Commit 188e9529 authored by Dan Williams's avatar Dan Williams Committed by Dave Jiang
Browse files

cxl: Remove the CXL_DECODER_MIXED mistake 



CXL_DECODER_MIXED is a safety mechanism introduced for the case where
platform firmware has programmed an endpoint decoder that straddles a
DPA partition boundary. While the kernel is careful to only allocate DPA
capacity within a single partition there is no guarantee that platform
firmware, or anything that touched the device before the current kernel,
gets that right.

However, __cxl_dpa_reserve() will never get to the CXL_DECODER_MIXED
designation because of the way it tracks partition boundaries. A
request_resource() that spans ->ram_res and ->pmem_res fails with the
following signature:

    __cxl_dpa_reserve: cxl_port endpoint15: decoder15.0: failed to reserve allocation

CXL_DECODER_MIXED is dead defensive programming after the driver has
already given up on the device. It has never offered any protection in
practice, just delete it.

Reviewed-by: default avatarIra Weiny <ira.weiny@intel.com>
Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: default avatarAlejandro Lucero <alucerop@amd.com>
Reviewed-by: default avatarDave Jiang <dave.jiang@intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Reviewed-by: default avatarFan Ni <fan.ni@samsung.com>
Tested-by: default avatarAlejandro Lucero <alucerop@amd.com>
Link: https://patch.msgid.link/173864304660.668823.17000888505587850279.stgit@dwillia2-xfh.jf.intel.com


Signed-off-by: default avatarDave Jiang <dave.jiang@intel.com>
parent 2014c95a

drivers/cxl/core/hdm.c

+3 −3
Original line number Diff line number Diff line
@@ -332,9 +332,9 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled, 
	else if (resource_contains(&cxlds->ram_res, res))

		cxled->mode = CXL_DECODER_RAM;

	else {

		dev_warn(dev, "decoder%d.%d: %pr mixed mode not supported\n",

			 port->id, cxled->cxld.id, cxled->dpa_res);

		cxled->mode = CXL_DECODER_MIXED;

		dev_warn(dev, "decoder%d.%d: %pr does not map any partition\n",

			 port->id, cxled->cxld.id, res);

		cxled->mode = CXL_DECODER_NONE;

	}



	port->hdm_end++;

drivers/cxl/core/region.c

+0 −12
Original line number Diff line number Diff line
@@ -2738,18 +2738,6 @@ static int poison_by_decoder(struct device *dev, void *arg) 
	if (!cxled->dpa_res || !resource_size(cxled->dpa_res))

		return rc;



	/*

	 * Regions are only created with single mode decoders: pmem or ram.

	 * Linux does not support mixed mode decoders. This means that

	 * reading poison per endpoint decoder adheres to the requirement

	 * that poison reads of pmem and ram must be separated.

	 * CXL 3.0 Spec 8.2.9.8.4.1

	 */

	if (cxled->mode == CXL_DECODER_MIXED) {

		dev_dbg(dev, "poison list read unsupported in mixed mode\n");

		return rc;

	}



	cxlmd = cxled_to_memdev(cxled);

	if (cxled->skip) {

		offset = cxled->dpa_res->start - cxled->skip;

drivers/cxl/cxl.h

+1 −3
Original line number Diff line number Diff line
@@ -380,7 +380,6 @@ enum cxl_decoder_mode { 
	CXL_DECODER_NONE,

	CXL_DECODER_RAM,

	CXL_DECODER_PMEM,

	CXL_DECODER_MIXED,

	CXL_DECODER_DEAD,

};
@@ -390,10 +389,9 @@ static inline const char *cxl_decoder_mode_name(enum cxl_decoder_mode mode) 
		[CXL_DECODER_NONE] = "none",

		[CXL_DECODER_RAM] = "ram",

		[CXL_DECODER_PMEM] = "pmem",

		[CXL_DECODER_MIXED] = "mixed",

	};



	if (mode >= CXL_DECODER_NONE && mode <= CXL_DECODER_MIXED)

	if (mode >= CXL_DECODER_NONE && mode < CXL_DECODER_DEAD)

		return names[mode];

	return "mixed";

}