Subject: Re: [PATCH v11 5/6] ndctl/papr_scm, uapi: Add support for PAPR nvdimm specific methods

From: Vaibhav Jain <[email-masked]>
Date: Mon, 08 Jun 2020 23:40:09 +0530

Ira Weiny <[email-masked]> writes:

> On Sun, Jun 07, 2020 at 06:43:38PM +0530, Vaibhav Jain wrote:
>> Introduce support for PAPR NVDIMM Specific Methods (PDSM) in papr_scm
>> module and add the command family NVDIMM_FAMILY_PAPR 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_pdsm.h' which
>> defines a new 'struct nd_pdsm_cmd_pkg' header. This header is used
>> to communicate the PDSM request via member
>> 'nd_cmd_pkg.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" <[email-masked]>
>> Cc: Dan Williams <[email-masked]>
>> Cc: Michael Ellerman <[email-masked]>
>> Cc: Ira Weiny <[email-masked]>
>> Signed-off-by: Vaibhav Jain <[email-masked]>
>> ---
>> Changelog:
>> 
>> v10..v11:
>> * Moved in-lines 'nd_pdsm_cmd_pkg()' and 'pdsm_cmd_to_payload()' from
>>   'papr_pdsm.h' header to 'papr_scm.c'. The avoids a potential license
>>   incompatibility issue with non-GPL-2.0 user-space code trying to
>>   include the header in its code. [ Ira ]
>> * Verified papr_pdsm.h with UAPI_HEADER_TEST config.
>> * Moved the is_cmd_valid() check in papr_scm_ndctl() before check for
>>   cmd_rc == NULL. This prevents cmd_rc to be updated in case the
>>   nd-cmd is invalid or unknown.
>> 
>> v9..v10:
>> * Simplified 'struct nd_pdsm_cmd_pkg' by removing the
>>   'payload_version' field.
>> * Removed the corrosponding documentation on versioning and backward
>>   compatibility from 'papr_pdsm.h'
>> * Reduced the size of reserved fields to 4-bytes making 'struct
>>   nd_pdsm_cmd_pkg' 64 + 8 bytes long.
>> * Updated is_cmd_valid() to enforce validation checks on pdsm
>>   commands. [ Dan Williams ]
>> * Added check for reserved fields being set to '0' in is_cmd_valid()
>>   [ Ira ]
>> * Moved changes for checking cmd_rc == NULL and logging improvements
>>   to a separate prelim patch [ Ira ].
>> * Moved  pdsm package validation checks from papr_scm_service_pdsm()
>>   to is_cmd_valid().
>> * Marked papr_scm_service_pdsm() return type as 'void' since errors
>>   are reported in nd_pdsm_cmd_pkg.cmd_status field.
>> 
>> Resend:
>> * Added ack from Aneesh.
>> 
>> v8..v9:
>> * Reduced the usage of term SCM replacing it with appropriate
>>   replacement [ Dan Williams, Aneesh ]
>> * Renamed 'papr_scm_pdsm.h' to 'papr_pdsm.h'
>> * s/PAPR_SCM_PDSM_*/PAPR_PDSM_*/g
>> * s/NVDIMM_FAMILY_PAPR_SCM/NVDIMM_FAMILY_PAPR/g
>> * Minor updates to 'papr_psdm.h' to replace usage of term 'SCM'.
>> * Minor update to patch description.
>> 
>> 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_pdsm.h |  84 +++++++++++++++
>>  arch/powerpc/platforms/pseries/papr_scm.c | 126 +++++++++++++++++++++-
>>  include/uapi/linux/ndctl.h                |   1 +
>>  3 files changed, 207 insertions(+), 4 deletions(-)
>>  create mode 100644 arch/powerpc/include/uapi/asm/papr_pdsm.h
>> 
>> diff --git a/arch/powerpc/include/uapi/asm/papr_pdsm.h b/arch/powerpc/include/uapi/asm/papr_pdsm.h
>> new file mode 100644
>> index 000000000000..df2447455cfe
>> --- /dev/null
>> +++ b/arch/powerpc/include/uapi/asm/papr_pdsm.h
>> @@ -0,0 +1,84 @@
>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
>> +/*
>> + * PAPR nvDimm Specific Methods (PDSM) and structs for libndctl
>> + *
>> + * (C) Copyright IBM 2020
>> + *
>> + * Author: Vaibhav Jain <vaibhav at linux.ibm.com>
>> + */
>> +
>> +#ifndef _UAPI_ASM_POWERPC_PAPR_PDSM_H_
>> +#define _UAPI_ASM_POWERPC_PAPR_PDSM_H_
>> +
>> +#include <linux/types.h>
>> +#include <linux/ndctl.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  |       8-Bytes       |       Max 184-Bytes       |
>> + *  +-------------+---------------------+---------------------------+
>> + *  |               nd_pdsm_cmd_pkg     |                           |
>> + *  |-------------+                     |                           |
>> + *  |  nd_cmd_pkg |                     |                           |
>> + *  +-------------+---------------------+---------------------------+
>> + *  | nd_family   |                     |                           |
>> + *  | nd_size_out | cmd_status          |                           |
>> + *  | nd_size_in  | reserved            |     payload               |
>> + *  | nd_command  |                     |                           |
>> + *  | 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.
>> + * 'reserved'		: Not used, reserved for future and should be set to 0.
>> + *
>> + * 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
>
> 'around'?
>
>> (ignoring any padding that
>> + * the compiler may silently introduce).
>
> When building user interfaces like this you have to be more exact.  I think the
> code is fine but you can't have the compiler silently moving things around or
> have different compilers move things differently between the user app and the
> kernel.  So these statements are not correct.
>
Sure, will update these comment block to better express the '__packed' gcc
attribute semantics for struct nd_pdsm_cmd_pkg.

