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V" , Michael Ellerman , Steven Rostedt Subject: Re: [RESEND PATCH v9 4/5] ndctl/papr_scm,uapi: Add support for PAPR nvdimm specific methods Message-ID: <20200602210553.GG1505637@iweiny-DESK2.sc.intel.com> References: <20200602101438.73929-1-vaibhav@linux.ibm.com> <20200602101438.73929-5-vaibhav@linux.ibm.com> <20200602205148.GF1505637@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200602205148.GF1505637@iweiny-DESK2.sc.intel.com> User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 02, 2020 at 01:51:49PM -0700, 'Ira Weiny' wrote: > On Tue, Jun 02, 2020 at 03:44:37PM +0530, Vaibhav Jain wrote: ... > > + > > +/* > > + * 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 | | | > > + * +-------------+---------------------+---------------------------+ One more comment WRT nd_size_[in|out]. I know that it is defined as the size of the FW payload but normally when you nest headers 'size' in Header A represents everything after Header A, including Header B. In this case that would be including nd_pdsm_cmd_pkg... It looks like that is not what you have done? Or perhaps I missed it? Ira > > + * > > + * 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 > ^^^^^ > ... the ... > > > + * 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. > > Please see this thread for an example why versions are a bad idea in UAPIs: > > https://lkml.org/lkml/2020/3/26/213 > > While the use of version is different in that thread the fundamental issues are > the same. You end up with some weird matrix of supported features and > structure definitions. For example, you are opening up the possibility of > changing structures with a different version for no good reason. > > Also having the user query with version Z and get back version X (older) is > odd. Generally if the kernel does not know about a feature (ie version Z of > the structure) it should return -EINVAL and let the user figure out what to do. > The user may just give up or they could try a different query. > > > + */ > > + > > +/* 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[5]; /* Ignored and to be used in future */ > > How do you know when reserved is used for something else in the future? Is > reserved guaranteed (and checked by the code) to be 0? > > > + __u16 payload_version; /* In/Out: version of the payload */ > > Why is payload_version after reserved? > > > + __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, > > +}; > > + > > +/* 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_PDSM_H_ */ > > diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c > > index 149431594839..5e2237e7ec08 100644 > > --- a/arch/powerpc/platforms/pseries/papr_scm.c > > +++ b/arch/powerpc/platforms/pseries/papr_scm.c > > @@ -15,13 +15,15 @@ > > #include > > > > #include > > +#include > > > > #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 */ > > s/date/data > > > + 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) { > > + 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 */ > > I assume the first command to be implemented also checks the { nd_command, > payload_version, payload length } for correctness? > > > + 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_PDSM_MIN || > > + call_pkg->hdr.nd_command >= PAPR_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; > > Why is this needed? AFAICT The caller of papr_scm_ndctl does not specify null > and you did not change it. > > > + > > + *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; > > Is this change related? If there is a bug where there is a caller of > papr_scm_ndctl() with cmd_rc == NULL this should be a separate patch to fix > that issue. > > Ira > > > } > > > > 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..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 > > > _______________________________________________ > Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org > To unsubscribe send an email to linux-nvdimm-leave@lists.01.org