Re: [PATCH v3 18/25] cxl/extent: Process DCD events and realize region extents

Ira Weiny
2024-08-29T21:17:00Z

Jonathan Cameron wrote:
> On Fri, 16 Aug 2024 09:44:26 -0500
> ira.weiny@intel.com wrote:
>
> > From: Navneet Singh <navneet.singh@intel.com>
> >

[snip]

> > +static int match_contains(struct device *dev, void *data)
> > +{
> > + struct region_extent *region_extent = to_region_extent(dev);
> > + struct match_data *md = data;
> > + struct cxled_extent *entry;
> > + unsigned long index;
> > +
> > + if (!region_extent)
> > + return 0;
> > +
> > + xa_for_each(&region_extent->decoder_extents, index, entry) {
> > + if (md->cxled == entry->cxled &&
> > + range_contains(&entry->dpa_range, md->new_range))
> > + return true;
> As below, this returns int, so shouldn't be true or false.

Yep. Thanks.

>
> > + }
> > + return false;
> > +}
>
> > +static int match_overlaps(struct device *dev, void *data)
> > +{
> > + struct region_extent *region_extent = to_region_extent(dev);
> > + struct match_data *md = data;
> > + struct cxled_extent *entry;
> > + unsigned long index;
> > +
> > + if (!region_extent)
> > + return 0;
> > +
> > + xa_for_each(&region_extent->decoder_extents, index, entry) {
> > + if (md->cxled == entry->cxled &&
> > + range_overlaps(&entry->dpa_range, md->new_range))
> > + return true;
>
> returns int, so returning true or false is odd.

Yep.

>
> > + }
> > +
> > + return false;
> > +}
>
>
> > +int cxl_rm_extent(struct cxl_memdev_state *mds, struct cxl_extent *extent)
> > +{
> > + u64 start_dpa = le64_to_cpu(extent->start_dpa);
> > + struct cxl_memdev *cxlmd = mds->cxlds.cxlmd;
> > + struct cxl_endpoint_decoder *cxled;
> > + struct range hpa_range, dpa_range;
> > + struct cxl_region *cxlr;
> > +
> > + dpa_range = (struct range) {
> > + .start = start_dpa,
> > + .end = start_dpa + le64_to_cpu(extent->length) - 1,
> > + };
> > +
> > + guard(rwsem_read)(&cxl_region_rwsem);
> > + cxlr = cxl_dpa_to_region(cxlmd, start_dpa, &cxled);
> > + if (!cxlr) {
> > + memdev_release_extent(mds, &dpa_range);
>
> How does this condition happen? Perhaps a comment needed.

Fair enough. Proposed comment.

/*
* No region can happen here for a few reasons:
*
* 1) Extents were accepted and the host crashed/rebooted
* leaving them in an accepted state. On reboot the host
* has not yet created a region to own them.
*
* 2) Region destruction won the race with the device releasing
* all the extents. Here the release will be a duplicate of
* the one sent via region destruction.
*
* 3) The device is confused and releasing extents for which no
* region ever existed.
*
* In all these cases make sure the device knows we are not
* using this extent.
*/

Item 2 is AFAICS ok with the spec.

>
> > + return -ENXIO;
> > + }
> > +
> > + calc_hpa_range(cxled, cxlr->cxlr_dax, &dpa_range, &hpa_range);
> > +
> > + /* Remove region extents which overlap */
> > + return device_for_each_child(&cxlr->cxlr_dax->dev, &hpa_range,
> > + cxlr_rm_extent);
> > +}
> > +
> > +static int cxlr_add_extent(struct cxl_dax_region *cxlr_dax,
> > + struct cxl_endpoint_decoder *cxled,
> > + struct cxled_extent *ed_extent)
> > +{
> > + struct region_extent *region_extent;
> > + struct range hpa_range;
> > + int rc;
> > +
> > + calc_hpa_range(cxled, cxlr_dax, &ed_extent->dpa_range, &hpa_range);
> > +
> > + region_extent = alloc_region_extent(cxlr_dax, &hpa_range, ed_extent->tag);
> > + if (IS_ERR(region_extent))
> > + return PTR_ERR(region_extent);
> > +
> > + rc = xa_insert(&region_extent->decoder_extents, (unsigned long)ed_extent, ed_extent,
>
> I'd wrap that earlier to keep the line a bit shorter.

Done.

