Re: [RESEND PATCH v7 4/5] ndctl/papr_scm,uapi: Add support for PAPR nvdimm specific methods

Ira Weiny
2020-05-20T15:32:14Z

On Wed, May 20, 2020 at 12:30:57AM +0530, Vaibhav Jain wrote:
> Introduce support for Papr nvDimm Specific Methods (PDSM) in papr_scm
> modules and add the command family to the white list of NVDIMM command
> sets. Also advertise support for ND_CMD_CALL for the dimm
> command mask and implement necessary scaffolding in the module to
> handle ND_CMD_CALL ioctl and PDSM requests that we receive.
>
> The layout of the PDSM request as we expect from libnvdimm/libndctl is
> described in newly introduced uapi header 'papr_scm_pdsm.h' which
> defines a new 'struct nd_pdsm_cmd_pkg' header. This header is used
> to communicate the PDSM request via member
> 'nd_pkg_papr_scm->nd_command' and size of payload that need to be
> sent/received for servicing the PDSM.
>
> A new function is_cmd_valid() is implemented that reads the args to
> papr_scm_ndctl() and performs sanity tests on them. A new function
> papr_scm_service_pdsm() is introduced and is called from
> papr_scm_ndctl() in case of a PDSM request is received via ND_CMD_CALL
> command from libnvdimm.
>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> ---
> Changelog:
>
> Resend:
> * None
>
> v6..v7 :
> * Removed the re-definitions of __packed macro from papr_scm_pdsm.h
> [Mpe].
> * Removed the usage of __KERNEL__ macros in papr_scm_pdsm.h [Mpe].
> * Removed macros that were unused in papr_scm.c from papr_scm_pdsm.h
> [Mpe].
> * Made functions defined in papr_scm_pdsm.h as static inline. [Mpe]
>
> v5..v6 :
> * Changed the usage of the term DSM to PDSM to distinguish it from the
> ACPI term [ Dan Williams ]
> * Renamed papr_scm_dsm.h to papr_scm_pdsm.h and updated various struct
> to reflect the new terminology.
> * Updated the patch description and title to reflect the new terminology.
> * Squashed patch to introduce new command family in 'ndctl.h' with
> this patch [ Dan Williams ]
> * Updated the papr_scm_pdsm method starting index from 0x10000 to 0x0
> [ Dan Williams ]
> * Removed redundant license text from the papr_scm_psdm.h file.
> [ Dan Williams ]
> * s/envelop/envelope/ at various places [ Dan Williams ]
> * Added '__packed' attribute to command package header to gaurd
> against different compiler adding paddings between the fields.
> [ Dan Williams]
> * Converted various pr_debug to dev_debug [ Dan Williams ]
>
> v4..v5 :
> * None
>
> v3..v4 :
> * None
>
> v2..v3 :
> * Updated the patch prefix to 'ndctl/uapi' [Aneesh]
>
> v1..v2 :
> * None
> ---
> arch/powerpc/include/uapi/asm/papr_scm_pdsm.h | 134 ++++++++++++++++++
> arch/powerpc/platforms/pseries/papr_scm.c | 101 ++++++++++++-
> include/uapi/linux/ndctl.h | 1 +
> 3 files changed, 230 insertions(+), 6 deletions(-)
> create mode 100644 arch/powerpc/include/uapi/asm/papr_scm_pdsm.h
>
> diff --git a/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h b/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h
> new file mode 100644
> index 000000000000..671693439c1c
> --- /dev/null
> +++ b/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h
> @@ -0,0 +1,134 @@
> +/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
> +/*
> + * PAPR-SCM Dimm specific methods (PDSM) and structs for libndctl
> + *
> + * (C) Copyright IBM 2020
> + *
> + * Author: Vaibhav Jain <vaibhav at linux.ibm.com>
