Jonathan Cameron wrote:
> On Thu, 23 Jun 2022 21:19:44 -0700
> Dan Williams <[email protected]> wrote:
>
> > CXL regions (interleave sets) are made up of a set of memory devices
> > where each device maps a portion of the interleave with one of its
> > decoders (see CXL 2.0 8.2.5.12 CXL HDM Decoder Capability Structure).
> > As endpoint decoders are identified by a provisioning tool they can be
> > added to a region provided the region interleave properties are set
> > (way, granularity, HPA) and DPA has been assigned to the decoder.
> >
> > The attach event triggers several validation checks, for example:
> > - is the DPA sized appropriately for the region
> > - is the decoder reachable via the host-bridges identified by the
> > region's root decoder
> > - is the device already active in a different region position slot
> > - are there already regions with a higher HPA active on a given port
> > (per CXL 2.0 8.2.5.12.20 Committing Decoder Programming)
> >
> > ...and the attach event affords an opportunity to collect data and
> > resources relevant to later programming the target lists in switch
> > decoders, for example:
> > - allocate a decoder at each cxl_port in the decode chain
> > - for a given switch port, how many the region's endpoints are hosted
> > through the port
> > - how many unique targets (next hops) does a port need to map to reach
> > those endpoints
> >
> > The act of reconciling this information and deploying it to the decoder
> > configuration is saved for a follow-on patch.
> >
> > Co-developed-by: Ben Widawsky <[email protected]>
> > Signed-off-by: Ben Widawsky <[email protected]>
> > Signed-off-by: Dan Williams <[email protected]>
> > ---
> > drivers/cxl/core/core.h | 7 +
> > drivers/cxl/core/port.c | 10 +-
> > drivers/cxl/core/region.c | 338 +++++++++++++++++++++++++++++++++++++-
> > drivers/cxl/cxl.h | 20 +++
> > drivers/cxl/cxlmem.h | 5 +
> > 5 files changed, 372 insertions(+), 8 deletions(-)
> >
>
>
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index 4830365f3857..65bf84abad57 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -428,6 +428,254 @@ static size_t show_targetN(struct cxl_region *cxlr,
> > char *buf, int pos)
> > return rc;
> > }
> >
>
> > +
> > +static struct cxl_region_ref *alloc_region_ref(struct cxl_port *port,
> > + struct cxl_region *cxlr)
> > +{
> > + struct cxl_region_ref *cxl_rr;
> > +
> > + cxl_rr = kzalloc(sizeof(*cxl_rr), GFP_KERNEL);
> > + if (!cxl_rr)
> > + return NULL;
> > + cxl_rr->port = port;
> > + cxl_rr->region = cxlr;
> > + xa_init(&cxl_rr->endpoints);
> > + return cxl_rr;
> > +}
> > +
> > +static void free_region_ref(struct cxl_region_ref *cxl_rr)
> > +{
> > + struct cxl_port *port = cxl_rr->port;
> > + struct cxl_region *cxlr = cxl_rr->region;
> > + struct cxl_decoder *cxld = cxl_rr->decoder;
> > +
> > + dev_WARN_ONCE(&cxlr->dev, cxld->region != cxlr, "region mismatch\n");
> > + if (cxld->region == cxlr) {
> > + cxld->region = NULL;
> > + put_device(&cxlr->dev);
> > + }
> > +
> > + xa_erase(&port->regions, (unsigned long)cxlr);
>
> Why do we have things in a free_ function that aren't simply removing things
> created in the alloc()? I'd kind of expect this to be in a cxl_rr_del() or
> similar.
Fixed it the other way by just open-coding cxl_rr_add() into
alloc_region_ref(). There was no good reason to have them as separate
steps.
>
> > + xa_destroy(&cxl_rr->endpoints);
> > + kfree(cxl_rr);
> > +}
> > +
> > +static int cxl_rr_add(struct cxl_region_ref *cxl_rr)
> > +{
> > + struct cxl_port *port = cxl_rr->port;
> > + struct cxl_region *cxlr = cxl_rr->region;
> > +
> > + return xa_insert(&port->regions, (unsigned long)cxlr, cxl_rr,
> > + GFP_KERNEL);
> > +}
> > +
> > +static int cxl_rr_ep_add(struct cxl_region_ref *cxl_rr,
> > + struct cxl_endpoint_decoder *cxled)
> > +{
> > + int rc;
> > + struct cxl_port *port = cxl_rr->port;
> > + struct cxl_region *cxlr = cxl_rr->region;
> > + struct cxl_decoder *cxld = cxl_rr->decoder;
> > + struct cxl_ep *ep = cxl_ep_load(port, cxled_to_memdev(cxled));
> > +
> > + rc = xa_insert(&cxl_rr->endpoints, (unsigned long)cxled, ep,
> > + GFP_KERNEL);
> > + if (rc)
> > + return rc;
> > + cxl_rr->nr_eps++;
> > +
> > + if (!cxld->region) {
> > + cxld->region = cxlr;
> > + get_device(&cxlr->dev);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int cxl_port_attach_region(struct cxl_port *port,
> > + struct cxl_region *cxlr,
> > + struct cxl_endpoint_decoder *cxled, int pos)
> > +{
> > + struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> > + struct cxl_ep *ep = cxl_ep_load(port, cxlmd);
> > + struct cxl_region_ref *cxl_rr = NULL, *iter;
> > + struct cxl_region_params *p = &cxlr->params;
> > + struct cxl_decoder *cxld = NULL;
> > + unsigned long index;
> > + int rc = -EBUSY;
> > +
> > + lockdep_assert_held_write(&cxl_region_rwsem);
>
> This function is complex enough that maybe it would benefit from
> some saying what each part is doing.
