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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 HPA targets RAM, some >> targets PMEM, some is prepared for device-memory flows like HDM-D and HDM-DB, >> and some is HDM-H (host-only). >> >> In order to support Type2 CXL devices, 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. >> >> Add a complementary function for releasing the reference to such root >> decoder. >> >> Based on https://lore.kernel.org/linux-cxl/168592159290.1948938.13522227102445462976.stgit@dwillia2-xfh.jf.intel.com/ >> >> Signed-off-by: Alejandro Lucero >> Reviewed-by: Jonathan Cameron > One thing I noticed on a fresh read through... > >> --- >> drivers/cxl/core/region.c | 162 ++++++++++++++++++++++++++++++++++++++ >> drivers/cxl/cxl.h | 3 + >> include/cxl/cxl.h | 6 ++ >> 3 files changed, 171 insertions(+) >> >> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c >> index e9bf42d91689..c5b66204ecde 100644 >> --- a/drivers/cxl/core/region.c >> +++ b/drivers/cxl/core/region.c >> @@ -703,6 +703,168 @@ static int free_hpa(struct cxl_region *cxlr) >> return 0; >> } >> >> +struct cxlrd_max_context { >> + struct device * const *host_bridges; >> + int interleave_ways; >> + 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; >> + int found = 0; >> + >> + 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, "flags not matching: %08lx vs %08lx\n", >> + cxld->flags, ctx->flags); >> + return 0; >> + } >> + >> + for (int i = 0; i < ctx->interleave_ways; i++) { > I think ctx->interleave_ways == 0 as it's never set, so found is never > set, but then the check below succeeds as found == 0 and ctx->interleave_ways == 0 > > Definitely doesn't feel intentional! Yes, that is the consequence of the other thing you spotted later. > >> + for (int j = 0; j < ctx->interleave_ways; j++) { >> + if (ctx->host_bridges[i] == cxlsd->target[j]->dport_dev) { >> + found++; >> + break; >> + } >> + } >> + } >> + >> + if (found != ctx->interleave_ways) { >> + dev_dbg(dev, >> + "Not enough host bridges. Found %d for %d interleave ways requested\n", >> + found, ctx->interleave_ways); >> + return 0; >> + } >> +} >> + >> +/** >> + * cxl_get_hpa_freespace - find a root decoder with free capacity per constraints >> + * @cxlmd: the mem device requiring the HPA >> + * @interleave_ways: number of entries in @host_bridges >> + * @flags: CXL_DECODER_F flags for selecting RAM vs PMEM, and Type2 device >> + * @max_avail_contig: output parameter of max contiguous bytes available in the >> + * returned decoder >> + * >> + * Returns a pointer to a struct cxl_root_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 decoder and its 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 cxl_put_root_decoder(cxlrd). >> + */ >> +struct cxl_root_decoder *cxl_get_hpa_freespace(struct cxl_memdev *cxlmd, >> + int interleave_ways, > Currently unused. I think you mean to set the field in ctx Right. Refactoring went wrong. I'll fix it. Thanks! > >> + unsigned long flags, >> + resource_size_t *max_avail_contig) >> +{ >> + struct cxl_port *endpoint = cxlmd->endpoint; >> + struct cxlrd_max_context ctx = { >> + .flags = flags, >> + }; >> + struct cxl_port *root_port; >> + >> + if (!endpoint) { >> + dev_dbg(&cxlmd->dev, "endpoint not linked to memdev\n"); >> + return ERR_PTR(-ENXIO); >> + } >> + >> + ctx.host_bridges = &endpoint->host_bridge; >> + >> + struct cxl_root *root __free(put_cxl_root) = find_cxl_root(endpoint); >> + if (!root) { >> + dev_dbg(&endpoint->dev, "endpoint is not related to a root port\n"); >> + return ERR_PTR(-ENXIO); >> + } >> + >> + root_port = &root->port; >> + scoped_guard(rwsem_read, &cxl_rwsem.region) >> + device_for_each_child(&root_port->dev, &ctx, find_max_hpa); >> + >> + 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");