_CMD_GET_CONFIG_SIZE command
> > from ndctl
> > + * @command: the read request
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int ndctl_config_size(struct nd_cmd_get_config_size
> > *command)
> > +{
> > +	command->status = 0;
> > +	command->config_size = LABEL_AREA_SIZE;
> > +	command->max_xfer = PAGE_SIZE;
> > +
> > +	return 0;
> > +}
> > +
> > +static int ndctl(struct nvdimm_bus_descriptor *nd_desc,
> > +		 struct nvdimm *nvdimm,
> > +		 unsigned int cmd, void *buf, unsigned int buf_len, int
> > *cmd_rc)
> > +{
> > +	struct ocxlpmem *ocxlpmem = container_of(nd_desc, struct
> > ocxlpmem, bus_desc);
> > +
> > +	switch (cmd) {
> > +	case ND_CMD_GET_CONFIG_SIZE:
> > +		*cmd_rc = ndctl_config_size(buf);
> > +		return 0;
> > +
> > +	case ND_CMD_GET_CONFIG_DATA:
> > +		*cmd_rc = ndctl_config_read(ocxlpmem, buf);
> > +		return 0;
> > +
> > +	case ND_CMD_SET_CONFIG_DATA:
> > +		*cmd_rc = ndctl_config_write(ocxlpmem, buf);
> > +		return 0;
> > +
> > +	default:
> > +		return -ENOTTY;
> > +	}
> > +}
> > +
> > +/**
> > + * reserve_metadata() - Reserve space for nvdimm metadata
> > + * @ocxlpmem: the device metadata
> > + * @lpc_mem: The resource representing the LPC memory of the
> > OpenCAPI device
> > + */
> > +static int reserve_metadata(struct ocxlpmem *ocxlpmem,
> > +			    struct resource *lpc_mem)
> > +{
> > +	ocxlpmem->metadata_addr = devm_memremap(&ocxlpmem->dev,
> > lpc_mem->start,
> > +						LABEL_AREA_SIZE,
> > MEMREMAP_WB);
> > +	if (IS_ERR(ocxlpmem->metadata_addr))
> > +		return PTR_ERR(ocxlpmem->metadata_addr);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * register_lpc_mem() - Discover persistent memory on a device and
> > register it with the NVDIMM subsystem
> > + * @ocxlpmem: the device metadata
> > + * Return: 0 on success
> > + */
> > +static int register_lpc_mem(struct ocxlpmem *ocxlpmem)
> > +{
> > +	struct nd_region_desc region_desc;
> > +	struct nd_mapping_desc nd_mapping_desc;
> > +	struct resource *lpc_mem;
> > +	const struct ocxl_afu_config *config;
> > +	const struct ocxl_fn_config *fn_config;
> > +	int rc;
> > +	unsigned long nvdimm_cmd_mask = 0;
> > +	unsigned long nvdimm_flags = 0;
> > +	int target_node;
> > +	char serial[16+1];
> > +
> > +	// Set up the reserved metadata area
> > +	rc = ocxl_afu_map_lpc_mem(ocxlpmem->ocxl_afu);
> > +	if (rc < 0)
> > +		return rc;
> > +
> > +	lpc_mem = ocxl_afu_lpc_mem(ocxlpmem->ocxl_afu);
> > +	if (lpc_mem == NULL || lpc_mem->start == 0)
> > +		return -EINVAL;
> > +
> > +	config = ocxl_afu_config(ocxlpmem->ocxl_afu);
> > +	fn_config = ocxl_function_config(ocxlpmem->ocxl_fn);
> > +
> > +	rc = reserve_metadata(ocxlpmem, lpc_mem);
> > +	if (rc)
> > +		return rc;
> > +
> > +	ocxlpmem->bus_desc.provider_name = "ocxl-pmem";
> > +	ocxlpmem->bus_desc.ndctl = ndctl;
> > +	ocxlpmem->bus_desc.module = THIS_MODULE;
> > +
> > +	ocxlpmem->nvdimm_bus = nvdimm_bus_register(&ocxlpmem->dev,
> > +						   &ocxlpmem-
> > >bus_desc);
> > +	if (!ocxlpmem->nvdimm_bus)
> > +		return -EINVAL;
> > +
> > +	ocxlpmem->pmem_res.start = (u64)lpc_mem->start +
> > LABEL_AREA_SIZE;
> > +	ocxlpmem->pmem_res.end = (u64)lpc_mem->start + config-
> > >lpc_mem_size - 1;
> > +	ocxlpmem->pmem_res.name = "OpenCAPI persistent memory";
> > +
> > +	set_bit(ND_CMD_GET_CONFIG_SIZE, &nvdimm_cmd_mask);
> > +	set_bit(ND_CMD_GET_CONFIG_DATA, &nvdimm_cmd_mask);
> > +	set_bit(ND_CMD_SET_CONFIG_DATA, &nvdimm_cmd_mask);
> > +
> > +	set_bit(NDD_ALIASING, &nvdimm_flags);
> > +
> > +	snprintf(serial, sizeof(serial), "%llx", fn_config->serial);
> > +	nd_mapping_desc.nvdimm = nvdimm_create(ocxlpmem->nvdimm_bus,
> > ocxlpmem,
> > +				 NULL, nvdimm_flags, nvdimm_cmd_mask,
> > +				 0, NULL);
> > +	if (!nd_mapping_desc.nvdimm)
> > +		return -ENOMEM;
> > +
> > +	if (nvdimm_bus_check_dimm_count(ocxlpmem->nvdimm_bus, 1))
> > +		return -EINVAL;
> > +
> > +	nd_mapping_desc.start = ocxlpmem->pmem_res.start;