...added a kdoc block:
/**
* cxl_port_attach_region() - track a region's interest in a port by endpoint
* @port: port to add a new region reference 'struct cxl_region_ref'
* @cxlr: region to attach to @port
* @cxled: endpoint decoder used to create or further pin a region reference
* @pos: interleave position of @cxled in @cxlr
*
* The attach event is an opportunity to validate CXL decode setup
* constraints and record metadata needed for programming HDM decoders,
* in particular decoder target lists.
*
* The steps are:
* - validate that there are no other regions with a higher HPA already
* associated with @port
* - establish a region reference if one is not already present
* - additionally allocate a decoder instance that will host @cxlr on
* @port
* - pin the region reference by the endpoint
* - account for how many entries in @port's target list are needed to
* cover all of the added endpoints.
*/
>
> > +
> > + xa_for_each(&port->regions, index, iter) {
> > + struct cxl_region_params *ip = &iter->region->params;
> > +
> > + if (iter->region == cxlr)
> > + cxl_rr = iter;
> > + if (ip->res->start > p->res->start) {
> > + dev_dbg(&cxlr->dev,
> > + "%s: HPA order violation %s:%pr vs %pr\n",
> > + dev_name(&port->dev),
> > + dev_name(&iter->region->dev), ip->res, p->res);
> > + return -EBUSY;
> > + }
> > + }
> > +
> > + if (cxl_rr) {
> > + struct cxl_ep *ep_iter;
> > + int found = 0;
> > +
> > + cxld = cxl_rr->decoder;
> > + xa_for_each(&cxl_rr->endpoints, index, ep_iter) {
> > + if (ep_iter == ep)
> > + continue;
> > + if (ep_iter->next == ep->next) {
> > + found++;
> > + break;
> > + }
> > + }
> > +
> > + /*
> > + * If this is a new target or if this port is direct connected
> > + * to this endpoint then add to the target count.
> > + */
> > + if (!found || !ep->next)
> > + cxl_rr->nr_targets++;
> > + } else {
> > + cxl_rr = alloc_region_ref(port, cxlr);
> > + if (!cxl_rr) {
> > + dev_dbg(&cxlr->dev,
> > + "%s: failed to allocate region reference\n",
> > + dev_name(&port->dev));
> > + return -ENOMEM;
> > + }
> > + rc = cxl_rr_add(cxl_rr);
> > + if (rc) {
> > + dev_dbg(&cxlr->dev,
> > + "%s: failed to track region reference\n",
> > + dev_name(&port->dev));
> > + kfree(cxl_rr);
> > + return rc;
> > + }
> > + }
> > +
> > + if (!cxld) {
> > + if (port == cxled_to_port(cxled))
> > + cxld = &cxled->cxld;
> > + else
> > + cxld = cxl_region_find_decoder(port, cxlr);
> > + if (!cxld) {
> > + dev_dbg(&cxlr->dev, "%s: no decoder available\n",
> > + dev_name(&port->dev));
> > + goto out_erase;
> > + }
> > +
> > + if (cxld->region) {
> > + dev_dbg(&cxlr->dev, "%s: %s already attached to %s\n",
> > + dev_name(&port->dev), dev_name(&cxld->dev),
> > + dev_name(&cxld->region->dev));
> > + rc = -EBUSY;
> > + goto out_erase;
> > + }
> > +
> > + cxl_rr->decoder = cxld;
> > + }
> > +
> > + rc = cxl_rr_ep_add(cxl_rr, cxled);
> > + if (rc) {
> > + dev_dbg(&cxlr->dev,
> > + "%s: failed to track endpoint %s:%s reference\n",
> > + dev_name(&port->dev), dev_name(&cxlmd->dev),
> > + dev_name(&cxld->dev));
> > + goto out_erase;
> > + }
> > +
> > + return 0;
> > +out_erase:
> > + if (cxl_rr->nr_eps == 0)
> > + free_region_ref(cxl_rr);
> > + return rc;
> > +}
> > +
>
> >
> > static void cxl_region_detach(struct cxl_endpoint_decoder *cxled)
> > {
> > + struct cxl_port *iter, *ep_port = cxled_to_port(cxled);
> > struct cxl_region *cxlr = cxled->cxld.region;
> > struct cxl_region_params *p;
> >
> > @@ -481,6 +811,10 @@ static void cxl_region_detach(struct
> > cxl_endpoint_decoder *cxled)
> > p = &cxlr->params;
> > get_device(&cxlr->dev);
> >
> > + for (iter = ep_port; !is_cxl_root(iter);
> > + iter = to_cxl_port(iter->dev.parent))
> > + cxl_port_detach_region(iter, cxlr, cxled);
> > +
> > if (cxled->pos < 0 || cxled->pos >= p->interleave_ways ||
> > p->targets[cxled->pos] != cxled) {
> > struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> > @@ -491,6 +825,8 @@ static void cxl_region_detach(struct
> > cxl_endpoint_decoder *cxled)
> > goto out;
> > }
> >
> > + if (p->state == CXL_CONFIG_ACTIVE)
>
> I 'think' the state is either CXL_CONFIG_ACTIVE or
> CXL_CONFIG_INTERLEAVE_ACTIVE,
> so you could set this unconditionally. A comment here on permissible
> states would be useful for future reference.
cxl_region_detach() should not care if the region state is idle. Not
that it will happen in the current code, but the only expectation is
that if the region is active and a endpoint departs it must be
downgraded in config state. CXL_CONFIG_IDLE is permissible, although not
expected. I do not think a comment is needed if the "if (p->state ==
CXL_CONFIG_ACTIVE)" check stays.
>
> > + p->state = CXL_CONFIG_INTERLEAVE_ACTIVE;
> > p->targets[cxled->pos] = NULL;
> > p->nr_targets--;
>
>