~ Vaibhav

> Ira
>
>> + *
>> + */
>> +
>> +/* PDSM-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[2];	/* Ignored and to be used in future */
>> +	__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_pdsm {
>> +	PAPR_PDSM_MIN = 0x0,
>> +	PAPR_PDSM_MAX,
>> +};
>> +
>> +#endif /* _UAPI_ASM_POWERPC_PAPR_PDSM_H_ */
>> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
>> index 692ad3d79826..167fcf0e249d 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_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 */
>> @@ -89,6 +91,21 @@ struct papr_scm_priv {
>>  	u64 health_bitmap;
>>  };
>>  
>> +/* 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);
>> +}
>> +
>>  static int drc_pmem_bind(struct papr_scm_priv *p)
>>  {
>>  	unsigned long ret[PLPAR_HCALL_BUFSIZE];
>> @@ -349,17 +366,113 @@ static int papr_scm_meta_set(struct papr_scm_priv *p,
>>  	return 0;
>>  }
>>  
>> +/*
>> + * Do a sanity checks on the inputs args to dimm-control function and return
>> + * '0' if valid. This also does validation on 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;
>> +	struct nd_cmd_pkg *nd_cmd;
>> +	struct papr_scm_priv *p;
>> +	enum papr_pdsm pdsm;
>> +
>> +	/* Only dimm-specific calls are supported atm */
>> +	if (!nvdimm)
>> +		return -EINVAL;
>> +
>> +	/* get the provider data 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;
>> +	}
>> +
>> +	/* For CMD_CALL verify pdsm request */
>> +	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 nd_cmd_pkg.nd_family is correct */
>> +		nd_cmd = (struct nd_cmd_pkg *)buf;
>> +		if (nd_cmd->nd_family != NVDIMM_FAMILY_PAPR) {
>> +			dev_dbg(&p->pdev->dev, "Invalid pkg family=0x%llx\n",
>> +				nd_cmd->nd_family);
>> +			return -EINVAL;
>> +		}
>> +
>> +		/* Get the pdsm request package and the command */
>> +		pkg = nd_to_pdsm_cmd_pkg(nd_cmd);
>> +		pdsm = pkg->hdr.nd_command;
>> +
>> +		/* Verify if the psdm command is valid */
>> +		if (pdsm <= PAPR_PDSM_MIN || pdsm >= PAPR_PDSM_MAX) {
>> +			dev_dbg(&p->pdev->dev, "PDSM[0x%x]: Invalid PDSM\n", pdsm);
>> +			return -EINVAL;
>> +		}
>> +
>> +		/* We except a payload with all PDSM commands */
>> +		if (!pdsm_cmd_to_payload(pkg)) {
>> +			dev_dbg(&p->pdev->dev, "PDSM[0x%x]: Empty payload\n", pdsm);
>> +			return -EINVAL;
>> +		}
>> +
>> +		/* Ensure reserved fields of the pdsm header are set to 0 */
>> +		if (pkg->reserved[0] || pkg->reserved[1]) {
>> +			dev_dbg(&p->pdev->dev,
>> +				"PDSM[0x%x]: Invalid reserved field usage\n", pdsm);
>> +			return -EINVAL;
>> +		}
>> +	}
>> +
>> +	/* Let the command be further processed */
>> +	return 0;
>> +}
>> +
>> +/*
>> + * For a given pdsm request call an appropriate service function.
>> + * Returns errors if any while handling the pdsm command package.
>> + */
>> +static int papr_scm_service_pdsm(struct papr_scm_priv *p,
>> +				 struct nd_pdsm_cmd_pkg *pkg)
>> +{
>> +	const enum papr_pdsm pdsm = pkg->hdr.nd_command;
>> +
>> +	dev_dbg(&p->pdev->dev, "PDSM[0x%x]: Servicing..\n", pdsm);
>> +
>> +	/* Call pdsm service function */
>> +	switch (pdsm) {
>> +	default:
>> +		dev_dbg(&p->pdev->dev, "PDSM[0x%x]: Unsupported PDSM request\n",
>> +			pdsm);
>> +		pkg->cmd_status = -ENOENT;
>> +		break;
>> +	}
>> +
>> +	return pkg->cmd_status;
>> +}
>> +
>>  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 nd_pdsm_cmd_pkg *call_pkg = NULL;
>>  	struct papr_scm_priv *p;
>>  	int rc;
>>  
>> -	/* Only dimm-specific calls are supported atm */
>> -	if (!nvdimm)
>> -		return -EINVAL;
>> +	rc = is_cmd_valid(nvdimm, cmd, buf, buf_len);
>> +	if (rc) {
>> +		pr_debug("Invalid cmd=0x%x. Err=%d\n", cmd, rc);
>> +		return rc;
>> +	}
>>  
>>  	/* Use a local variable in case cmd_rc pointer is NULL */
>>  	if (!cmd_rc)
>> @@ -385,6 +498,11 @@ 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:
>>  		dev_dbg(&p->pdev->dev, "Unknown command = %d\n", cmd);
>>  		return -EINVAL;
>> diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h
>> index de5d90212409..0e09dc5cec19 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 5
>>  
>>  #define ND_IOCTL_CALL			_IOWR(ND_IOCTL, ND_CMD_CALL,\
>>  					struct nd_cmd_pkg)
>> -- 
>> 2.26.2
>> 

-- 
Cheers
~ Vaibhav