Messages in this thread Patch in this message | | | Date | Fri, 3 Mar 2023 21:51:50 -0800 | From | Alison Schofield <> | Subject | Re: [PATCH v7 4/6] cxl/region: Provide region info to the cxl_poison trace event |
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On Fri, Mar 03, 2023 at 09:35:06AM -0800, Alison Schofield wrote: > On Fri, Mar 03, 2023 at 04:46:58PM +0000, Jonathan Cameron wrote: > > On Fri, 17 Feb 2023 18:18:52 -0800 > > alison.schofield@intel.com wrote: > > > > > From: Alison Schofield <alison.schofield@intel.com> > > > > > > User space may need to know which region, if any, maps the poison > > > address(es) logged in a cxl_poison trace event. Since the mapping > > > of DPAs (device physical addresses) to a region can change, the > > > kernel must provide this information at the time the poison list > > > is read. The event informs user space that at event <timestamp> > > > this <region> mapped to this <DPA>, which is poisoned. > > > > > > The cxl_poison trace event is already wired up to log the region > > > name and uuid if it receives param 'struct cxl_region'. > > > > > > In order to provide that cxl_region, add another method for gathering > > > poison - by committed endpoint decoder mappings. This method is only > > > available with CONFIG_CXL_REGION and is only used if a region actually > > > maps the memdev where poison is being read. After the poison list is > > > read for all the mapped resources, poison is read for the unmapped > > > resources, and those events are logged without the region info. > > > > > > Mixed mode decoders are not currently supported in Linux. Add a debug > > > message to the poison request path. That will serve as an alert that > > > poison list retrieval needs to add support for mixed mode. > > > > > > The default method remains: read the poison by memdev resource. > > > > > > Signed-off-by: Alison Schofield <alison.schofield@intel.com> > > Hi Alison, > > > > I decided to give this a test run on to of a single emulated direct > > attached EP with both persistent and volatile memory, but only > > part of each added to a region (so we get a skip). > > This looks like issues with 'unsupported' mixed mode decoders. > How are you getting past the mixed mode decoder check?
Ignore the above mixed mode decoder question.
This logic below is what I'm thinking, and coding too, but I dont' think it's related to the issues you saw.
I've looked at each issue below, and think I've fixed. See inline...
> > Is there a logic error here: > > A device paritioned into ram and pmem, may have: > zero or more ram decodes > followed by zero or one skip > followed by zero or more pmem decodes > followed by maybe unused space > > So EPs may look like these: > ram-01, ram-02, skip-pmem-03, pmem-04 > skip-pmem-01, pmem-02 > > But never these: (no multiple skips and only skip over ram) > ram-01, skip-ram-02, skip-pmem-03 > skip-pmem-01, skip-pmem-02, > > I'm still looking at the snippets below. > > Thanks, > Jonathan > > > > > Without regions it all works as expected. With them not so much - see inline > > > > region uuid is also a bit pointless for volatile regions as I think > > current code makes it all 0s.
Are you referring to the cxl_poison trace_event?
The region_uuid field is being included as standard, for all cxl_poison events. So, events without region-uuids, which includes ram regions, and plain memdevs, will get the annoyingly region_uuid=0000000000000000000000000.
Is that bothering you ?
