Re: [PATCH 2/2] powerpc/pseries: Add driver for PAPR SCM regions

On Tue, Oct 9, 2018 at 11:21 PM Oliver O'Halloran [off-list ref] wrote:

Does plpar_hcall sleep? Should there be a cond_resched() here if not?

+       } while (rc == H_BUSY);
+
+       if (rc) {
+               dev_err(&p->pdev->dev, "bind err: %lld\n", rc);
+               return -ENXIO;
+       }
+
+       p->bound_addr = be64_to_cpu(ret[1]);
+
+       dev_dbg(&p->pdev->dev, "bound drc %x to %pR\n", p->drc_index, &p->res);
+
+       return 0;
+}
+
+static int drc_pmem_unbind(struct papr_scm_priv *p)
+{
+       unsigned long ret[PLPAR_HCALL_BUFSIZE];
+       uint64_t rc, token;
+
+       token = 0;
+
+       /* NB: unbind has the same retry requirements mentioned above */
+       do {
+               rc = plpar_hcall(H_SCM_UNBIND_MEM, ret, p->drc_index,
+                               p->bound_addr, p->blocks, token);
+               token = be64_to_cpu(ret);

...same busy loop comment.

+       } while (rc == H_BUSY);
+
+       if (rc)
+               dev_err(&p->pdev->dev, "unbind error: %lld\n", rc);
+
+       return !!rc;
+}
+
+static int papr_scm_meta_get(struct papr_scm_priv *p,
+                       struct nd_cmd_get_config_data_hdr *hdr)
+{
+       unsigned long data[PLPAR_HCALL_BUFSIZE];
+       int64_t ret;
+
+       if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
+               return -EINVAL;
+
+       ret = plpar_hcall(H_SCM_READ_METADATA, data, p->drc_index,
+                       hdr->in_offset, 1);
+
+       if (ret == H_PARAMETER) /* bad DRC index */
+               return -ENODEV;
+       if (ret)
+               return -EINVAL; /* other invalid parameter */
+
+       hdr->out_buf[0] = data[0] & 0xff;
+
+       return 0;
+}
+
+static int papr_scm_meta_set(struct papr_scm_priv *p,
+                       struct nd_cmd_set_config_hdr *hdr)
+{
+       int64_t ret;
+
+       if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
+               return -EINVAL;
+
+       ret = plpar_hcall_norets(H_SCM_WRITE_METADATA,
+                       p->drc_index, hdr->in_offset, hdr->in_buf[0], 1);
+
+       if (ret == H_PARAMETER) /* bad DRC index */
+               return -ENODEV;
+       if (ret)
+               return -EINVAL; /* other invalid parameter */
+
+       return 0;
+}
+
+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;
+
+       /* Only dimm-specific calls are supported atm */
+       if (!nvdimm)
+               return -EINVAL;
+
+       p = nvdimm_provider_data(nvdimm);
+
+       switch (cmd) {
+       case ND_CMD_GET_CONFIG_SIZE:
+               get_size_hdr = buf;
+
+               get_size_hdr->status = 0;
+               get_size_hdr->max_xfer = 1;
+               get_size_hdr->config_size = p->metadata_size;
+               *cmd_rc = 0;
+               break;
+
+       case ND_CMD_GET_CONFIG_DATA:
+               *cmd_rc = papr_scm_meta_get(p, buf);
+               break;
+
+       case ND_CMD_SET_CONFIG_DATA:
+               *cmd_rc = papr_scm_meta_set(p, buf);
+               break;
+
+       default:
+               return -EINVAL;
+       }
+
+       dev_dbg(&p->pdev->dev, "returned with cmd_rc = %d\n", *cmd_rc);
+
+       return 0;
+}
+
+static const struct attribute_group *region_attr_groups[] = {
+       &nd_region_attribute_group,
+       &nd_device_attribute_group,
+       &nd_mapping_attribute_group,
+       &nd_numa_attribute_group,
+       NULL,
+};
+
+static const struct attribute_group *bus_attr_groups[] = {
+       &nvdimm_bus_attribute_group,
+       NULL,
+};
+
+static const struct attribute_group *papr_scm_dimm_groups[] = {
+       &nvdimm_attribute_group,
+       &nd_device_attribute_group,
+       NULL,
+};
+
+static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
+{
+       struct device *dev = &p->pdev->dev;
+       struct nd_mapping_desc mapping;
+       struct nd_region_desc ndr_desc;
+       unsigned long dimm_flags;
+
+       p->bus_desc.ndctl = papr_scm_ndctl;
+       p->bus_desc.module = THIS_MODULE;
+       p->bus_desc.of_node = p->pdev->dev.of_node;
+       p->bus_desc.attr_groups = bus_attr_groups;
+       p->bus_desc.provider_name = kstrdup(p->pdev->name, GFP_KERNEL);
+
+       if (!p->bus_desc.provider_name)
+               return -ENOMEM;
+
+       p->bus = nvdimm_bus_register(NULL, &p->bus_desc);
+       if (!p->bus) {
+               dev_err(dev, "Error creating nvdimm bus %pOF\n", p->dn);
+               return -ENXIO;
+       }
+
+       dimm_flags = 0;
+       set_bit(NDD_ALIASING, &dimm_flags);
+
+       p->nvdimm = nvdimm_create(p->bus, p, papr_scm_dimm_groups,
+                               dimm_flags, PAPR_SCM_DIMM_CMD_MASK, 0, NULL);

Looks good, although I'm just about to push out commits that change
this function signature to take a 'security_ops' pointer. If you need
a stable branch to base this on, let me know.

+       if (!p->nvdimm) {
+               dev_err(dev, "Error creating DIMM object for %pOF\n", p->dn);
+               goto err;
+       }
+
+       /* now add the region */
+
+       memset(&mapping, 0, sizeof(mapping));
+       mapping.nvdimm = p->nvdimm;
+       mapping.start = p->res.start;
+       mapping.size = p->blocks * p->block_size; // XXX: potential overflow?

Ideally, should be nvdimm relative addresses. Since you have just a
single DIMM per-region I would expect this to be 0 to
nvdimm->region_size. That said I don't think anything breaks if you
make the nvdimm address equal to the system-physical address, just
wanted to point out the intent. This only matters when you have
multiple DIMMs per region and need to record the per-DIMM contribution
in the labels on each DIMM.

Other than that looks ok to me:

Acked-by: Dan Williams <redacted>

...just the matter of what to do about function signature change.