> > +	nd_mapping_desc.size = resource_size(&ocxlpmem->pmem_res);
> > +	nd_mapping_desc.position = 0;
> > +
> > +	ocxlpmem->nd_set.cookie1 = fn_config->serial + 1; // allow for
> > empty serial
> > +	ocxlpmem->nd_set.cookie2 = fn_config->serial + 1;
> > +
> > +	target_node = of_node_to_nid(ocxlpmem->pdev->dev.of_node);
> > +
> > +	memset(&region_desc, 0, sizeof(region_desc));
> > +	region_desc.res = &ocxlpmem->pmem_res;
> > +	region_desc.numa_node = NUMA_NO_NODE;
> > +	region_desc.target_node = target_node;
> > +	region_desc.num_mappings = 1;
> > +	region_desc.mapping = &nd_mapping_desc;
> > +	region_desc.nd_set = &ocxlpmem->nd_set;
> > +
> > +	set_bit(ND_REGION_PAGEMAP, &region_desc.flags);
> > +	/*
> > +	 * NB: libnvdimm copies the data from ndr_desc into it's own
> > +	 * structures so passing a stack pointer is fine.
> > +	 */
> > +	ocxlpmem->nd_region = nvdimm_pmem_region_create(ocxlpmem-
> > >nvdimm_bus,
> > +							&region_desc);
> > +	if (!ocxlpmem->nd_region)
> > +		return -EINVAL;
> > +
> > +	dev_info(&ocxlpmem->dev,
> > +		 "Onlining %lluMB of persistent memory\n",
> > +		 nd_mapping_desc.size / SZ_1M);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * allocate_minor() - Allocate a minor number to use for an
> > OpenCAPI pmem device
> > + * @ocxlpmem: the device metadata
> > + * Return: the allocated minor number
> > + */
> > +static int allocate_minor(struct ocxlpmem *ocxlpmem)
> > +{
> > +	int minor;
> > +
> > +	mutex_lock(&minors_idr_lock);
> > +	minor = idr_alloc(&minors_idr, ocxlpmem, 0, NUM_MINORS,
> > GFP_KERNEL);
> > +	mutex_unlock(&minors_idr_lock);
> > +	return minor;
> > +}
> > +
> > +static void free_minor(struct ocxlpmem *ocxlpmem)
> > +{
> > +	mutex_lock(&minors_idr_lock);
> > +	idr_remove(&minors_idr, MINOR(ocxlpmem->dev.devt));
> > +	mutex_unlock(&minors_idr_lock);
> > +}
> > +
> > +/**
> > + * free_ocxlpmem() - Free all members of an ocxlpmem struct
> > + * @ocxlpmem: the device struct to clear
> > + */
> > +static void free_ocxlpmem(struct ocxlpmem *ocxlpmem)
> > +{
> > +	int rc;
> > +
> > +	if (ocxlpmem->nvdimm_bus)
> > +		nvdimm_bus_unregister(ocxlpmem->nvdimm_bus);
> > +
> > +	free_minor(ocxlpmem);
> > +
> > +	if (ocxlpmem->metadata_addr)
> > +		devm_memunmap(&ocxlpmem->dev, ocxlpmem->metadata_addr);
> > +
> > +	if (ocxlpmem->ocxl_context) {
> > +		rc = ocxl_context_detach(ocxlpmem->ocxl_context);
> > +		if (rc == -EBUSY)
> > +			dev_warn(&ocxlpmem->dev, "Timeout detaching
> > ocxl context\n");
> > +		else
> > +			ocxl_context_free(ocxlpmem->ocxl_context);
> > +
> > +	}
> > +
> > +	if (ocxlpmem->ocxl_afu)
> > +		ocxl_afu_put(ocxlpmem->ocxl_afu);
> > +
> > +	if (ocxlpmem->ocxl_fn)
> > +		ocxl_function_close(ocxlpmem->ocxl_fn);
> > +
> > +	kfree(ocxlpmem);
> > +}
> > +
> > +/**
> > + * free_ocxlpmem_dev() - Free an OpenCAPI persistent memory device
> > + * @dev: The device struct
> > + */
> > +static void free_ocxlpmem_dev(struct device *dev)
> > +{
> > +	struct ocxlpmem *ocxlpmem = container_of(dev, struct ocxlpmem,
> > dev);
> > +
> > +	free_ocxlpmem(ocxlpmem);
> > +}
> > +
> > +/**
> > + * ocxlpmem_register() - Register an OpenCAPI pmem device with the
> > kernel
> > + * @ocxlpmem: the device metadata
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int ocxlpmem_register(struct ocxlpmem *ocxlpmem)
> > +{
> > +	int rc;
> > +	int minor = allocate_minor(ocxlpmem);
> > +
> > +	if (minor < 0)
> > +		return minor;
> > +
> > +	ocxlpmem->dev.release = free_ocxlpmem_dev;
> > +	rc = dev_set_name(&ocxlpmem->dev, "ocxlpmem%d", minor);
> > +	if (rc < 0)
> > +		return rc;
> > +
> > +	ocxlpmem->dev.devt = MKDEV(MAJOR(ocxlpmem_dev), minor);
> > +	ocxlpmem->dev.class = ocxlpmem_class;
> 
> 
> This function, as well as allocate_minor() and free_minor() above 
> reference resources (the IDR, the file class, ...) which are not 
> initialized yet. The function file_init() is coming in a later patch.
> 