> > > > Jonathan > > > > > > > --- > > > drivers/cxl/core/core.h | 5 +++ > > > drivers/cxl/core/memdev.c | 14 +++++- > > > drivers/cxl/core/region.c | 89 +++++++++++++++++++++++++++++++++++++++ > > > 3 files changed, 107 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h > > > index cde475e13216..4f507cb85926 100644 > > > --- a/drivers/cxl/core/core.h > > > +++ b/drivers/cxl/core/core.h > > > @@ -25,7 +25,12 @@ void cxl_decoder_kill_region(struct cxl_endpoint_decoder *cxled); > > > #define CXL_DAX_REGION_TYPE(x) (&cxl_dax_region_type) > > > int cxl_region_init(void); > > > void cxl_region_exit(void); > > > +int cxl_get_poison_by_endpoint(struct device *dev, void *data); > > > #else > > > +static inline int cxl_get_poison_by_endpoint(struct device *dev, void *data) > > > +{ > > > + return 0; > > > +} > > > static inline void cxl_decoder_kill_region(struct cxl_endpoint_decoder *cxled) > > > { > > > } > > > diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c > > > index ea996057815e..c11b7bc253b4 100644 > > > --- a/drivers/cxl/core/memdev.c > > > +++ b/drivers/cxl/core/memdev.c > > > @@ -139,14 +139,26 @@ static ssize_t trigger_poison_list_store(struct device *dev, > > > const char *buf, size_t len) > > > { > > > struct cxl_memdev *cxlmd = to_cxl_memdev(dev); > > > + struct cxl_port *port; > > > bool trigger; > > > int rc; > > > > > > if (kstrtobool(buf, &trigger) || !trigger) > > > return -EINVAL; > > > > > > + port = dev_get_drvdata(&cxlmd->dev); > > > + if (!port || !is_cxl_endpoint(port)) > > > + return -EINVAL; > > > + > > > down_read(&cxl_dpa_rwsem); > > > - rc = cxl_get_poison_by_memdev(cxlmd); > > > + if (port->commit_end == -1) > > > + /* No regions mapped to this memdev */ > > > + rc = cxl_get_poison_by_memdev(cxlmd); > > > + else > > > + /* Regions mapped, collect poison by endpoint */ > > > + rc = device_for_each_child(&port->dev, port, > > > + cxl_get_poison_by_endpoint); > > > > So this had me confused for a while. If I setup a couple of regions > > on a mixed device with a skip between (may happen anyway) > > then this returns 1 which is not what we are aiming for. > > > > Chasing it through we are reaching the last part of > > cxl_get_poison_by_endpoint() which has the comment > > "... Return rc or 1 to stop iteration." which is exactly > > what it is doing. > > > > so need an if (rc == 1) rc = 0; here
Thanks for the catch. I fixed up as you suggested, so that only (-rc)'s pass onward.
> > > > > > > > > + > > > up_read(&cxl_dpa_rwsem); > > > > > > return rc ? rc : len; > > > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c > > > index f29028148806..a055f8e36ef1 100644 > > > --- a/drivers/cxl/core/region.c > > > +++ b/drivers/cxl/core/region.c > > > @@ -2213,6 +2213,95 @@ struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev) > > > } > > > EXPORT_SYMBOL_NS_GPL(to_cxl_pmem_region, CXL); > > > > > > +int cxl_get_poison_by_endpoint(struct device *dev, void *data) > > > +{ > > > + struct cxl_endpoint_decoder *cxled; > > > + struct cxl_port *port = data; > > > + struct cxl_dev_state *cxlds; > > > + struct cxl_memdev *cxlmd; > > > + u64 offset, length; > > > + int rc = 0; > > > + > > > + down_read(&cxl_dpa_rwsem); > > > + > > > + if (!is_endpoint_decoder(dev)) > > > + goto out; > > > + > > > + cxled = to_cxl_endpoint_decoder(dev); > > > + if (!cxled->dpa_res || !resource_size(cxled->dpa_res)) > > > + goto out; > > > + > > > + /* > > > + * Regions are only created with single mode decoders: pmem or ram. > > > + * Linux does not currently support mixed mode decoders. This means > > > + * that reading poison per endpoint decoder adheres to the spec > > > + * requirement that poison reads of pmem and ram must be separated. > > > + * CXL 3.0 Spec 8.2.9.8.4.1 > > > + * > > > + * Watch for future support of mixed with a dev_dbg() msg. > > > + */ > > > + if (cxled->mode == CXL_DECODER_MIXED) { > > > + dev_dbg(dev, "poison list read unsupported in mixed mode\n"); > > > + goto out; > > > + } > > > + > > > + cxlmd = cxled_to_memdev(cxled); > > > + if (cxled->skip) { > > > + rc = cxl_mem_get_poison(cxlmd, 0, cxled->skip, NULL); > > > > The base of this should be the top fo the previous decoder. I'm not immediately > > sure how you can get hold of that.
I had only consdired and coded for the case where the skip was at the start of the cxlds resource. This diff below works because the cxled->skip is telling us the length that was skipped over to get to this decoder.
