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Before determining how much DPA to >> allocate the amount of available HPA must be determined. Also, not all >> HPA is created equal, some specifically targets RAM, some target PMEM, >> some is prepared for device-memory flows like HDM-D and HDM-DB, and some >> is host-only (HDM-H). >> >> Wrap all of those concerns into an API that retrieves a root decoder >> (platform CXL window) that fits the specified constraints and the >> capacity available for a new region. >> >> Based on https://lore.kernel.org/linux-cxl/168592159290.1948938.13522227102445462976.stgit@dwillia2-xfh.jf.intel.com/ >> >> Signed-off-by: Alejandro Lucero >> Co-developed-by: Dan Williams > A couple of trivial things inline. > > With those tidied up. > > Reviewed-by: Jonathan Cameron > >> --- >> drivers/cxl/core/region.c | 155 ++++++++++++++++++++++++++++++++++++++ >> drivers/cxl/cxl.h | 3 + >> include/cxl/cxl.h | 8 ++ >> 3 files changed, 166 insertions(+) >> >> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c >> index 967132b49832..239fe49bf6a6 100644 >> --- a/drivers/cxl/core/region.c >> +++ b/drivers/cxl/core/region.c >> @@ -687,6 +687,161 @@ static int free_hpa(struct cxl_region *cxlr) >> return 0; >> } >> >> +struct cxlrd_max_context { >> + struct device *host_bridge; >> + unsigned long flags; >> + resource_size_t max_hpa; >> + struct cxl_root_decoder *cxlrd; >> +}; >> + >> +static int find_max_hpa(struct device *dev, void *data) >> +{ >> + struct cxlrd_max_context *ctx = data; >> + struct cxl_switch_decoder *cxlsd; >> + struct cxl_root_decoder *cxlrd; >> + struct resource *res, *prev; >> + struct cxl_decoder *cxld; >> + resource_size_t max; >> + >> + if (!is_root_decoder(dev)) >> + return 0; >> + >> + cxlrd = to_cxl_root_decoder(dev); >> + cxlsd = &cxlrd->cxlsd; >> + cxld = &cxlsd->cxld; >> + if ((cxld->flags & ctx->flags) != ctx->flags) { >> + dev_dbg(dev, "%s, flags not matching: %08lx vs %08lx\n", >> + __func__, cxld->flags, ctx->flags); > Another __func__ to drop. > Check for other cases where dynamic debug applies. > I'll do. > >> + >> +/** >> + * cxl_get_hpa_freespace - find a root decoder with free capacity per constraints >> + * @cxlmd: the CXL memory device with an endpoint that is mapped by the returned >> + * decoder >> + * @flags: CXL_DECODER_F flags for selecting RAM vs PMEM, and HDM-H vs HDM-D[B] >> + * @max_avail_contig: output parameter of max contiguous bytes available in the >> + * returned decoder >> + * >> + * The return tuple of a 'struct cxl_root_decoder' and 'bytes available given >> + * in (@max_avail_contig))' is a point in time snapshot. If by the time the >> + * caller goes to use this root decoder's capacity the capacity is reduced then >> + * caller needs to loop and retry. >> + * >> + * The returned root decoder has an elevated reference count that needs to be >> + * put with put_device(cxlrd_dev(cxlrd)). Locking context is with > put_device(CXLRD_DEV(cxlrd)) Right. This helps to see the reference to cxl_acquire/release_endpoint needs to be dropped. Thanks! >> + * cxl_{acquire,release}_endpoint(), that ensures removal of the root decoder >> + * does not race. >> + */ >> +struct cxl_root_decoder *cxl_get_hpa_freespace(struct cxl_memdev *cxlmd, >> + unsigned long flags, >> + resource_size_t *max_avail_contig) >> +{ >> + struct cxl_port *endpoint = cxlmd->endpoint; >> + struct cxlrd_max_context ctx = { >> + .host_bridge = endpoint->host_bridge, >> + .flags = flags, >> + }; >> + struct cxl_port *root_port; >> + struct cxl_root *root __free(put_cxl_root) = find_cxl_root(endpoint); >> + >> + if (!is_cxl_endpoint(endpoint)) { >> + dev_dbg(&endpoint->dev, "hpa requestor is not an endpoint\n"); >> + return ERR_PTR(-EINVAL); >> + } >> + >> + if (!root) { >> + dev_dbg(&endpoint->dev, "endpoint can not be related to a root port\n"); >> + return ERR_PTR(-ENXIO); >> + } >> + >> + root_port = &root->port; >> + down_read(&cxl_region_rwsem); >> + device_for_each_child(&root_port->dev, &ctx, find_max_hpa); >> + up_read(&cxl_region_rwsem); >> + >> + if (!ctx.cxlrd) >> + return ERR_PTR(-ENOMEM); >> + >> + *max_avail_contig = ctx.max_hpa; >> + return ctx.cxlrd; >> +} >> +EXPORT_SYMBOL_NS_GPL(cxl_get_hpa_freespace, "CXL"); >> +