Thanks, I caught this at runtime when I booted a kernel with (just)
this patch :) Fixed in v4.

> 
> 
> > +	ocxlpmem->dev.parent = &ocxlpmem->pdev->dev;
> > +
> > +	return device_register(&ocxlpmem->dev);
> > +}
> > +
> > +/**
> > + * ocxlpmem_remove() - Free an OpenCAPI persistent memory device
> > + * @pdev: the PCI device information struct
> > + */
> > +static void ocxlpmem_remove(struct pci_dev *pdev)
> > +{
> > +	if (PCI_FUNC(pdev->devfn) == 0) {
> > +		struct ocxlpmem_function0 *func0 =
> > pci_get_drvdata(pdev);
> > +
> > +		if (func0) {
> > +			ocxl_function_close(func0->ocxl_fn);
> > +			func0->ocxl_fn = NULL;
> > +		}
> 
> 
> The struct ocxlpmem_function0 allocated on probe() should be freed.
> 

I've dropped struct as per the thread from Andrew Donellan.

> 
> 
> > +	} else {
> > +		struct ocxlpmem *ocxlpmem = pci_get_drvdata(pdev);
> > +
> > +		if (ocxlpmem)
> > +			device_unregister(&ocxlpmem->dev);
> > +	}
> > +}
> > +
> > +/**
> > + * probe_function0() - Set up function 0 for an OpenCAPI
> > persistent memory device
> > + * This is important as it enables templates higher than 0 across
> > all other functions,
> > + * which in turn enables higher bandwidth accesses
> > + * @pdev: the PCI device information struct
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int probe_function0(struct pci_dev *pdev)
> > +{
> > +	struct ocxlpmem_function0 *func0 = NULL;
> > +	struct ocxl_fn *fn;
> > +
> > +	func0 = kzalloc(sizeof(*func0), GFP_KERNEL);
> > +	if (!func0)
> > +		return -ENOMEM;
> > +
> > +	func0->pdev = pdev;
> 
> 
> Storing the struct pci_dev for function 0 appears to be useless.
> 