>
> > + GFP_KERNEL);
> > + if (rc) {
> > + free_region_extent(region_extent);
> > + return rc;
> > + }
> > +
> > + /* device model handles freeing region_extent */
> > + return online_region_extent(region_extent);
> > +}
> > +
> > +/* Callers are expected to ensure cxled has been attached to a region */
> > +int cxl_add_extent(struct cxl_memdev_state *mds, struct cxl_extent *extent)
> > +{
> > + u64 start_dpa = le64_to_cpu(extent->start_dpa);
> > + struct cxl_memdev *cxlmd = mds->cxlds.cxlmd;
> > + struct cxl_endpoint_decoder *cxled;
> > + struct range ed_range, ext_range;
> > + struct cxl_dax_region *cxlr_dax;
> > + struct cxled_extent *ed_extent;
> > + struct cxl_region *cxlr;
> > + struct device *dev;
> > +
> > + ext_range = (struct range) {
> > + .start = start_dpa,
> > + .end = start_dpa + le64_to_cpu(extent->length) - 1,
> > + };
> > +
> > + guard(rwsem_read)(&cxl_region_rwsem);
> > + cxlr = cxl_dpa_to_region(cxlmd, start_dpa, &cxled);
> > + if (!cxlr)
> > + return -ENXIO;
> > +
> > + cxlr_dax = cxled->cxld.region->cxlr_dax;
> > + dev = &cxled->cxld.dev;
> > + ed_range = (struct range) {
> > + .start = cxled->dpa_res->start,
> > + .end = cxled->dpa_res->end,
> > + };
> > +
> > + dev_dbg(&cxled->cxld.dev, "Checking ED (%pr) for extent %par\n",
> > + cxled->dpa_res, &ext_range);
> > +
> > + if (!range_contains(&ed_range, &ext_range)) {
> > + dev_err_ratelimited(dev,
> > + "DC extent DPA %par (%*phC) is not fully in ED %par\n",
> > + &ext_range.start, CXL_EXTENT_TAG_LEN,
> > + extent->tag, &ed_range);
> > + return -ENXIO;
> > + }
> > +
> > + if (extents_contain(cxlr_dax, cxled, &ext_range))
>
> This case confuses me. If the extents are already there I think we should
> error out or at least print something as that's very wrong.

I thought we discussed this in one of the community meetings that it would be
ok to accept these. We could certainly print a warning here.

In all honestly I'm wondering if these restrictions are really needed anymore.
But at the same time I really, really, really don't think anyone has a good use
case to have to support these cases. So I'm keeping the code simple for now.

>
> > + return 0;
> > +
> > + if (extents_overlap(cxlr_dax, cxled, &ext_range))
> > + return -ENXIO;
> > +
> > + ed_extent = kzalloc(sizeof(*ed_extent), GFP_KERNEL);
> > + if (!ed_extent)
> > + return -ENOMEM;
> > +
> > + ed_extent->cxled = cxled;
> > + ed_extent->dpa_range = ext_range;
> > + memcpy(ed_extent->tag, extent->tag, CXL_EXTENT_TAG_LEN);
> > +
> > + dev_dbg(dev, "Add extent %par (%*phC)\n", &ed_extent->dpa_range,
> > + CXL_EXTENT_TAG_LEN, ed_extent->tag);
> > +
> > + return cxlr_add_extent(cxlr_dax, cxled, ed_extent);
> > +}
> > diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> > index 01a447aaa1b1..f629ad7488ac 100644
> > --- a/drivers/cxl/core/mbox.c
> > +++ b/drivers/cxl/core/mbox.c
> > @@ -882,6 +882,48 @@ int cxl_enumerate_cmds(struct cxl_memdev_state *mds)
> > }
> > EXPORT_SYMBOL_NS_GPL(cxl_enumerate_cmds, CXL);
> >
> > +static int cxl_validate_extent(struct cxl_memdev_state *mds,
> > + struct cxl_extent *extent)
> > +{
> > + u64 start = le64_to_cpu(extent->start_dpa);
> > + u64 length = le64_to_cpu(extent->length);
> > + struct device *dev = mds->cxlds.dev;
> > +
> > + struct range ext_range = (struct range){
> > + .start = start,
> > + .end = start + length - 1,
> > + };
> > +
> > + if (le16_to_cpu(extent->shared_extn_seq) != 0) {
>
> That's not the 'main' way to tell if an extent is shared because
> we could have a single extent (so seq == 0).
> Should verify it's not in a DCD region that
> is shareable to make this decision.