> + */
> +
> +#ifndef _UAPI_ASM_POWERPC_PAPR_SCM_PDSM_H_
> +#define _UAPI_ASM_POWERPC_PAPR_SCM_PDSM_H_
> +
> +#include <linux/types.h>
> +
> +/*
> + * PDSM Envelope:
> + *
> + * The ioctl ND_CMD_CALL transfers data between user-space and kernel via
> + * 'envelopes' which consists of a header and user-defined payload sections.
> + * The header is described by 'struct nd_pdsm_cmd_pkg' which expects a
> + * payload following it and offset of which relative to the struct is provided
> + * by 'nd_pdsm_cmd_pkg.payload_offset'. *
> + *
> + * +-------------+---------------------+---------------------------+
> + * | 64-Bytes | 8-Bytes | Max 184-Bytes |
> + * +-------------+---------------------+---------------------------+
> + * | nd_pdsm_cmd_pkg | |
> + * |-------------+ | |
> + * | nd_cmd_pkg | | |
> + * +-------------+---------------------+---------------------------+
> + * | nd_family | | |
> + * | nd_size_out | cmd_status | |
> + * | nd_size_in | payload_version | PAYLOAD |
> + * | nd_command | payload_offset -----> |
> + * | nd_fw_size | | |
> + * +-------------+---------------------+---------------------------+
> + *
> + * PDSM Header:
> + *
> + * The header is defined as 'struct nd_pdsm_cmd_pkg' which embeds a
> + * 'struct nd_cmd_pkg' instance. The PDSM command is assigned to member
> + * 'nd_cmd_pkg.nd_command'. Apart from size information of the envelope which is
> + * contained in 'struct nd_cmd_pkg', the header also has members following
> + * members:
> + *
> + * 'cmd_status' : (Out) Errors if any encountered while servicing PDSM.
> + * 'payload_version' : (In/Out) Version number associated with the payload.
> + * 'payload_offset' : (In)Relative offset of payload from start of envelope.
> + *
> + * PDSM Payload:
> + *
> + * The layout of the PDSM Payload is defined by various structs shared between
> + * papr_scm and libndctl so that contents of payload can be interpreted. During
> + * servicing of a PDSM the papr_scm module will read input args from the payload
> + * field by casting its contents to an appropriate struct pointer based on the
> + * PDSM command. Similarly the output of servicing the PDSM command will be
> + * copied to the payload field using the same struct.
> + *
> + * 'libnvdimm' enforces a hard limit of 256 bytes on the envelope size, which
> + * leaves around 184 bytes for the envelope payload (ignoring any padding that
> + * the compiler may silently introduce).
> + *
> + * Payload Version:
> + *
> + * A 'payload_version' field is present in PDSM header that indicates a specific
> + * version of the structure present in PDSM Payload for a given PDSM command.
> + * This provides backward compatibility in case the PDSM Payload structure
> + * evolves and different structures are supported by 'papr_scm' and 'libndctl'.
> + *
> + * When sending a PDSM Payload to 'papr_scm', 'libndctl' should send the version
> + * of the payload struct it supports via 'payload_version' field. The 'papr_scm'
> + * module when servicing the PDSM envelope checks the 'payload_version' and then
> + * uses 'payload struct version' == MIN('payload_version field',
> + * 'max payload-struct-version supported by papr_scm') to service the PDSM.
> + * After servicing the PDSM, 'papr_scm' put the negotiated version of payload
> + * struct in returned 'payload_version' field.