Yup

> 
> 
> > +	fn = ocxl_function_open(pdev);
> > +	if (IS_ERR(fn)) {
> > +		kfree(func0);
> > +		dev_err(&pdev->dev, "failed to open OCXL function\n");
> > +		return PTR_ERR(fn);
> > +	}
> > +	func0->ocxl_fn = fn;
> > +
> > +	pci_set_drvdata(pdev, func0);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * probe() - Init an OpenCAPI persistent memory device
> > + * @pdev: the PCI device information struct
> > + * @ent: The entry from ocxlpmem_pci_tbl
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int probe(struct pci_dev *pdev, const struct pci_device_id
> > *ent)
> > +{
> > +	struct ocxlpmem *ocxlpmem;
> > +	int rc;
> > +
> > +	if (PCI_FUNC(pdev->devfn) == 0)
> > +		return probe_function0(pdev);
> > +	else if (PCI_FUNC(pdev->devfn) != 1)
> > +		return 0;
> > +
> > +	ocxlpmem = kzalloc(sizeof(*ocxlpmem), GFP_KERNEL);
> > +	if (!ocxlpmem) {
> > +		dev_err(&pdev->dev, "Could not allocate OpenCAPI
> > persistent memory metadata\n");
> > +		rc = -ENOMEM;
> > +		goto err;
> > +	}
> > +	ocxlpmem->pdev = pdev;
> 
> We should probably call pci_dev_get() here if we store the struct 
> pci_dev pointer. We could debate how useful it really is,
> considering 
> we're registering a device, which will also take a reference, but it 
> looks like the safe thing to do considering all those resources
> don't 
> have exactly the same life cycle and it is standard practice to 
> guarantee that we won't have a dangling pointer.
> 

Ok

> 
> 
> > +
> > +	pci_set_drvdata(pdev, ocxlpmem);
> > +
> > +	ocxlpmem->ocxl_fn = ocxl_function_open(pdev);
> > +	if (IS_ERR(ocxlpmem->ocxl_fn)) {
> > +		kfree(ocxlpmem);
> 
> ocxlpmem is freed...
> 
> 
> > +		pci_set_drvdata(pdev, NULL);
> > +		dev_err(&pdev->dev, "failed to open OCXL function\n");
> > +		rc = PTR_ERR(ocxlpmem->ocxl_fn);
> 
> ... and then referenced.
> 

Ok

> 
> 
> > +		goto err;
> > +	}
> > +
> > +	ocxlpmem->ocxl_afu = ocxl_function_fetch_afu(ocxlpmem->ocxl_fn, 
> > 0);
> > +	if (ocxlpmem->ocxl_afu == NULL) {
> > +		dev_err(&pdev->dev, "Could not get OCXL AFU from
> > function\n");
> 
> The error path here should match the above, to free struct ocxlpmem.
> 

Yup, I've factored out err_unregiseterd to unify the error paths.

