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Given the HPA >> capacity constraint, define an API, cxl_request_dpa(), that has the >> flexibility to map the minimum amount of memory the driver needs to > Bonus space before map. Ok. >> operate vs the total possible that can be mapped given HPA availability. >> >> Factor out the core of cxl_dpa_alloc, that does free space scanning, >> into a cxl_dpa_freespace() helper, and use that to balance the capacity >> available to map vs the @min and @max arguments to cxl_request_dpa. >> >> Based on https://lore.kernel.org/linux-cxl/168592158743.1948938.7622563891193802610.stgit@dwillia2-xfh.jf.intel.com/ >> >> Signed-off-by: Alejandro Lucero >> Co-developed-by: Dan Williams > Comments inline. > >> --- >> drivers/cxl/core/hdm.c | 154 +++++++++++++++++++++++++++++++++++------ >> include/cxl/cxl.h | 5 ++ >> 2 files changed, 138 insertions(+), 21 deletions(-) >> >> +int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size) >> +{ >> + struct cxl_port *port = cxled_to_port(cxled); >> + struct device *dev = &cxled->cxld.dev; >> + resource_size_t start, avail, skip; >> + int rc; >> + >> + down_write(&cxl_dpa_rwsem); >> + if (cxled->cxld.region) { >> + dev_dbg(dev, "EBUSY, decoder attached to %s\n", >> + dev_name(&cxled->cxld.region->dev)); >> + rc = -EBUSY; >> + goto out; >> + } >> + >> + if (cxled->cxld.flags & CXL_DECODER_F_ENABLE) { >> + dev_dbg(dev, "EBUSY, decoder enabled\n"); >> + rc = -EBUSY; >> goto out; >> } >> >> + avail = cxl_dpa_freespace(cxled, &start, &skip); >> + >> if (size > avail) { >> dev_dbg(dev, "%pa exceeds available %s capacity: %pa\n", &size, >> - cxl_decoder_mode_name(cxled->mode), &avail); >> + cxled->mode == CXL_DECODER_RAM ? "ram" : "pmem", > This is reverting an earlier change. I guess accidental? Yes, I should be using the function. >> + &avail); >> rc = -ENOSPC; >> goto out; >> } >> @@ -538,6 +557,99 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size) >> return devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled); >> } >> +/** >> + * cxl_request_dpa - search and reserve DPA given input constraints >> + * @cxlmd: memdev with an endpoint port with available decoders >> + * @is_ram: DPA operation mode (ram vs pmem) >> + * @min: the minimum amount of capacity the call needs >> + * @max: extra capacity to allocate after min is satisfied > Includes the extra capacity. Otherwise capacity allocated as documented > is min + max which seems unlikely. Right. I'll fix it. >> + * >> + * Given that a region needs to allocate from limited HPA capacity it >> + * may be the case that a device has more mappable DPA capacity than >> + * available HPA. So, the expectation is that @min is a driver known >> + * value for how much capacity is needed, and @max is based the limit of >> + * how much HPA space is available for a new region. >> + * >> + * Returns a pinned cxl_decoder with at least @min bytes of capacity >> + * reserved, or an error pointer. The caller is also expected to own the >> + * lifetime of the memdev registration associated with the endpoint to >> + * pin the decoder registered as well. >> + */ >> +struct cxl_endpoint_decoder *cxl_request_dpa(struct cxl_memdev *cxlmd, >> + bool is_ram, >> + resource_size_t min, >> + resource_size_t max) >> +{ >> + struct cxl_port *endpoint = cxlmd->endpoint; >> + struct cxl_endpoint_decoder *cxled; >> + enum cxl_decoder_mode mode; >> + struct device *cxled_dev; >> + resource_size_t alloc; >> + int rc; >> + >> + if (!IS_ALIGNED(min | max, SZ_256M)) >> + return ERR_PTR(-EINVAL); >> + >> + down_read(&cxl_dpa_rwsem); >> + cxled_dev = device_find_child(&endpoint->dev, NULL, find_free_decoder); >> + up_read(&cxl_dpa_rwsem); >> + >> + if (!cxled_dev) >> + cxled = ERR_PTR(-ENXIO); > if (!cxled_dev) > return ERR_PTR(-ENXIO); > > cxled = to... > if (!cxled) //assuming this has any way to fail in which > case I think you would need to put the device... > put_device(cxled_dev); > return NULL; > > Though do you actualy want to return an error in this case? This handling makes the code clearer, and yes, you are right about the put_device. I'll fix it. >> + else >> + cxled = to_cxl_endpoint_decoder(cxled_dev); >> + >> + if (!cxled || IS_ERR(cxled)) >> + return cxled; > Drop this with changes above. Sure. Thanks! > >> + >> + if (is_ram) >> + mode = CXL_DECODER_RAM; >> + else >> + mode = CXL_DECODER_PMEM; >> + >> + rc = cxl_dpa_set_mode(cxled, mode); >> + if (rc) >> + goto err; >> + >> + down_read(&cxl_dpa_rwsem); >> + alloc = cxl_dpa_freespace(cxled, NULL, NULL); >> + up_read(&cxl_dpa_rwsem); >> + >> + if (max) >> + alloc = min(max, alloc); >> + if (alloc < min) { >> + rc = -ENOMEM; >> + goto err; >> + } >> + >> + rc = cxl_dpa_alloc(cxled, alloc); >> + if (rc) >> + goto err; >> + >> + return cxled; >> +err: >> + put_device(cxled_dev); >> + return ERR_PTR(rc); >> +} >> +EXPORT_SYMBOL_NS_GPL(cxl_request_dpa, "CXL");