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cxl: Remove the CXL_DECODER_MIXED mistake

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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: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alejandro Lucero <alucerop@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Tested-by: Alejandro Lucero <alucerop@amd.com>
Link: https://patch.msgid.link/173864304660.668823.17000888505587850279.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
This commit is contained in:
Dan Williams 2025-02-03 20:24:06 -08:00 • committed by Dave Jiang
parent 2014c95afe
commit 188e9529a6
3 changed files with 4 additions and 18 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
drivers/cxl/core/hdm.c
View file

@ -332,9 +332,9 @@ static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
else if (resource_contains(&cxlds->ram_res, res)) else if (resource_contains(&cxlds->ram_res, res))
cxled->mode = CXL_DECODER_RAM; cxled->mode = CXL_DECODER_RAM;
else { else {
dev_warn(dev, "decoder%d.%d: %pr mixed mode not supported\n", dev_warn(dev, "decoder%d.%d: %pr does not map any partition\n",
port->id, cxled->cxld.id, cxled->dpa_res); port->id, cxled->cxld.id, res);
cxled->mode = CXL_DECODER_MIXED; cxled->mode = CXL_DECODER_NONE;
} }
port->hdm_end++; port->hdm_end++;

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

@ -2738,18 +2738,6 @@ static int poison_by_decoder(struct device *dev, void *arg)
if (!cxled->dpa_res || !resource_size(cxled->dpa_res)) if (!cxled->dpa_res || !resource_size(cxled->dpa_res))
return rc; 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); cxlmd = cxled_to_memdev(cxled);
if (cxled->skip) { if (cxled->skip) {
offset = cxled->dpa_res->start - cxled->skip; offset = cxled->dpa_res->start - cxled->skip;

4
drivers/cxl/cxl.h
View file

@ -380,7 +380,6 @@ enum cxl_decoder_mode {
CXL_DECODER_NONE, CXL_DECODER_NONE,
CXL_DECODER_RAM, CXL_DECODER_RAM,
CXL_DECODER_PMEM, CXL_DECODER_PMEM,
CXL_DECODER_MIXED,
CXL_DECODER_DEAD, 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_NONE] = "none",
[CXL_DECODER_RAM] = "ram", [CXL_DECODER_RAM] = "ram",
[CXL_DECODER_PMEM] = "pmem", [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 names[mode];
return "mixed"; return "mixed";
} }