Commit 2ab47045 authored by Dan Williams's avatar Dan Williams
Browse files

cxl/region: Flag partially torn down regions as unusable 

cxl_region_decode_reset() walks all the decoders associated with a given
region and disables them. Due to decoder ordering rules it is possible
that a switch in the topology notices that a given decoder can not be
shutdown before another region with a higher HPA is shutdown first. That
can leave the region in a partially committed state.

Capture that state in a new CXL_REGION_F_NEEDS_RESET flag and require
that a successful cxl_region_decode_reset() attempt must be completed
before cxl_region_probe() accepts the region.

This is a corollary for the bug that Jonathan identified in "CXL/region
:  commit reset of out of order region appears to succeed." [1].

Cc: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Link: http://lore.kernel.org/r/20230316171441.0000205b@Huawei.com

 [1]
Fixes: 176baefb ("cxl/hdm: Commit decoder state to hardware")
Reviewed-by: default avatarDave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/168696507423.3590522.16254212607926684429.stgit@dwillia2-xfh.jf.intel.com


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent d1257d09

drivers/cxl/core/region.c

+12 −0
Original line number Diff line number Diff line
@@ -182,14 +182,19 @@ static int cxl_region_decode_reset(struct cxl_region *cxlr, int count) 
				rc = cxld->reset(cxld);

			if (rc)

				return rc;

			set_bit(CXL_REGION_F_NEEDS_RESET, &cxlr->flags);

		}



endpoint_reset:

		rc = cxled->cxld.reset(&cxled->cxld);

		if (rc)

			return rc;

		set_bit(CXL_REGION_F_NEEDS_RESET, &cxlr->flags);

	}



	/* all decoders associated with this region have been torn down */

	clear_bit(CXL_REGION_F_NEEDS_RESET, &cxlr->flags);



	return 0;

}
@@ -2864,6 +2869,13 @@ static int cxl_region_probe(struct device *dev) 
		goto out;

	}



	if (test_bit(CXL_REGION_F_NEEDS_RESET, &cxlr->flags)) {

		dev_err(&cxlr->dev,

			"failed to activate, re-commit region and retry\n");

		rc = -ENXIO;

		goto out;

	}



	/*

	 * From this point on any path that changes the region's state away from

	 * CXL_CONFIG_COMMIT is also responsible for releasing the driver.

drivers/cxl/cxl.h

+8 −0
Original line number Diff line number Diff line
@@ -469,6 +469,14 @@ struct cxl_region_params { 
 */

#define CXL_REGION_F_AUTO 0



/*

 * Require that a committed region successfully complete a teardown once

 * any of its associated decoders have been torn down. This maintains

 * the commit state for the region since there are committed decoders,

 * but blocks cxl_region_probe().

 */

#define CXL_REGION_F_NEEDS_RESET 1



/**

 * struct cxl_region - CXL region

 * @dev: This region's device