Message-ID: <CAPcyv4ia7MQ0LjmNrt82WPGhBPrJG4Y1gb5zmVkaUMNVo-EnCw@mail.gmail.com>
Date:   Wed, 1 Apr 2020 12:35:24 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Alastair D'Silva" <alastair@...ilva.org>
Cc:     "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        "Oliver O'Halloran" <oohall@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        Anton Blanchard <anton@...abs.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Cédric Le Goater <clg@...d.org>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kurz <groug@...d.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH v4 10/25] nvdimm: Add driver for OpenCAPI Persistent Memory

On Wed, Apr 1, 2020 at 1:49 AM Dan Williams <dan.j.williams@...el.com> wrote:
>
> On Sun, Mar 29, 2020 at 10:23 PM Alastair D'Silva <alastair@...ilva.org> wrote:
> >
> > 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. ndctl_config_read/write/size() provide
> > callbacks to libnvdimm to access the metadata.
> >
> > Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
> > ---
> >  drivers/nvdimm/Kconfig         |   2 +
> >  drivers/nvdimm/Makefile        |   1 +
> >  drivers/nvdimm/ocxl/Kconfig    |  15 ++
> >  drivers/nvdimm/ocxl/Makefile   |   7 +
> >  drivers/nvdimm/ocxl/main.c     | 476 +++++++++++++++++++++++++++++++++
> >  drivers/nvdimm/ocxl/ocxlpmem.h |  23 ++
> >  6 files changed, 524 insertions(+)
> >  create mode 100644 drivers/nvdimm/ocxl/Kconfig
> >  create mode 100644 drivers/nvdimm/ocxl/Makefile
> >  create mode 100644 drivers/nvdimm/ocxl/main.c
> >  create mode 100644 drivers/nvdimm/ocxl/ocxlpmem.h
> >
> > diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
> > index b7d1eb38b27d..368328637182 100644
> > --- a/drivers/nvdimm/Kconfig
> > +++ b/drivers/nvdimm/Kconfig
> > @@ -131,4 +131,6 @@ config NVDIMM_TEST_BUILD
> >           core devm_memremap_pages() implementation and other
> >           infrastructure.
> >
> > +source "drivers/nvdimm/ocxl/Kconfig"
> > +
> >  endif
> > diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
> > index 29203f3d3069..bc02be11c794 100644
> > --- a/drivers/nvdimm/Makefile
> > +++ b/drivers/nvdimm/Makefile
> > @@ -33,3 +33,4 @@ libnvdimm-$(CONFIG_NVDIMM_KEYS) += security.o
> >  TOOLS := ../../tools
> >  TEST_SRC := $(TOOLS)/testing/nvdimm/test
> >  obj-$(CONFIG_NVDIMM_TEST_BUILD) += $(TEST_SRC)/iomap.o
> > +obj-$(CONFIG_LIBNVDIMM) += ocxl/
> > diff --git a/drivers/nvdimm/ocxl/Kconfig b/drivers/nvdimm/ocxl/Kconfig
> > new file mode 100644
> > index 000000000000..c5d927520920
> > --- /dev/null
> > +++ b/drivers/nvdimm/ocxl/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
>
> Does OXCL_PMEM itself have any CONFIG_ZONE_DEVICE dependencies? That's
> more a function of CONFIG_DEV_DAX and CONFIG_FS_DAX. Doesn't OCXL
> already depend on CONFIG_PCI?
>
>
> > +       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/drivers/nvdimm/ocxl/Makefile b/drivers/nvdimm/ocxl/Makefile
> > new file mode 100644
> > index 000000000000..e0e8ade1987a
> > --- /dev/null
> > +++ b/drivers/nvdimm/ocxl/Makefile
> > @@ -0,0 +1,7 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +ccflags-$(CONFIG_PPC_WERROR)   += -Werror
> > +
> > +obj-$(CONFIG_OCXL_PMEM) += ocxlpmem.o
> > +
> > +ocxlpmem-y := main.o
> > \ No newline at end of file
> > diff --git a/drivers/nvdimm/ocxl/main.c b/drivers/nvdimm/ocxl/main.c
> > new file mode 100644
> > index 000000000000..c0066fedf9cc
> > --- /dev/null
> > +++ b/drivers/nvdimm/ocxl/main.c
> > @@ -0,0 +1,476 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +// Copyright 2020 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 "ocxlpmem.h"
> > +
> > +static const struct pci_device_id pci_tbl[] = {
> > +       { PCI_DEVICE(PCI_VENDOR_ID_IBM, 0x0625), },
> > +       { }
> > +};
> > +
> > +MODULE_DEVICE_TABLE(pci, 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 || !lpc_mem->start)
> > +               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 = "ocxlpmem";
> > +       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;
> > +       ocxlpmem->nd_set.cookie2 = fn_config->serial;
> > +
> > +       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;
> > +
> > +       free_minor(ocxlpmem);
> > +
> > +       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);
> > +
> > +       pci_dev_put(ocxlpmem->pdev);
> > +
> > +       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);
>
> You lost me, why does this need it's own ioctl path and device node?
> I'd expect you you'd tunnel the commands you need through the existing
> infrastructure ideally with an eye for cross-arch compatibility. This
> is a fundamental concern that probably has significant implications
> for what follows.

At a minimum this device registration should move to the end of the
patchset once all the libnvdimm generic enabling is done. Even then I
think the libnvdimm core has all the hooks you need to provide device
specific enabling *through* the existing interfaces. Have a look at
the how the ACPI NFIT bus driver provides "nfit/" scoped sysfs
attributes and tunnels "struct nd_cmd_pkg" ioctl invocations to either
the bus or "dimm" level device objects. The dimm security model is an
example of an implementation that wraps a libnvdimm-generic sysfs
front-end to an intel-specific-device backend. It would be unfortunate
to need to invent another ABI.

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