linux-kernel - [PATCH 3/3] cxl: Avoid to create dax regions for type2 accelerators

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Message-Id: <20240729084611.502889-4-ying.huang@intel.com>
Date: Mon, 29 Jul 2024 16:46:11 +0800
From: Huang Ying <ying.huang@...el.com>
To: Dan Williams <dan.j.williams@...el.com>,
	Dave Jiang <dave.jiang@...el.com>
Cc: linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Huang Ying <ying.huang@...el.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Jonathan Cameron <jonathan.cameron@...wei.com>,
	Alison Schofield <alison.schofield@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Ira Weiny <ira.weiny@...el.com>,
	Alejandro Lucero <alucerop@....com>
Subject: [PATCH 3/3] cxl: Avoid to create dax regions for type2 accelerators

The memory range of a type2 accelerator should be managed by the type2
accelerator specific driver instead of the common dax region drivers,
as discussed in [1].

[1] https://lore.kernel.org/linux-cxl/66469ff1b8fbc_2c2629427@dwillia2-xfh.jf.intel.com.notmuch/

So, in this patch, we skip dax regions creation for type2 accelerator
device memory regions.

Based on: https://lore.kernel.org/linux-cxl/168592159835.1948938.1647215579839222774.stgit@dwillia2-xfh.jf.intel.com/

Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
Co-developed-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: Jonathan Cameron <jonathan.cameron@...wei.com>
Cc: Dave Jiang <dave.jiang@...el.com>
Cc: Alison Schofield <alison.schofield@...el.com>
Cc: Vishal Verma <vishal.l.verma@...el.com>
Cc: Ira Weiny <ira.weiny@...el.com>
Cc: Alejandro Lucero <alucerop@....com>
---
 drivers/cxl/core/region.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 9a483c8a32fd..b37e12bb4a35 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3435,6 +3435,14 @@ static int cxl_region_probe(struct device *dev)
 					p->res->start, p->res->end, cxlr,
 					is_system_ram) > 0)
 			return 0;
+		/*
+		 * HDM-D[B] (device-memory) regions have accelerator
+		 * specific usage, skip device-dax registration.
+		 */
+		if (cxlr->type == CXL_DECODER_DEVMEM)
+			return 0;
+
+		/* HDM-H routes to device-dax */
 		return devm_cxl_add_dax_region(cxlr);
 	default:
 		dev_dbg(&cxlr->dev, "unsupported region mode: %d\n",
-- 
2.39.2