Re: [RESEND PATCH v9 4/5] ndctl/papr_scm,uapi: Add support for PAPR nvdimm specific methods

On Thu, Jun 04, 2020 at 01:58:00AM +0530, Vaibhav Jain wrote: Yea I see that now... Coming from a networking background I find that odd... :-/ Usually 'size' in a header includes all data after that header. Because header A knows nothing of the rest of the 'payload'... FWIW you could define nd_size_in anyway you want because you are not really sending any payload back from firmware directly. But I suppose I can live with it. Ira > > > 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 <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 */ > >> > @@ -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(a)lists.01.org > >> To unsubscribe send an email to linux-nvdimm-leave(a)lists.01.org > > -- > Cheers > ~ Vaibhav