Message-ID: <ZBiwMbYBShBjuhW2@aschofie-mobl2>
Date:   Mon, 20 Mar 2023 12:12:49 -0700
From:   Alison Schofield <alison.schofield@...el.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 4/6] cxl/region: Provide region info to the cxl_poison
 trace event

On Mon, Mar 20, 2023 at 03:53:06PM +0000, Jonathan Cameron wrote:
> On Sun, 19 Mar 2023 21:31:49 -0700
> alison.schofield@...el.com wrote:
> 
> > From: Alison Schofield <alison.schofield@...el.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 region driver
> > reads the poison list for all the mapped resources, control returns
> > to the memdev driver, where poison is read for any remaining unmapped
> > resources.
> > 
> > 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@...el.com>
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Hi Alison,
> 
> I could be wrong but I don't think I gave a reviewed-by for this individual patch
> (I made a note locally that I still needed to test v8 before doing so).
> Doesn't matter in the end though..
> 
> Tested-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> + keep the RB.
> 
> A few whitespace changes have sneaked in here though that would be good to 
> clean up. (inline)

Jonathan,

My apologies for applying the reviewed by tag.
Thanks for the tags now

I'll clean up the whitespace and try to keep it that way. There's 
something about the spacing around returns, that my subconscious
struggles with. I'm not deliberately ignoring you ;)

Alison

> 
> Thanks,
> 
> Jonathan
> 
> > ---
> >  drivers/cxl/core/core.h   | 11 +++++++
> >  drivers/cxl/core/memdev.c | 64 +++++++++++++++++++++++++++++++++++++--
> >  drivers/cxl/core/region.c | 63 ++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 136 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> > index cde475e13216..3d1b38255ab4 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)
> >  {
> >  }
> > @@ -64,4 +69,10 @@ int cxl_memdev_init(void);
> >  void cxl_memdev_exit(void);
> >  void cxl_mbox_init(void);
> >  
> > +struct cxl_trigger_poison_context {
> > +	struct cxl_port *port;
> > +	enum cxl_decoder_mode mode;
> > +	u64 offset;
> > +};
> > +
> >  #endif /* __CXL_CORE_H__ */
> > diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> > index 5ef40c36f1a3..0b8b8996e588 100644
> > --- a/drivers/cxl/core/memdev.c
> > +++ b/drivers/cxl/core/memdev.c
> > @@ -106,6 +106,47 @@ static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr,
> >  }
> >  static DEVICE_ATTR_RO(numa_node);
> >  
> > +static int cxl_get_poison_unmapped(struct cxl_memdev *cxlmd,
> > +				   struct cxl_trigger_poison_context *ctx)
> > +{
> > +	struct cxl_dev_state *cxlds = cxlmd->cxlds;
> > +	u64 offset, length;
> > +	int rc = 0;
> > +
> > +	/*
> > +	 * Collect poison for the remaining unmapped resources
> > +	 * after poison is collected by committed endpoints.
> > +	 *
> > +	 * Knowing that PMEM must always follow RAM, get poison
> > +	 * for unmapped resources based on the last decoder's mode:
> > +	 *	ram: scan remains of ram range, then any pmem range
> > +	 *	pmem: scan remains of pmem range
> > +	 */
> > +
> > +	if (ctx->mode == CXL_DECODER_RAM) {
> > +		offset = ctx->offset;
> > +		length = resource_size(&cxlds->ram_res) - offset;
> > +		rc = cxl_mem_get_poison(cxlmd, offset, length, NULL);
> > +		if (rc == -EFAULT)
> > +			rc = 0;
> > +		if (rc)
> > +			return rc;
> > +	}
> > +	if (ctx->mode == CXL_DECODER_PMEM) {
> > +		offset = ctx->offset;
> > +		length = resource_size(&cxlds->dpa_res) - offset;
> > +		if (!length)
> > +			return 0;
> > +	} else if (resource_size(&cxlds->pmem_res)) {
> > +		offset = cxlds->pmem_res.start;
> > +		length = resource_size(&cxlds->pmem_res);
> > +	} else {
> > +		return 0;
> > +	}
> > +
> > +	return cxl_mem_get_poison(cxlmd, offset, length, NULL);
> > +}
> > +
> >  static int cxl_get_poison_by_memdev(struct cxl_memdev *cxlmd)
> >  {
> >  	struct cxl_dev_state *cxlds = cxlmd->cxlds;
> > @@ -139,17 +180,36 @@ ssize_t cxl_trigger_poison_list(struct device *dev,
> >  				const char *buf, size_t len)
> >  {
> >  	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
> > +	struct cxl_trigger_poison_context ctx;
> > +	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 */
> > +		ctx = (struct cxl_trigger_poison_context) {
> > +			.port = port,
> > +		};
> > +		rc = device_for_each_child(&port->dev, &ctx,
> > +					   cxl_get_poison_by_endpoint);
> > +		if (rc == 1)
> > +			rc = cxl_get_poison_unmapped(cxlmd, &ctx);
> > +	}
> > +
> >  	up_read(&cxl_dpa_rwsem);
> > -
> I'd keep this one.
> >  	return rc ? rc : len;
> > +
> Doesn't want to be here.
> 
> >  }
> >  EXPORT_SYMBOL_NS_GPL(cxl_trigger_poison_list, CXL);
> >  
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index f29028148806..4c4d3a6d631d 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -2213,6 +2213,69 @@ 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 *arg)
> > +{
> > +	struct cxl_trigger_poison_context *ctx = arg;
> > +	struct cxl_endpoint_decoder *cxled;
> > +	struct cxl_port *port = ctx->port;
> > +	struct cxl_memdev *cxlmd;
> > +	u64 offset, length;
> > +	int rc = 0;
> > +
> > +	down_read(&cxl_region_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) {
> > +		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;
> > +	}
> > +
> > +	offset = cxled->dpa_res->start;
> > +	length = cxled->dpa_res->end - offset + 1;
> > +	rc = cxl_mem_get_poison(cxlmd, offset, 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)
> > +		rc = 1;
> > +
> > +	/* ctx informs the memdev driver of last read poison */
> > +	ctx->mode = cxled->mode;
> > +	ctx->offset = cxled->dpa_res->end + 1;
> > +out:
> > +	up_read(&cxl_region_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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