FWIW many people believe using a size rather than version is more sustainable.
It is expected that new payload structures are larger (more features) than the
previous payload structure.

I can't find references at the moment through.

What does payload_version provide us that the command size in/out does not?

> + *
> + * Libndctl on receiving the envelope back from papr_scm again checks the
> + * 'payload_version' field and based on it use the appropriate version dsm
> + * struct to parse the results.
> + *
> + * Backward Compatibility:
> + *
> + * Above scheme of exchanging different versioned PDSM struct between libndctl
> + * and papr_scm should provide backward compatibility until following two
> + * assumptions/conditions when defining new PDSM structs hold:
> + *
> + * Let T(X) = { set of attributes in PDSM struct 'T' versioned X }
> + *
> + * 1. T(X) is a proper subset of T(Y) if X > Y.

Proper superset? Or Y > X?

Ira

> + * i.e Each new version of PDSM struct should retain existing struct
> + * attributes from previous version
> + *
> + * 2. If an entity (libndctl or papr_scm) supports a PDSM struct T(X) then
> + * it should also support T(1), T(2)...T(X - 1).
> + * i.e When adding support for new version of a PDSM struct, libndctl
> + * and papr_scm should retain support of the existing PDSM struct
> + * version they support.
> + */
> +
> +/* Papr-scm-header + payload expected with ND_CMD_CALL ioctl from libnvdimm */
> +struct nd_pdsm_cmd_pkg {
> + struct nd_cmd_pkg hdr; /* Package header containing sub-cmd */
> + __s32 cmd_status; /* Out: Sub-cmd status returned back */
> + __u16 payload_offset; /* In: offset from start of struct */
> + __u16 payload_version; /* In/Out: version of the payload */
> + __u8 payload[]; /* In/Out: Sub-cmd data buffer */
> +} __packed;
> +
> +/*
> + * Methods to be embedded in ND_CMD_CALL request. These are sent to the kernel
> + * via 'nd_pdsm_cmd_pkg.hdr.nd_command' member of the ioctl struct
> + */
> +enum papr_scm_pdsm {
> + PAPR_SCM_PDSM_MIN = 0x0,
> + PAPR_SCM_PDSM_MAX,
> +};
> +
> +/* Convert a libnvdimm nd_cmd_pkg to pdsm specific pkg */
> +static inline struct nd_pdsm_cmd_pkg *nd_to_pdsm_cmd_pkg(struct nd_cmd_pkg *cmd)
> +{
> + return (struct nd_pdsm_cmd_pkg *) cmd;
> +}
> +
> +/* Return the payload pointer for a given pcmd */
> +static inline void *pdsm_cmd_to_payload(struct nd_pdsm_cmd_pkg *pcmd)
> +{
> + if (pcmd->hdr.nd_size_in == 0 && pcmd->hdr.nd_size_out == 0)
> + return NULL;
> + else
> + return (void *)((__u8 *) pcmd + pcmd->payload_offset);
> +}
> +
> +#endif /* _UAPI_ASM_POWERPC_PAPR_SCM_PDSM_H_ */
> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
> index 142636e1a59f..ed4b49a6f1e1 100644
> --- a/arch/powerpc/platforms/pseries/papr_scm.c
> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
> @@ -15,13 +15,15 @@
> #include <linux/seq_buf.h>
>
> #include <asm/plpar_wrappers.h>
> +#include <asm/papr_scm_pdsm.h>
>
> #define BIND_ANY_ADDR (~0ul)
>
> #define PAPR_SCM_DIMM_CMD_MASK \
> ((1ul << ND_CMD_GET_CONFIG_SIZE) | \
> (1ul << ND_CMD_GET_CONFIG_DATA) | \
> - (1ul << ND_CMD_SET_CONFIG_DATA))
> + (1ul << ND_CMD_SET_CONFIG_DATA) | \
> + (1ul << ND_CMD_CALL))
>
> /* DIMM health bitmap bitmap indicators */
> /* SCM device is unable to persist memory contents */
> @@ -350,16 +352,97 @@ static int papr_scm_meta_set(struct papr_scm_priv *p,
> return 0;
> }
>
> +/*
> + * Validate the inputs args to dimm-control function and return '0' if valid.
> + * This also does initial sanity validation to ND_CMD_CALL sub-command packages.
> + */
> +static int is_cmd_valid(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
