On Mon, 07 Oct 2024 18:16:31 -0500 ira.weiny@xxxxxxxxx wrote: > From: Navneet Singh <navneet.singh@xxxxxxxxx> > > Dynamic capacity device extents may be left in an accepted state on a > device due to an unexpected host crash. In this case it is expected > that the creation of a new region on top of a DC partition can read > those extents and surface them for continued use. > > Once all endpoint decoders are part of a region and the region is being > realized, a read of the 'devices extent list' can reveal these > previously accepted extents. > > CXL r3.1 specifies the mailbox call Get Dynamic Capacity Extent List for > this purpose. The call returns all the extents for all dynamic capacity > partitions. If the fabric manager is adding extents to any DCD > partition, the extent list for the recovered region may change. In this > case the query must retry. Upon retry the query could encounter extents > which were accepted on a previous list query. Adding such extents is > ignored without error because they are entirely within a previous > accepted extent. > > The scan for existing extents races with the dax_cxl driver. This is > synchronized through the region device lock. Extents which are found > after the driver has loaded will surface through the normal notification > path while extents seen prior to the driver are read during driver load. > > Signed-off-by: Navneet Singh <navneet.singh@xxxxxxxxx> > Co-developed-by: Ira Weiny <ira.weiny@xxxxxxxxx> > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> > One buglet, and a request for an error message. With those. Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c > index d66beec687a0..6b25d15403a3 100644 > --- a/drivers/cxl/core/mbox.c > +++ b/drivers/cxl/core/mbox.c > @@ -1697,6 +1697,111 @@ int cxl_dev_dynamic_capacity_identify(struct cxl_memdev_state *mds) > } > EXPORT_SYMBOL_NS_GPL(cxl_dev_dynamic_capacity_identify, CXL); > > +/* Return -EAGAIN if the extent list changes while reading */ > +static int __cxl_process_extent_list(struct cxl_endpoint_decoder *cxled) > +{ > + u32 current_index, total_read, total_expected, initial_gen_num; > + struct cxl_memdev_state *mds = cxled_to_mds(cxled); > + struct cxl_mailbox *cxl_mbox = &mds->cxlds.cxl_mbox; > + struct device *dev = mds->cxlds.dev; > + struct cxl_mbox_cmd mbox_cmd; > + u32 max_extent_count; > + bool first = true; > + > + struct cxl_mbox_get_extent_out *extents __free(kfree) = __free(kvfree) > + kvmalloc(cxl_mbox->payload_size, GFP_KERNEL); > + if (!extents) > + return -ENOMEM; ... > +} > static void cxlr_dax_unregister(void *_cxlr_dax) > { > struct cxl_dax_region *cxlr_dax = _cxlr_dax; > @@ -3224,6 +3233,9 @@ static int devm_cxl_add_dax_region(struct cxl_region *cxlr) > dev_dbg(&cxlr->dev, "%s: register %s\n", dev_name(dev->parent), > dev_name(dev)); > > + if (cxlr->mode == CXL_REGION_DC) > + cxlr_add_existing_extents(cxlr); Whilst there isn't a whole lot we can do if this fails, I'd like an error print to indicate something odd is going on. Probably pass any error up to here then print a message before carrying on. > + > return devm_add_action_or_reset(&cxlr->dev, cxlr_dax_unregister, > cxlr_dax); > err: