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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: 176baefb2e ("cxl/hdm: Commit decoder state to hardware")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/168696507423.3590522.16254212607926684429.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams 2023-06-16 18:24:34 -07:00
parent d1257d098a
commit 2ab47045ac
2 changed files with 20 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/cxl/core/region.c
View File

@ -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.

8
drivers/cxl/cxl.h
View File

@ -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