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Subject[PATCH v8 4/5] ndctl/papr_scm,uapi: Add support for PAPR nvdimm specific methods
Date
Introduce support for PAPR NVDIMM Specific Methods (PDSM) in papr_scm
module and add the command family to the white list of NVDIMM command
sets. Also advertise support for ND_CMD_CALL for the nvdimm
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: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
---
Changelog:

v7..v8:
* Removed the 'payload_offset' field from 'struct
nd_pdsm_cmd_pkg'. Instead command payload is always assumed to start
at 'nd_pdsm_cmd_pkg.payload'. [ Aneesh ]
* To enable introducing new fields to 'struct nd_pdsm_cmd_pkg',
'reserved' field of 10-bytes is introduced. [ Aneesh ]
* Fixed a typo in "Backward Compatibility" section of papr_scm_pdsm.h
[ Ira ]

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 | 136 ++++++++++++++++++
arch/powerpc/platforms/pseries/papr_scm.c | 101 ++++++++++++-
include/uapi/linux/ndctl.h | 1 +
3 files changed, 232 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..c4bae3208e73
--- /dev/null
+++ b/arch/powerpc/include/uapi/asm/papr_scm_pdsm.h
@@ -0,0 +1,136 @@
+/* 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
+ * envelope 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 accessible via 'nd_pdsm_cmd_pkg.payload' field.
+ * There is reserved field that can used to introduce new fields to the
+ * structure in future. It also tries to ensure that 'nd_pdsm_cmd_pkg.payload'
+ * lies at a 8-byte boundary.
+ *
+ * +-------------+---------------------+---------------------------+
+ * | 64-Bytes | 16-Bytes | Max 176-Bytes |
+ * +-------------+---------------------+---------------------------+
+ * | nd_pdsm_cmd_pkg | |
+ * |-------------+ | |
+ * | nd_cmd_pkg | | |
+ * +-------------+---------------------+---------------------------+
+ * | nd_family | | |
+ * | nd_size_out | cmd_status | |
+ * | nd_size_in | payload_version | payload |
+ * | nd_command | reserved | |
+ * | 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.
+ * 'reserved' : Not used and reserved for future.
+ *
+ * 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 176 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.
+ *
+ * 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 Y > X.
+ * 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 reserved[5]; /* Ignored and to be used in future */
+ __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 *)(pcmd->payload);
+}
+
+#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 010cd9aae488..fcb8afee97dc 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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