nfit, libnvdimm: limited/whitelisted dimm command marshaling mechanism

There are currently 4 known similar but incompatible definitions of the
command sets that can be sent to an NVDIMM through ACPI.  It is also
clear that future platform generations (ACPI or not) will continue to
revise and extend the DIMM command set as new devices and use cases
arrive.

It is obviously untenable to continue to proliferate divergence
of these command definitions, and to that end a standardization process
has begun to provide for a unified specification.  However, that leaves a
problem about what to do with this first generation where vendors are
already shipping divergence.

The Linux kernel can support these initial diverged platforms without
giving platform-firmware free reign to continue to diverge and compound
kernel maintenance overhead.  The kernel implementation can encourage
standardization in two ways:

1/ Require that any function code that userspace wants to send be
   explicitly white-listed in the implementation.  For ACPI this means
   function codes marked as supported by acpi_check_dsm() may
   only be invoked if they appear in the white-list.  A function must be
   publicly documented before it is added to the white-list.

2/ The above restrictions can be trivially bypassed by using the
   "vendor-specific" payload command.  However, since vendor-specific
   commands are by definition not publicly documented and have the
   potential to corrupt the kernel's view of the dimm state, we provide a
   toggle to disable vendor-specific operations.  Enabling undefined
   behavior is a policy decision that can be made by the platform owner
   and encourages firmware implementations to choose public over
   private command implementations.

Based on an initial patch from Jerry Hoemann
Cc: Jerry Hoemann <jerry.hoemann@hpe.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h
index 7cc28ab05b87..45daa0be5ff9 100644
--- a/include/uapi/linux/ndctl.h
+++ b/include/uapi/linux/ndctl.h
@@ -125,6 +125,7 @@ enum {
         ND_CMD_VENDOR_EFFECT_LOG_SIZE = 7,
         ND_CMD_VENDOR_EFFECT_LOG = 8,
         ND_CMD_VENDOR = 9,
+        ND_CMD_CALL = 10,
 };
 
 enum {
@@ -158,6 +159,7 @@ static inline const char *nvdimm_cmd_name(unsigned cmd)
                 [ND_CMD_VENDOR_EFFECT_LOG_SIZE] = "effect_size",
                 [ND_CMD_VENDOR_EFFECT_LOG] = "effect_log",
                 [ND_CMD_VENDOR] = "vendor",
+                [ND_CMD_CALL] = "cmd_call",
         };
 
         if (cmd < ARRAY_SIZE(names) && names[cmd])
@@ -224,4 +226,44 @@ enum ars_masks {
         ARS_STATUS_MASK = 0x0000FFFF,
         ARS_EXT_STATUS_SHIFT = 16,
 };
+
+/*
+ * struct nd_cmd_pkg
+ *
+ * is a wrapper to a quasi pass thru interface for invoking firmware
+ * associated with nvdimms.
+ *
+ * INPUT PARAMETERS
+ *
+ * nd_family corresponds to the firmware (e.g. DSM) interface.
+ *
+ * nd_command are the function index advertised by the firmware.
+ *
+ * nd_size_in is the size of the input parameters being passed to firmware
+ *
+ * OUTPUT PARAMETERS
+ *
+ * nd_fw_size is the size of the data firmware wants to return for
+ * the call.  If nd_fw_size is greater than size of nd_size_out, only
+ * the first nd_size_out bytes are returned.
+ */
+
+struct nd_cmd_pkg {
+        __u64   nd_family;              /* family of commands */
+        __u64   nd_command;
+        __u32   nd_size_in;             /* INPUT: size of input args */
+        __u32   nd_size_out;            /* INPUT: size of payload */
+        __u32   nd_reserved2[9];        /* reserved must be zero */
+        __u32   nd_fw_size;             /* OUTPUT: size fw wants to return */
+        unsigned char nd_payload[];     /* Contents of call      */
+};
+
+/* These NVDIMM families represent pre-standardization command sets */
+#define NVDIMM_FAMILY_INTEL 0
+#define NVDIMM_FAMILY_HPE1 1
+#define NVDIMM_FAMILY_HPE2 2
+
+#define ND_IOCTL_CALL                   _IOWR(ND_IOCTL, ND_CMD_CALL,\
+                                        struct nd_cmd_pkg)
+
 #endif /* __NDCTL_H__ */