> + unsigned int buf_len)
> +{
> + unsigned long cmd_mask = PAPR_SCM_DIMM_CMD_MASK;
> + struct nd_pdsm_cmd_pkg *pkg = nd_to_pdsm_cmd_pkg(buf);
> + struct papr_scm_priv *p;
> +
> + /* Only dimm-specific calls are supported atm */
> + if (!nvdimm)
> + return -EINVAL;
> +
> + /* get the provider date from struct nvdimm */
> + p = nvdimm_provider_data(nvdimm);
> +
> + if (!test_bit(cmd, &cmd_mask)) {
> + dev_dbg(&p->pdev->dev, "Unsupported cmd=%u\n", cmd);
> + return -EINVAL;
> + } else if (cmd == ND_CMD_CALL) {
> +
> + /* Verify the envelope package */
> + if (!buf || buf_len < sizeof(struct nd_pdsm_cmd_pkg)) {
> + dev_dbg(&p->pdev->dev, "Invalid pkg size=%u\n",
> + buf_len);
> + return -EINVAL;
> + }
> +
> + /* Verify that the PDSM family is valid */
> + if (pkg->hdr.nd_family != NVDIMM_FAMILY_PAPR_SCM) {
> + dev_dbg(&p->pdev->dev, "Invalid pkg family=0x%llx\n",
> + pkg->hdr.nd_family);
> + return -EINVAL;
> +
> + }
> +
> + /* We except a payload with all PDSM commands */
> + if (pdsm_cmd_to_payload(pkg) == NULL) {
> + dev_dbg(&p->pdev->dev,
> + "Empty payload for sub-command=0x%llx\n",
> + pkg->hdr.nd_command);
> + return -EINVAL;
> + }
> + }
> +
> + /* Command looks valid */
> + return 0;
> +}
> +
> +static int papr_scm_service_pdsm(struct papr_scm_priv *p,
> + struct nd_pdsm_cmd_pkg *call_pkg)
> +{
> + /* unknown subcommands return error in packages */
> + if (call_pkg->hdr.nd_command <= PAPR_SCM_PDSM_MIN ||
> + call_pkg->hdr.nd_command >= PAPR_SCM_PDSM_MAX) {
> + dev_dbg(&p->pdev->dev, "Invalid PDSM request 0x%llx\n",
> + call_pkg->hdr.nd_command);
> + call_pkg->cmd_status = -EINVAL;
> + return 0;
> + }
> +
> + /* Depending on the DSM command call appropriate service routine */
> + switch (call_pkg->hdr.nd_command) {
> + default:
> + dev_dbg(&p->pdev->dev, "Unsupported PDSM request 0x%llx\n",
> + call_pkg->hdr.nd_command);
> + call_pkg->cmd_status = -ENOENT;
> + return 0;
> + }
> +}
> +
> static int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc,
> struct nvdimm *nvdimm, unsigned int cmd, void *buf,
> unsigned int buf_len, int *cmd_rc)
> {
> struct nd_cmd_get_config_size *get_size_hdr;
> struct papr_scm_priv *p;
> + struct nd_pdsm_cmd_pkg *call_pkg = NULL;
> + int rc;
>
> - /* Only dimm-specific calls are supported atm */
> - if (!nvdimm)
> - return -EINVAL;
> + /* Use a local variable in case cmd_rc pointer is NULL */
> + if (cmd_rc == NULL)
> + cmd_rc = &rc;
> +
> + *cmd_rc = is_cmd_valid(nvdimm, cmd, buf, buf_len);
> + if (*cmd_rc) {
> + pr_debug("Invalid cmd=0x%x. Err=%d\n", cmd, *cmd_rc);
> + return *cmd_rc;
> + }
>
> p = nvdimm_provider_data(nvdimm);
>
> @@ -381,13 +464,19 @@ static int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc,
> *cmd_rc = papr_scm_meta_set(p, buf);
> break;
>
> + case ND_CMD_CALL:
> + call_pkg = nd_to_pdsm_cmd_pkg(buf);
> + *cmd_rc = papr_scm_service_pdsm(p, call_pkg);
> + break;
> +
> default:
> - return -EINVAL;
> + dev_dbg(&p->pdev->dev, "Unknown command = %d\n", cmd);
> + *cmd_rc = -EINVAL;
> }
>
> dev_dbg(&p->pdev->dev, "returned with cmd_rc = %d\n", *cmd_rc);
>
> - return 0;
> + return *cmd_rc;
> }
>
> static ssize_t flags_show(struct device *dev,
> diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h
> index de5d90212409..99fb60600ef8 100644
> --- a/include/uapi/linux/ndctl.h
> +++ b/include/uapi/linux/ndctl.h
> @@ -244,6 +244,7 @@ struct nd_cmd_pkg {
> #define NVDIMM_FAMILY_HPE2 2
> #define NVDIMM_FAMILY_MSFT 3
> #define NVDIMM_FAMILY_HYPERV 4
> +#define NVDIMM_FAMILY_PAPR_SCM 5
>
> #define ND_IOCTL_CALL _IOWR(ND_IOCTL, ND_CMD_CALL,\
> struct nd_cmd_pkg)
> --
> 2.26.2
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