Ah... :-/

>
> I've lost track on the region handling so maybe you already do
> this by not including those regions at all?

I don't think so.

I'll add the region check. I see now why I glossed over this though. The
shared nature of a DCD partition is defined in the DSMAS.

Is that correct? Or am I missing something in the spec?

>
> > + dev_err_ratelimited(dev,
> > + "DC extent DPA %par (%*phC) can not be shared\n",
> > + &ext_range.start, CXL_EXTENT_TAG_LEN,
> > + extent->tag);
> > + return -ENXIO;
> > + }
> > +
> > + /* Extents must not cross DC region boundary's */
> > + for (int i = 0; i < mds->nr_dc_region; i++) {
> > + struct cxl_dc_region_info *dcr = &mds->dc_region[i];
> > + struct range region_range = (struct range) {
> > + .start = dcr->base,
> > + .end = dcr->base + dcr->decode_len - 1,
> > + };
> > +
> > + if (range_contains(&region_range, &ext_range)) {
> > + dev_dbg(dev, "DC extent DPA %par (DCR:%d:%#llx)(%*phC)\n",
> > + &ext_range, i, start - dcr->base,
> > + CXL_EXTENT_TAG_LEN, extent->tag);
> > + return 0;
> > + }
> > + }
> > +
> > + dev_err_ratelimited(dev,
> > + "DC extent DPA %par (%*phC) is not in any DC region\n",
> > + &ext_range, CXL_EXTENT_TAG_LEN, extent->tag);
> > + return -ENXIO;
> > +}
> > +
> > void cxl_event_trace_record(const struct cxl_memdev *cxlmd,
> > enum cxl_event_log_type type,
> > enum cxl_event_type event_type,
> > @@ -1009,6 +1051,207 @@ static int cxl_clear_event_record(struct cxl_memdev_state *mds,
> > return rc;
> > }
> >
> > +static int cxl_send_dc_response(struct cxl_memdev_state *mds, int opcode,
> > + struct xarray *extent_array, int cnt)
> > +{
> > + struct cxl_mbox_dc_response *p;
> > + struct cxl_mbox_cmd mbox_cmd;
> > + struct cxl_extent *extent;
> > + unsigned long index;
> > + u32 pl_index;
> > + int rc = 0;
> > +
> > + size_t pl_size = struct_size(p, extent_list, cnt);
> > + u32 max_extents = cnt;
> > +
> What is cnt is zero? All extents rejected so none in the
> extent_array. Need to send a zero extent response to reject
> them all IIRC.

yes. I missed that thanks.

>
> > + /* May have to use more bit on response. */
> > + if (pl_size > mds->payload_size) {
> > + max_extents = (mds->payload_size - sizeof(*p)) /
> > + sizeof(struct updated_extent_list);
> > + pl_size = struct_size(p, extent_list, max_extents);
> > + }
> > +
> > + struct cxl_mbox_dc_response *response __free(kfree) =
> > + kzalloc(pl_size, GFP_KERNEL);
> > + if (!response)
> > + return -ENOMEM;
> > +
> > + pl_index = 0;
> > + xa_for_each(extent_array, index, extent) {
> > +
> > + response->extent_list[pl_index].dpa_start = extent->start_dpa;
> > + response->extent_list[pl_index].length = extent->length;
> > + pl_index++;
> > + response->extent_list_size = cpu_to_le32(pl_index);
> > +
> > + if (pl_index == max_extents) {
> > + mbox_cmd = (struct cxl_mbox_cmd) {
> > + .opcode = opcode,
> > + .size_in = struct_size(response, extent_list,
> > + pl_index),
> > + .payload_in = response,
> > + };
> > +
> > + response->flags = 0;
> > + if (pl_index < cnt)
> > + response->flags &= CXL_DCD_EVENT_MORE;
> > +
> > + rc = cxl_internal_send_cmd(mds, &mbox_cmd);
> > + if (rc)
> > + return rc;
> > + pl_index = 0;
> > + }
> > + }
> > +
> > + if (pl_index) {
> || !cnt
>
> I think so we send a nothing accepted message.

Yep.

>
> > + mbox_cmd = (struct cxl_mbox_cmd) {
> > + .opcode = opcode,
> > + .size_in = struct_size(response, extent_list,
> > + pl_index),
> > + .payload_in = response,
> > + };
> > +
> > + response->flags = 0;
> > + rc = cxl_internal_send_cmd(mds, &mbox_cmd);
> if (rc)
> return rc;
> > + }
> > +
>
> return 0; So that reader doesn't have to check what rc was in !pl_index
> case and avoids assigning rc right at the top.

