RE: [PATCH v8 03/14] cxl/hdm: Use stored Component Register mappings to map HDM decoder capability

[Dan Williams]

Terry Bowman wrote:
> From: Robert Richter <rrichter@xxxxxxx>
> 
> Now, that the Component Register mappings are stored, use them to
> enable and map the HDM decoder capabilities. The Component Registers
> do not need to be probed again for this, remove probing code.
> 
> The HDM capability applies to Endpoints, USPs and VH Host Bridges. The
> Endpoint's component register mappings are located in the cxlds and
> else in the port's structure. Provide a helper function
> cxl_port_get_comp_map() to locate the mappings depending on the
> component's type.

This causes a regression that cxl_test tripped over. It's likely
something you could reproduce without cxl_test just be reloading the
cxl_port driver. Root cause below, but here is what I see on a test run:

# meson test -C build --suite cxl
ninja: no work to do.
ninja: Entering directory `/root/git/ndctl/build'
[113/113] Linking target ndctl/ndctl
1/6 ndctl:cxl / cxl-topology.sh             OK              12.78s
2/6 ndctl:cxl / cxl-region-sysfs.sh         OK               7.72s
3/6 ndctl:cxl / cxl-labels.sh               FAIL             1.53s   (exit status 129 or signal 1 SIGHUP)
>>> LD_LIBRARY_PATH=/root/git/ndctl/build/cxl/lib:/root/git/ndctl/build/ndctl/lib:/root/git/ndctl/build/daxctl/lib NDCTL=/root/git/ndctl/build/ndctl/ndctl DAXCTL=/root/git/ndctl/build/daxctl/daxctl MALLOC_PERTURB_=67 TEST_PATH=/root/git/ndctl/build/test DATA_PATH=/root/git/ndctl/test /bin/bash /root/git/ndctl/test/cxl-labels.sh

4/6 ndctl:cxl / cxl-create-region.sh        OK              17.05s
5/6 ndctl:cxl / cxl-xor-region.sh           OK               5.18s
6/6 ndctl:cxl / cxl-security.sh             OK               4.68s

Ok:                 5   
Expected Fail:      0   
Fail:               1   
Unexpected Pass:    0   
Skipped:            0   
Timeout:            0   

Full log written to /root/git/ndctl/build/meson-logs/testlog.txt

It's not that cxl-labels.sh causes the error, it is loading and
unloading the port driver trips over the problem below:

> 
> Signed-off-by: Robert Richter <rrichter@xxxxxxx>
> Signed-off-by: Terry Bowman <terry.bowman@xxxxxxx>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> ---
>  drivers/cxl/core/hdm.c | 64 +++++++++++++++++++++++-------------------
>  1 file changed, 35 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 4449b34a80cc..b0f59e63e0d2 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -81,26 +81,6 @@ static void parse_hdm_decoder_caps(struct cxl_hdm *cxlhdm)
>  		cxlhdm->interleave_mask |= GENMASK(14, 12);
>  }
>  
> -static int map_hdm_decoder_regs(struct cxl_port *port, void __iomem *crb,
> -				struct cxl_component_regs *regs)
> -{
> -	struct cxl_register_map map = {
> -		.dev = &port->dev,
> -		.resource = port->component_reg_phys,
> -		.base = crb,
> -		.max_size = CXL_COMPONENT_REG_BLOCK_SIZE,
> -	};
> -
> -	cxl_probe_component_regs(&port->dev, crb, &map.component_map);
> -	if (!map.component_map.hdm_decoder.valid) {
> -		dev_dbg(&port->dev, "HDM decoder registers not implemented\n");
> -		/* unique error code to indicate no HDM decoder capability */
> -		return -ENODEV;
> -	}
> -
> -	return cxl_map_component_regs(&map, regs, BIT(CXL_CM_CAP_CAP_ID_HDM));
> -}
> -
>  static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
>  {
>  	struct cxl_hdm *cxlhdm;
> @@ -145,6 +125,22 @@ static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
>  	return true;
>  }
>  
> +static struct cxl_register_map *cxl_port_get_comp_map(struct cxl_port *port)
> +{
> +	/*
> +	 * HDM capability applies to Endpoints, USPs and VH Host
> +	 * Bridges. The Endpoint's component register mappings are
> +	 * located in the cxlds.
> +	 */
> +	if (is_cxl_endpoint(port)) {
> +		struct cxl_memdev *memdev = to_cxl_memdev(port->uport_dev);
> +
> +		return &memdev->cxlds->comp_map;

...but why? The issue here is that the @dev argument in that map is the
memdev parent PCI device. However, in this context the @dev for devm
operations wants to be &port->dev.

> +	}
> +
> +	return &port->comp_map;

...so this is fine, and folding in the following resolves the test
failure.

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index b0f59e63e0d2..6f111f487795 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -125,22 +125,6 @@ static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
        return true;
 }
 
-static struct cxl_register_map *cxl_port_get_comp_map(struct cxl_port *port)
-{
-       /*
-        * HDM capability applies to Endpoints, USPs and VH Host
-        * Bridges. The Endpoint's component register mappings are
-        * located in the cxlds.
-        */
-       if (is_cxl_endpoint(port)) {
-               struct cxl_memdev *memdev = to_cxl_memdev(port->uport_dev);
-
-               return &memdev->cxlds->comp_map;
-       }
-
-       return &port->comp_map;
-}
-
 /**
  * devm_cxl_setup_hdm - map HDM decoder component registers
  * @port: cxl_port to map
@@ -160,8 +144,7 @@ struct cxl_hdm *devm_cxl_setup_hdm(struct cxl_port *port,
        cxlhdm->port = port;
        dev_set_drvdata(dev, cxlhdm);
 
-       comp_map = cxl_port_get_comp_map(port);
-
+       comp_map = &port->comp_map;
        if (comp_map->resource == CXL_RESOURCE_NONE) {
                if (info && info->mem_enabled) {
                        cxlhdm->decoder_count = info->ranges;


Am I missing why the cxlds->comp_map needs to be reused?

Note that I am out and may not be able to respond further until next
week.