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SubjectRe: [PATCH v3 10/27] powerpc: Add driver for OpenCAPI Persistent Memory
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On Wed, 2020-02-26 at 16:07 +1100, Andrew Donnellan wrote:
> On 21/2/20 2:27 pm, Alastair D'Silva wrote:
> > 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>
>
> I'm not particularly familiar with the nvdimm subsystem, so the scope
> of
> my review is more on the ocxl + misc issues side.
>
> A few minor checkpatch warnings that don't matter all that much:
>
> https://openpower.xyz/job/snowpatch/job/snowpatch-linux-checkpatch/11786//artifact/linux/checkpatch.log
>
> A few other comments below.
>
> > 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);
>
> Out of scope for this patch - given that we use memcpy_mcsafe in the
> config read, does it make sense to change memcpy_flushcache to be
> mcsafe
> as well?
>

Aneesh has confirmed that stores don't generate machine checks.

> > +
> > + 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];
>
> inb4 mpe tells you to Reverse Christmas Tree
>

-1, petty :P

> > +
> > + // 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)
>
> The lack of a kerneldoc comment here is inconsistent :)
>
> > +{
> > + 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;
> > + 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;
> > + }
> > + } 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;
> > + 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;
> > +
> > + pci_set_drvdata(pdev, ocxlpmem);
> > +
> > + ocxlpmem->ocxl_fn = ocxl_function_open(pdev);
> > + if (IS_ERR(ocxlpmem->ocxl_fn)) {
> > + kfree(ocxlpmem);
>
> You can't free this yet...

Whoops

>
> > + pci_set_drvdata(pdev, NULL);
> > + dev_err(&pdev->dev, "failed to open OCXL function\n");
> > + rc = PTR_ERR(ocxlpmem->ocxl_fn);
> > + 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");
> > + rc = -ENXIO;
> > + goto err;
>
> Meanwhile in this case, I think ocxlpmem and ocxlpmem->ocxl_fn get
> leaked (it's before ocxlpmem_register(), so the cleanup handler
> hasn't
> been registered).
>
> Add some new error labels for these two paths?
>

Ok

> > + }
> > +
> > + 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
> > + */
> > +
> > + 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,
> > +};
> > +
> > +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;
> > +};
>
> Hmm, given this struct serves no purpose other than associating an
> ocxl_fn with a pci_dev, and special handling for function 0 is
> probably
> going to be a common pattern in ocxl dependent drivers, perhaps we
> should export a function from ocxl that converts ocxl_fn -> pci_dev,
> and
> then you can just point the drvdata straight at the ocxl_fn?
>

Yup, the struct is vestigial, I'll remove it and deal directly with the
ocxl_fn instead.

>
> > +
> > +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

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