Ah thanks. That might have been left over from something previous.

>
>
> > + return rc;
> > +}
>
>
> > +static int cxl_add_pending(struct cxl_memdev_state *mds)
> > +{
> > + struct device *dev = mds->cxlds.dev;
> > + struct cxl_extent *extent;
> > + unsigned long index;
> > + unsigned long cnt = 0;
> > + int rc;
> > +
> > + xa_for_each(&mds->pending_extents, index, extent) {
> > + if (validate_add_extent(mds, extent)) {
>
>
> Add a comment here that not accepting an extent but
> accepting some or none means this one was rejected (I'd forgotten how
> that bit worked)

Ok yeah that may not be clear without reading the spec closely.

/*
* Any extents which are to be rejected are omitted from
* the response. An empty response means all are
* rejected.
*/

>
> > + dev_dbg(dev, "unconsumed DC extent DPA:%#llx LEN:%#llx\n",
> > + le64_to_cpu(extent->start_dpa),
> > + le64_to_cpu(extent->length));
> > + xa_erase(&mds->pending_extents, index);
> > + kfree(extent);
> > + continue;
> > + }
> > + cnt++;
> > + }
> > + rc = cxl_send_dc_response(mds, CXL_MBOX_OP_ADD_DC_RESPONSE,
> > + &mds->pending_extents, cnt);
> > + xa_for_each(&mds->pending_extents, index, extent) {
> > + xa_erase(&mds->pending_extents, index);
> > + kfree(extent);
> > + }
> > + return rc;
> > +}
> > +
> > +static int handle_add_event(struct cxl_memdev_state *mds,
> > + struct cxl_event_dcd *event)
> > +{
> > + struct cxl_extent *tmp = kzalloc(sizeof(*tmp), GFP_KERNEL);
> > + struct device *dev = mds->cxlds.dev;
> > +
> > + if (!tmp)
> > + return -ENOMEM;
> > +
> > + memcpy(tmp, &event->extent, sizeof(*tmp));
>
> kmemdup?

yep.

>
> > + if (xa_insert(&mds->pending_extents, (unsigned long)tmp, tmp,
> > + GFP_KERNEL)) {
> > + kfree(tmp);
> > + return -ENOMEM;
> > + }
> > +
> > + if (event->flags & CXL_DCD_EVENT_MORE) {
> > + dev_dbg(dev, "more bit set; delay the surfacing of extent\n");
> > + return 0;
> > + }
> > +
> > + /* extents are removed and free'ed in cxl_add_pending() */
> > + return cxl_add_pending(mds);
> > +}
>
> > static void cxl_mem_get_records_log(struct cxl_memdev_state *mds,
> > enum cxl_event_log_type type)
> > {
> > @@ -1044,9 +1287,17 @@ static void cxl_mem_get_records_log(struct cxl_memdev_state *mds,
> > if (!nr_rec)
> > break;
> >
> > - for (i = 0; i < nr_rec; i++)
> > + for (i = 0; i < nr_rec; i++) {
> > __cxl_event_trace_record(cxlmd, type,
> > &payload->records[i]);
> > + if (type == CXL_EVENT_TYPE_DCD) {
> Bit of a deep indent so maybe flip logic?
>
> Logic wise it's a bit dubious as we might want to match other
> types in future though so up to you.

I was thinking more along these lines. But the rc is unneeded. That print
can be in the handle function.

Something like this:

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 88b823afe482..e86a483d80eb 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -1231,16 +1231,17 @@ static char *cxl_dcd_evt_type_str(u8 type)
return "<unknown>";
}