> 
> > +		rc = -ENXIO;
> > +		goto err;
> > +	}
> > +
> > +	ocxl_afu_get(ocxlpmem->ocxl_afu);
> > +
> > +	// Resources allocated below here are cleaned up in the release
> > handler
> > +
> > +	rc = ocxlpmem_register(ocxlpmem);
> > +	if (rc) {
> > +		dev_err(&pdev->dev, "Could not register OpenCAPI
> > persistent memory device with the kernel\n");
> > +		goto err;
> > +	}
> > +
> > +	rc = ocxl_context_alloc(&ocxlpmem->ocxl_context, ocxlpmem-
> > >ocxl_afu, NULL);
> > +	if (rc) {
> > +		dev_err(&pdev->dev, "Could not allocate OCXL
> > context\n");
> > +		goto err;
> > +	}
> > +
> > +	rc = ocxl_context_attach(ocxlpmem->ocxl_context, 0, NULL);
> > +	if (rc) {
> > +		dev_err(&pdev->dev, "Could not attach ocxl context\n");
> > +		goto err;
> > +	}
> > +
> > +	rc = register_lpc_mem(ocxlpmem);
> > +	if (rc) {
> > +		dev_err(&pdev->dev, "Could not register OpenCAPI
> > persistent memory with libnvdimm\n");
> > +		goto err;
> > +	}
> > +
> > +	return 0;
> > +
> > +err:
> > +	/*
> > +	 * Further cleanup is done in the release handler via
> > free_ocxlpmem()
> > +	 * This allows us to keep the character device live to handle
> > IOCTLs to
> > +	 * investigate issues if the card has an error
> > +	 */
> 
> If we fail probe, we don't call device_unregister() and the data 
> structures will never be freed. The comment seems to indicate it's
> done 
> on purpose but that looks suprising and wrong. If we fail probe, the 
> kernel thinks the driver it _not_ handling the device, so we need to 
> exit probe() cleanly. We're not supposed to be able to make some
> debug 
> ioctl calls. Once we fail probe, the kernel is free to do whatever
> it 
> wants with the pci device. If you manage to extract some debug info 
> during development, then fine, but it's not something we can rely on
> and 
> upstream.
> If the card enters an error state after probe(), then we don't need
> that 
> anyway. We have all the time in the world to call ioctl's, as long as
> we 
> don't call the remove callback of the driver.
> 
> 

Ok

> 
> 
> > +
> > +	dev_err(&pdev->dev,
> > +		"Error detected, will not register OpenCAPI persistent
> > memory\n");
> > +	return rc;
> > +}
> > +
> > +static struct pci_driver pci_driver = {
> > +	.name = "ocxl-pmem",
> > +	.id_table = ocxlpmem_pci_tbl,
> > +	.probe = probe,
> > +	.remove = ocxlpmem_remove,
> > +	.shutdown = ocxlpmem_remove,
> 
> 
> nitpick: why doesn't the probe callback follow the same naming 
> convention? It's all static and doesn't really matter, but...

I had dropped the prefix when I renamed from scm as it doesn't really
value-add, but clearly, I missed some :) I'll fix it.

> 
>    Fred
> 
> 
> 
> > +};
> > +
> > +static int __init ocxlpmem_init(void)
> > +{
> > +	int rc = 0;
> > +
> > +	rc = pci_register_driver(&pci_driver);
> > +	if (rc)
> > +		return rc;
> > +
> > +	return 0;
> > +}
> > +
> > +static void ocxlpmem_exit(void)
> > +{
> > +	pci_unregister_driver(&pci_driver);
> > +}
> > +
> > +module_init(ocxlpmem_init);
> > +module_exit(ocxlpmem_exit);
> > +
> > +MODULE_DESCRIPTION("OpenCAPI Persistent Memory");
> > +MODULE_LICENSE("GPL");
> > diff --git a/arch/powerpc/platforms/powernv/pmem/ocxl_internal.h
> > b/arch/powerpc/platforms/powernv/pmem/ocxl_internal.h
> > new file mode 100644
> > index 000000000000..0faf3740e9b8
> > --- /dev/null
> > +++ b/arch/powerpc/platforms/powernv/pmem/ocxl_internal.h
> > @@ -0,0 +1,28 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +// Copyright 2019 IBM Corp.
> > +
> > +#include <linux/pci.h>
> > +#include <misc/ocxl.h>
> > +#include <linux/libnvdimm.h>
> > +#include <linux/mm.h>
> > +
> > +#define LABEL_AREA_SIZE	(1UL << PA_SECTION_SHIFT)
> > +
> > +struct ocxlpmem_function0 {
> > +	struct pci_dev *pdev;
> > +	struct ocxl_fn *ocxl_fn;
> > +};
> > +
> > +struct ocxlpmem {
> > +	struct device dev;
> > +	struct pci_dev *pdev;
> > +	struct ocxl_fn *ocxl_fn;
> > +	struct nd_interleave_set nd_set;
> > +	struct nvdimm_bus_descriptor bus_desc;
> > +	struct nvdimm_bus *nvdimm_bus;
> > +	struct ocxl_afu *ocxl_afu;
> > +	struct ocxl_context *ocxl_context;
> > +	void *metadata_addr;
> > +	struct resource pmem_res;
> > +	struct nd_region *nd_region;
> > +};
> > 
-- 
Alastair D'Silva
Open Source Developer
Linux Technology Centre, IBM Australia
mob: 0423 762 819