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index a055f8e36ef1..9ba7cfbdaca8 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -2247,15 +2247,19 @@ int cxl_get_poison_by_endpoint(struct device *dev, void *data)
cxlmd = cxled_to_memdev(cxled); if (cxled->skip) { - rc = cxl_mem_get_poison(cxlmd, 0, cxled->skip, NULL); + offset = cxled->dpa_res->start - cxled->skip; + length = cxled->skip; + rc = cxl_mem_get_poison(cxlmd, offset, length, NULL); if (rc == -EFAULT && cxled->mode == CXL_DECODER_RAM) rc = 0; if (rc) goto out; }
Test case showing ram decode followed by a few pmem decodes:
cxl decoder8.0: cxl_get_poison_by_endpoint: endpoint: decoder8.0 cxl_mem mem0: region:region2 offset: 0x0 len: 0x10000000
cxl decoder8.1: cxl_get_poison_by_endpoint: endpoint: decoder8.1 cxl decoder8.1: cxl_get_poison_by_endpoint: SKIP FOUND cxl_mem mem0: region:No_Region offset: 0x10000000 len: 0x30000000 (above is reading poison for the skip) cxl_mem mem0: region:region4 offset: 0x40000000 len: 0x10000000
cxl decoder8.2: cxl_get_poison_by_endpoint: endpoint: decoder8.2 cxl_mem mem0: region:region9 offset: 0x50000000 len: 0x10000000
cxl decoder8.3: cxl_get_poison_by_endpoint: endpoint: decoder8.3 cxl_mem mem0: region:region10 offset: 0x60000000 len: 0x10000000
> > In my test with 1GB volatile and 1GB persistent the queries that are sent are: > > 0 to 0x10000000 (correct) > > 0 to 0x30000000 (wrong start, should be 0x10000000) > > > > 0x40000000 to 0x50000000 (correct) > > 0x50000000 to 0x40000000 (not correct but at least the start is correct). > > See below for this one. > > > > > + if (rc == -EFAULT && cxled->mode == CXL_DECODER_RAM) > > > + rc = 0; > > > + if (rc) > > > + goto out; > > > + } > > > + length = cxled->dpa_res->end - cxled->dpa_res->start + 1; > > > + rc = cxl_mem_get_poison(cxlmd, cxled->dpa_res->start, length, > > > + cxled->cxld.region); > > > + if (rc == -EFAULT && cxled->mode == CXL_DECODER_RAM) > > > + rc = 0; > > > + if (rc) > > > + goto out; > > > + > > > + /* Iterate until commit_end is reached */ > > > + if (cxled->cxld.id < port->commit_end) > > > + goto out; > > > + > > > + /* > > > + * Reach here with the last committed decoder only. > > > + * Knowing that PMEM must always follow RAM, get poison > > > + * for unmapped ranges based on the last decoder's mode: > > > + * ram: scan remains of ram range, then scan for pmem > > > + * pmem: scan remains of pmem range > > > + */ > > > + cxlds = cxlmd->cxlds; > > > + > > > + if (cxled->mode == CXL_DECODER_RAM) { > > > + offset = cxled->dpa_res->end + 1; > > > + length = resource_size(&cxlds->ram_res) - offset; > > > + rc = cxl_mem_get_poison(cxlmd, offset, length, NULL); > > > + if (rc == -EFAULT) > > > + rc = 0; > > > + if (rc) > > > + goto out; > > > + } > > > + if (cxled->mode == CXL_DECODER_PMEM) { > > > + offset = cxled->dpa_res->end + 1; > > > > This is fine, unless you have a ram region in which case > > the offset computed here includes that as well as the > > persistent bit. > > > > > + length = resource_size(&cxlds->pmem_res) - offset; > > > > So you need to take that into account with something like > > - (offset - cxlds->pmem_res.start); > >
I think this is corrected by using the cxlds->dpa_res in the length calculation. And then, there could be no remains, hence the length check.
if (cxled->mode == CXL_DECODER_PMEM) { offset = cxled->dpa_res->end + 1; - length = resource_size(&cxlds->pmem_res) - offset; + length = resource_size(&cxlds->dpa_res) - offset; + if (!length) { + rc = 1; + goto out; + }
I'm going to give these changes a more thorough testing and add more test cases before posting the next version.
Thanks for the test and review!
Alison
> > > + } else if (resource_size(&cxlds->pmem_res)) { > > > + offset = cxlds->pmem_res.start; > > > + length = resource_size(&cxlds->pmem_res); > > > + } else { > > > + rc = 1; > > > + goto out; > > > + } > > > + /* Final get poison call. Return rc or 1 to stop iteration. */ > > > + rc = cxl_mem_get_poison(cxlmd, offset, length, NULL); > > > + if (!rc) > > > + rc = 1; > > > +out: > > > + up_read(&cxl_dpa_rwsem); > > > + return rc; > > > +} > > > + > > > static struct lock_class_key cxl_pmem_region_key; > > > > > > static struct cxl_pmem_region *cxl_pmem_region_alloc(struct cxl_region *cxlr) > >
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