-static int cxl_handle_dcd_event_records(struct cxl_memdev_state *mds,
+static void cxl_handle_dcd_event_records(struct cxl_memdev_state *mds,
struct cxl_event_record_raw *raw_rec)
{
struct cxl_event_dcd *event = &raw_rec->event.dcd;
struct cxl_extent *extent = &event->extent;
struct device *dev = mds->cxlds.dev;
uuid_t *id = &raw_rec->id;
+ int rc;

if (!uuid_equal(id, &CXL_EVENT_DC_EVENT_UUID))
- return -EINVAL;
+ return;

dev_dbg(dev, "DCD event %s : DPA:%#llx LEN:%#llx\n",
cxl_dcd_evt_type_str(event->event_type),
@@ -1248,15 +1249,22 @@ static int cxl_handle_dcd_event_records(struct cxl_memdev_state *mds,

switch (event->event_type) {
case DCD_ADD_CAPACITY:
- return handle_add_event(mds, event);
+ rc = handle_add_event(mds, event);
+ break;
case DCD_RELEASE_CAPACITY:
- return cxl_rm_extent(mds, &event->extent);
+ rc = cxl_rm_extent(mds, &event->extent);
+ break;
case DCD_FORCED_CAPACITY_RELEASE:
dev_err_ratelimited(dev, "Forced release event ignored.\n");
- return 0;
+ rc = 0;
+ break;
default:
- return -EINVAL;
+ rc = -EINVAL;
+ break;
}
+
+ if (rc)
+ dev_err_ratelimited(dev, "dcd event failed: %d\n", rc);
}

static void cxl_mem_get_records_log(struct cxl_memdev_state *mds,
@@ -1297,13 +1305,9 @@ static void cxl_mem_get_records_log(struct cxl_memdev_state *mds,
for (i = 0; i < nr_rec; i++) {
__cxl_event_trace_record(cxlmd, type,
&payload->records[i]);
- if (type == CXL_EVENT_TYPE_DCD) {
- rc = cxl_handle_dcd_event_records(mds,
- &payload->records[i]);
- if (rc)
- dev_err_ratelimited(dev, "dcd event failed: %d\n",
- rc);
- }
+ if (type == CXL_EVENT_TYPE_DCD)
+ cxl_handle_dcd_event_records(mds,
+ &payload->records[i]);
}

if (payload->flags & CXL_GET_EVENT_FLAG_OVERFLOW)
<end diff>

>
> if (type != CXL_EVENT_TYPE_DCD)
> continue;
>
> rc =
>
> > + rc = cxl_handle_dcd_event_records(mds,
> > + &payload->records[i]);
> > + if (rc)
> > + dev_err_ratelimited(dev, "dcd event failed: %d\n",
> > + rc);
> > + }
> > + }
> >
>
> > struct cxl_memdev_state *cxl_memdev_state_create(struct device *dev)
> > {
> > struct cxl_memdev_state *mds;
> > @@ -1628,6 +1892,8 @@ struct cxl_memdev_state *cxl_memdev_state_create(struct device *dev)
> > mds->cxlds.type = CXL_DEVTYPE_CLASSMEM;
> > mds->ram_perf.qos_class = CXL_QOS_CLASS_INVALID;
> > mds->pmem_perf.qos_class = CXL_QOS_CLASS_INVALID;
> > + xa_init(&mds->pending_extents);
> > + devm_add_action_or_reset(dev, clear_pending_extents, mds);
>
> Why don't you need to check if this failed? Definitely seems unlikely
> to leave things in a good state. Unlikely to fail of course, but you never know.

yea good catch.

>
> >
> > return mds;
> > }
>
> > @@ -3090,6 +3091,8 @@ static struct cxl_dax_region *cxl_dax_region_alloc(struct cxl_region *cxlr)
> >
> > dev = &cxlr_dax->dev;
> > cxlr_dax->cxlr = cxlr;
> > + cxlr->cxlr_dax = cxlr_dax;
> > + ida_init(&cxlr_dax->extent_ida);
> > device_initialize(dev);
> > lockdep_set_class(&dev->mutex, &cxl_dax_region_key);
> > device_set_pm_not_required(dev);
> > @@ -3190,7 +3193,10 @@ static int devm_cxl_add_pmem_region(struct cxl_region *cxlr)
> > static void cxlr_dax_unregister(void *_cxlr_dax)
> > {
> > struct cxl_dax_region *cxlr_dax = _cxlr_dax;
> > + struct cxl_region *cxlr = cxlr_dax->cxlr;
> >
> > + cxlr->cxlr_dax = NULL;
> > + cxlr_dax->cxlr = NULL;
>
> cxlr_dax->cxlr was assigned before this patch.
>
> I'm not seeing any new checks on these being non null so why
> are the needed? If there is a good reason for this then
> a comment would be useful.

I'm not sure anymore either. Perhaps this was left over from an earlier
version. Or was something I thought I would need that ended up getting
removed. I'll test without this hunk and remove it if I can.

Thanks for the review,
Ira

[snip]